Refine
Has Fulltext
- yes (293)
Is part of the Bibliography
- yes (293)
Year of publication
Document Type
- Journal article (220)
- Doctoral Thesis (50)
- Book article / Book chapter (14)
- Conference Proceeding (6)
- Review (2)
- Preprint (1)
Language
- English (293) (remove)
Keywords
- Toxikologie (119)
- DNA damage (15)
- Adenosine receptors (9)
- Adenosinrezeptor (8)
- oxidative stress (7)
- DNS-Schädigung (6)
- GPCR (6)
- Genotoxicity (6)
- DNA (5)
- DNA binding (5)
- G-Protein gekoppelte Rezeptoren (5)
- Micronuclei (5)
- Pharmakologie (5)
- Adenylate cyclase (4)
- FRET (4)
- Fluoreszenz-Resonanz-Energie-Transfer (4)
- G proteins (4)
- Medizin (4)
- Oxidativer Stress (4)
- micronuclei (4)
- mycotoxin (4)
- 1 (3)
- Biotransformation (3)
- Carcinogen (3)
- Carcinogenesis (3)
- Carcinogenicity (3)
- Carcinogens (3)
- DNA-Schaden (3)
- ERK1/2 (3)
- Enzyme induction (3)
- Ernährung (3)
- G protein-coupled receptors (3)
- Pneumolysin (3)
- apoptosis (3)
- cAMP (3)
- cytoskeleton (3)
- genotoxicity (3)
- heart failure (3)
- inflammation (3)
- liver (3)
- metabolism (3)
- nephrotoxicity (3)
- signal transduction (3)
- transcription factors (3)
- 18F-FDG (2)
- 5-Azacytidine (2)
- A1 adenosine receptors (2)
- Adenosin (2)
- Adrenerger Rezeptor (2)
- Aldosteron (2)
- Ames test (2)
- Angiotensin II (2)
- Bakteriengift (2)
- Benzene (2)
- Carcinogenität (2)
- DNA Binding (2)
- DNA Schaden (2)
- DNA repair (2)
- Diethylstilbestrol (2)
- Dose response (2)
- Dose-response relationship (2)
- Electropermeabilization (2)
- Estrogen (2)
- FCS (2)
- Förster Resonanz Energie Transfer (2)
- G-Protein gekoppelter Rezeptor (2)
- G-protein (2)
- Genotoxizität (2)
- HPLC-MS (2)
- Herzhypertrophie (2)
- Hirnhautentzündung (2)
- Hormone (2)
- In vitro (2)
- Inhalation (2)
- Insulin (2)
- Kleinkern (2)
- Leber (2)
- Meningitis (2)
- Micronucleus (2)
- Muscarinrezeptor (2)
- Mutagenität (2)
- Myokarditis (2)
- N-formyl peptides (2)
- Niere (2)
- PET (2)
- Pharmakokinetik (2)
- Pharmazie (2)
- QIVIVE (2)
- RKIP (2)
- Radioligand binding (2)
- Rat (2)
- Reproductive toxicity (2)
- Risk Assessment (2)
- Salmonella/microsome assay (2)
- Silicones (2)
- Toxicology (2)
- Toxin (2)
- actin (2)
- actinomycetes (2)
- adenosine receptors (2)
- aldosterone (2)
- barbiturates (2)
- biased signaling (2)
- binding (2)
- biomedicine, general (2)
- cGMP (2)
- calcium (2)
- cancer risk (2)
- carcinogen (2)
- carcinogenicity (2)
- cardiac hypertrophy (2)
- cell biology (2)
- comet assay (2)
- cytokinins (2)
- dialysis (2)
- differentiation (2)
- environmental health (2)
- familial DCM (2)
- fluorescence (2)
- fluorescence resonance energy transfer (2)
- genomic damage (2)
- heart (2)
- iPSC-cardiomyocytes (2)
- immunohistochemistry (2)
- in-vivo (2)
- insulin (2)
- kidneys (2)
- lymphocytes (2)
- mast cells (2)
- medicine (2)
- membrane skeleton (2)
- meningitis (2)
- mercapturic acid (2)
- mutagenicity (2)
- myocarditis (2)
- occupational medicine/industrial medicine (2)
- pharmacogenetics (2)
- pharmacokinetics (2)
- pharmacology/toxicology (2)
- phosphorylation (2)
- pneumolysin (2)
- positron emission tomography (2)
- rat brain membranes (2)
- receptors (2)
- resveratrol (2)
- risk assessment (2)
- therapy (2)
- toxicity (2)
- uremic toxins (2)
- vitamin B6 (2)
- yam (2)
- (Mouse L-cell) (1)
- (Rat brain membrane) (1)
- (Rat liver) (1)
- (Salmonella) (1)
- 1H-NMR-Spectroscopy (1)
- 2 (1)
- 2',7'-dichlorofluorescin (1)
- 2-Acetylaminofluorene (1)
- 2-Dichloroethane (1)
- 2-Dioxetane (1)
- 2-Generation reproduction (1)
- 2-acetylaminofluorene (1)
- 3 (1)
- 3-pentafluoropropene (1)
- 3-tetrafluoropropene (1)
- 3R (1)
- 4'-hydroxylation (1)
- 4-(p-nitrobenzyl)pyridine (1)
- 6-benzylaminopurine (1)
- 7,8-dihydroxyflavone (7,8-DHF) (1)
- 8-Hydroxy-deoxyguanosine (1)
- A(2B) receptors (1)
- A1 (1)
- A1 Adenosine receptors (1)
- A2B adenosine receptor (1)
- A2BAR (1)
- A<sub>2</sub> Adenosine receptor (1)
- AMPK (1)
- API-Massenspektrometrie (1)
- AUM (1)
- A\(_{2A}\) adenosine receptor antagonist (1)
- Acetylcysteinderivate (1)
- Acrylamid (1)
- Acrylamide (1)
- Actin (1)
- Actin cytoskeleton (1)
- Adenosine receptor (1)
- Adenosine receptor antagonists (1)
- Adrenergic receptor (1)
- Adverse outcome pathway (AOP) (1)
- Aflatoxin (1)
- Aflatoxin B1 (1)
- Aldosteronantagonist (1)
- Alkylation (1)
- Alzheimers disease (1)
- Amino acid composition (1)
- Amino acids (1)
- Aminosäuren (1)
- Anabolieagent (1)
- Angiotensin-II-Blocker (1)
- Angst (1)
- Aniline derivatives (1)
- Animal model (1)
- Anthocyane (1)
- Anthraquinone glycosides (1)
- Antibodies (1)
- Antikörper (1)
- Anxiety (1)
- Apoptose (1)
- Apoptosis (1)
- Aryl hydrocarbon rnonooxygenase (1)
- Astrozyt (1)
- Atria (1)
- Aufmerksamkeits-Defizit-Syndrom (1)
- Autofocus (1)
- Azole (1)
- Azoles (1)
- B cells (1)
- BETA(2)-adrenergic receptor (1)
- BRET (1)
- Background DNA damage (1)
- Bacterial Toxins (1)
- Bacterial meningitis (1)
- Bakterielle Hirnhautentzündung (1)
- Bakterien (1)
- Barbiturat (1)
- Barbiturates (1)
- Barth syndrome (1)
- Bcl-2 (1)
- Benfotiamin (1)
- Benzefuran dioxetane (1)
- Benzefuran epoxide (1)
- Benzo(a)pyrene-DNA binding (1)
- Berenil (1)
- Beta(1)-adrenergic receptor (1)
- Beta(2)-adrenergic receptor (1)
- Beta-1-Rezeptor (1)
- Beta-1-receptor (1)
- Beta-Adrenergic Receptor (1)
- Beta-Adrenozeptor (1)
- Bioluminescence resonance energy transfer (1)
- Biomarker (1)
- Biomarkers (1)
- Biosensor (1)
- Bisphenol A (1)
- Bromodeoxyuridine labeling (1)
- Brustkrebs (1)
- C1q/TNF related protein (CTRP) (1)
- CAMP production (1)
- CFC replacements (1)
- CIB1 (1)
- CRISPR Cas9 (1)
- CRISPR/Cas9 (1)
- CXCR4 (1)
- CYP19 (1)
- CYP51 (1)
- CaMKII (1)
- Calcium (1)
- Cancer prevention (1)
- Carcinogen risk Individual susceptibili (1)
- Carcinogenic potency (1)
- Cardiac myocyte ; Beta-Receptor ; Muscarinic receptor ; cAMP ; G-protein ; Serum (1)
- Cardiomyocyte (1)
- Cell adhesion (1)
- Cell death and comet assay (1)
- Cell transformation (1)
- Chemical carcinogenesis (1)
- Chemokine (1)
- Chemokine receptors (1)
- Chemotactic receptors (1)
- Chlorfluorkohlenstoffe (1)
- Choline deficiency (1)
- Cholinesteraseinhibitor (1)
- Chromosome aberration (1)
- Chromosome distribution (1)
- Chronic heart-failure (1)
- Clonidin (1)
- Colon cancer (1)
- Comet Assay (1)
- Comet assay (1)
- Covalent DNA binding (1)
- Covalent binding (1)
- Covalent binding index (1)
- Covalent binding index - Diethylstilbestrol (1)
- Cyclic AMP (1)
- Cyclo-AMP (1)
- Cyclo-GMP (1)
- Cytochrom P450 (1)
- Cytochrome b5 (1)
- Cytologie (1)
- DAMGO (1)
- DCM genetic background (1)
- DES (1)
- DNA Damage (1)
- DNA adduct . Repair endonuclease (1)
- DNA adducts (1)
- DNA binching (1)
- DNA damage response (1)
- DNA metabolism (1)
- DNA methylation (1)
- DNA transfection (1)
- DNA-Addukte (1)
- DNS-Bindung (1)
- DNS-Strangbruch (1)
- Depression (1)
- Dermatologie (1)
- Di (1)
- Dietary process-related contaminants (1)
- Diisononyl phthalate (1)
- Dilated cardiomyopathy (1)
- Dioscorea (1)
- Dose response relationships (1)
- Dosis-Wirkungs-Beziehung (1)
- Drug resistance (1)
- Dualstere Liganden (1)
- Dualsteric Ligands (1)
- ERK signaling (1)
- ERK-Kaskade (1)
- ERK-cascade (1)
- Electric Field (1)
- Electrical breakdown (1)
- Electrophiles (1)
- Elektrofusion (1)
- Elektroporation (1)
- Emodin (1)
- Endogenous genotoxicity (1)
- Entzündung (1)
- Epoxide hydrolase (1)
- Erk1/2 (1)
- Ersatzstoff (1)
- Estrone (1)
- Ethionine (1)
- Eukaryotic cell (1)
- Excitotoxicity (1)
- External exposure assessment (1)
- Extrakorporale Dialyse (1)
- FCKW-Ersatzstoffe (1)
- FPG protein (1)
- FRET sensors (1)
- Fabry Disease (FD) (1)
- Fischer 344 rats (1)
- Flow cytometry (1)
- Fluorescence (1)
- Fluorescence Correlation Spectroscopy (1)
- Fluorescence Microscopy (1)
- Fluorescence resonance energy transfer (1)
- Fluorescence-resonance-energy-transfer (1)
- Fluoreszenz (1)
- Fluoreszenzkorrelationsspektroskopie (1)
- Fluoreszenzmikroskopie (1)
- Fluorkohlenwasserstoffe (1)
- Fluoxetin (1)
- Fluoxetine (1)
- Friedreich’s ataxia (1)
- Fumonisin B1 (1)
- Fumonisine (1)
- Fungizid (1)
- Furan (1)
- Förster Resonance Energy Transfer (1)
- G Protein-Coupled Receptor (1)
- G protein coupled receptor (1)
- G protein coupled receptor (GPCR) (1)
- G protein-coupled receptor (1)
- G protein-coupled receptor kinase (1)
- G-protein coupled receptor (1)
- G-protein-coupled receptors (1)
- GABA-receptor complex (1)
- GC-MS (1)
- GC/MS (1)
- GPCR dimerisation (1)
- GPCR signaling (1)
- GPCRs (1)
- GTP-bindende Proteine (1)
- Gastric carcinogenesis (1)
- Gb3 and lyso-Gb3 biomarkers (1)
- Gene Transfer (1)
- Gene transfer (1)
- Genetic instability (1)
- Genomschaden (1)
- Genotyp (1)
- Gentoxikologie (1)
- Glutathion S-Konjugat (1)
- Glutathione Stransferase (1)
- Guanin Nukleotid Austauschfaktor (1)
- Guaninnucleotid-Austauschfaktoren (1)
- Guanylatcyclase (1)
- HCN channel (1)
- HCN-Kanal (1)
- HFC245fa (1)
- HIV (1)
- HIV infection (1)
- HPLC-MS/MS method (1)
- HeLa cells (1)
- Heart failure (1)
- Hemmung der Proliferation schnell wachsender Krebszellen (1)
- Herpesviren (1)
- High-thropughput screening (1)
- High-throughput screening (1)
- Hintergrund-DNA-Schaden (1)
- Hochdurchsatz-Screening (1)
- Hoechst 33258 dye (1)
- Homocystein (1)
- Hsp90 (1)
- Human platelets (1)
- Hybridoma (1)
- Häm (1)
- I1 Imidazolin Bindungsstelle (1)
- I1 imidazoline binding site (1)
- Immunization (1)
- Immunologie (1)
- In vitro testing (1)
- In vitro toxicity testing (1)
- In vivo (1)
- In-silico Modell (1)
- Inflammation (1)
- Inhibition (1)
- Ischemia/reperfusion (1)
- K + -channels (1)
- Kanzerogenese (1)
- Kardiomyozyt (1)
- Kidneys (1)
- Kinetochore (1)
- Kinetochores (1)
- Knockout (1)
- Kongestive Herzmuskelkrankheit (1)
- Krebs (1)
- Krebs <Medizin> (1)
- L5178Y cells (1)
- LC-MS (1)
- LC-MS/MS (1)
- LTB4 receptor (1)
- Latrophilin (1)
- Leukocyte/endothelium interaction (1)
- Ligand <Biochemie> (1)
- Lung (1)
- MAP-Kinase (1)
- MMQ cells (1)
- Magenkrebs (1)
- MammaJian mutagenicity test (1)
- Massenspektrometrie (1)
- Mastzelle (1)
- Maus (1)
- Mechanism of action (1)
- Melanocortin 4 receptor (MC4R) (1)
- Melanocyte stimulating hormones MSH (1)
- Merkaptolaktat (1)
- Merkaptursäure (1)
- Merkaptursäuren (1)
- Metabolic activation (1)
- Metabolism (1)
- Metabolism saturation (1)
- Metabolismus (1)
- Metabonomics (1)
- Metabonomix (1)
- Methylphenidat (1)
- Microcirculation (1)
- Micronucleus formation (1)
- Micronucleus test (1)
- Microscopy (1)
- Mikrokerne (1)
- Mitosis (1)
- Molekularpharmakologie (1)
- Multivariate Analyse (1)
- Mutagenicity (1)
- Mutagenicity assay (1)
- Mutagenitätstest (1)
- Mutagens (1)
- Mutation assay (1)
- Mykotoxin (1)
- N-methyl-N-nitrosourea (1)
- N1E 115 cells (1)
- NADPH-Oxidase (1)
- Na\(_V\)1.8 (1)
- Neomycin Resistance (1)
- Nephrotoxicity (1)
- Nephrotoxizität (1)
- Nervennetz (1)
- Nervenzelle (1)
- Nitrosation (1)
- Nitrosativer Stress (1)
- Nitrosierung (1)
- OXPHOS (1)
- Oxidative Stress (1)
- Oxidative stress (1)
- Oxygen radical (1)
- PBPK/PBTK model (1)
- PDE (1)
- PDE2 (1)
- PDXP inhibitors (1)
- PKA (1)
- PTH1R (1)
- Parathormon (1)
- Partial Agonists (1)
- Partialagonismus (1)
- Patulin (1)
- Peptides (1)
- Perforine (1)
- PhD thesis pharmacology (1)
- Pharmakogenetik (1)
- Phosphatase (1)
- Phosphatasen (1)
- Phosphodiesterase (1)
- Phosphoglykolat-Phosphatase (1)
- Phosphoglykolatphosphatase (1)
- Photoaffinity labelling (1)
- Physiologically based kinetic models (1)
- Physiologie (1)
- Phänotyp (1)
- Pointmutation (1)
- Pore (1)
- Pore formation (1)
- Pore-formation (1)
- Porenbildung (1)
- Prevalence (1)
- Prognostic impact (1)
- Prolactin (1)
- Propenderivate (1)
- Protein binding (1)
- Protein coding (1)
- Proteinaddukte (1)
- Proteinbindung (1)
- Proteintyrosinphosphatase (1)
- Protonen-NMR-Spektroskopie (1)
- Quantitative risk assessment (1)
- RAMP (1)
- RBM20 mutations (1)
- ROS (1)
- Radiation inactivation (1)
- Radicals (1)
- Radioligand binding - 86Rb + -efflux (1)
- Radioligands (1)
- Radioligauds (1)
- Raf kinase inhibitor protein (1)
- Raman micro-spectroscopy (1)
- Rat Iiver microsomes (1)
- Rat liver peroxisome (1)
- Ratte (1)
- Reactive intermediates (1)
- Reaktive Zwischenstufe (1)
- Receptor (1)
- Receptor dynamics (1)
- Regulation (1)
- Regulator of G protein signaling 2 (1)
- Renin-Angiotensin-System (1)
- Resveratrol (1)
- Rgs2 (1)
- Riot control agents (1)
- Risikoanalyse (1)
- Risikobewertung (1)
- Risk assessment (1)
- Risk estimation (1)
- Risk-factors (1)
- SCN5a (1)
- ST-elevation myocardial infarction (1)
- Salmonella typhimurium (1)
- Sensitivity (1)
- Sensor (1)
- Short-term tests (1)
- Signal transduction (1)
- Species Differences (1)
- Species differences (1)
- Spermatogenesis (1)
- Speziesunterschiede (1)
- Spontaneous tumours (1)
- Src (1)
- Stable Transformation (1)
- Statin (1)
- Stickstoffoxidsynthase (1)
- Streptococcus pneumoniae (1)
- Streptomyces (1)
- Stress (1)
- Structureactivity relationship (1)
- Styrol (1)
- Systembiologie (1)
- T cells (1)
- TK6 cells (1)
- Target size (1)
- Theophylline (1)
- Thymidine glycol (1)
- Tiermodell (1)
- Toxicokinetics (1)
- Toxikokinetik (1)
- Toxizität (1)
- Toxizitätstest (1)
- Transfection (1)
- Transgenic mouse (1)
- Transgenie mice (1)
- Transkriptionsfaktoren (1)
- Trenbolone (1)
- Trifluorpropionsäure (1)
- Tumorzelle (1)
- Tyrosin (1)
- Tyrosin phosphatase (1)
- Unscheduled DNA synthesis (1)
- Urämische Toxine (1)
- Uterine tumors (1)
- Valvular heart-desease (1)
- Venerologie (1)
- Volume distribution (1)
- Wachstumskonus (1)
- Water resources (1)
- Xanthines (1)
- Zell-Adhäsion (1)
- Zelladhäsion (1)
- Zelle (1)
- Zellkultur (1)
- Zellskelett (1)
- Zellteilung (1)
- Zelltransport (1)
- [3H]PIA binding (1)
- absorption (1)
- activation (1)
- active zone (1)
- acute slices (1)
- adduct (1)
- adenine (1)
- adenosine (1)
- adenosine 3',5'-cyclic monophosphate (1)
- adenylate cyclase (1)
- adenylyl cyclase signaling cascade (1)
- adenylyl-cyclase isoforms (1)
- adhesion GPCR (1)
- adiponectin (1)
- adipose tissue (1)
- adrenerge Rezeptoren (1)
- adrenergic receptors (1)
- adult cardiac myocytes (1)
- adverse outcome pathway (1)
- adverse outcome pathway (AOP) (1)
- aflatoxin (1)
- aflatoxin B1 (1)
- ageing (1)
- agonists (1)
- alkylation (1)
- allelic variant (1)
- alpha2-KO Maus (1)
- alpha2-KO mouse (1)
- alpha2-Rezeptor (1)
- alpha2-receptor (1)
- alternative methods (1)
- amine (1)
- amino acid (1)
- antagonists (1)
- anthocyanins (1)
- anti-Parkinson agents (1)
- anti-inflammatory agents (1)
- antibacterial/antiviral drug (1)
- antibodies (1)
- antibody/autoantibody (1)
- antioxidants (1)
- aortocaval fistula model (1)
- aromatic amides (1)
- arrhythmia (1)
- arrhythmogenesis (1)
- assay (1)
- association (1)
- astrocytes (1)
- atopic eczema (1)
- atrial natriuretic peptide (1)
- avaliação de risco (1)
- bacterial meningitis (1)
- bariatric surgery (1)
- base excision repair (incision activity) (1)
- beta2-adrenoceptor knockout (1)
- beta3 CL 316,243 (1)
- binding affinity (1)
- bioactive compounds (1)
- biofilms (1)
- biological techniques (1)
- biology (1)
- biomarker (1)
- biomarker of exposure (1)
- biomarkers (1)
- biotransformation (1)
- bisphenol a (1)
- blood coagulation factor XIII (1)
- blood plasma (1)
- blood pressure (1)
- blood samples (1)
- bone marrow (1)
- brain damage (1)
- brain membranes (1)
- calcitonin gene-related peptide (1)
- calmodulin (1)
- cancer (1)
- cardiac magnetic resonance imaging (1)
- cardiac myocyte ; muscarinic K current ; G-protein ; Albumin ; serum (1)
- cardiac remodelling (1)
- cardiomyocyte (1)
- cardiomyocytes (1)
- cardiovascular diseases (1)
- caveolin-1 (1)
- cell adhesion (1)
- cell culture (1)
- cell fate (1)
- cell fusion (1)
- cell proliferation (1)
- cell signalling (1)
- cell staining (1)
- cellular-trafficking (1)
- chalcone (1)
- chemotactic receptors (1)
- chemotaxis (1)
- child health (1)
- cholesterol depletion (1)
- cholesterol-dependent cytolysin (1)
- cholinesterase (1)
- cholinesterase inhibitors (1)
- chronic heart failure (1)
- chronic kidney disease (1)
- chronophin (1)
- cisplatin (1)
- classification (1)
- classification and labeling (1)
- clonidine (1)
- co-culture (1)
- coated vesicles (1)
- cognitive impairment (1)
- coherent anti-Stokes Raman scattering (CARS) microscopy (1)
- compartments (1)
- conduction disease (1)
- conformational auto-epitope (1)
- conjugated mycotoxins (1)
- constitutive activity (1)
- contact lens (1)
- continuous (1)
- contractility (1)
- coumarin (1)
- coupled (1)
- coupled receptor (1)
- covalent (1)
- covalent binding (1)
- creatinine (1)
- crystal structure (1)
- cyclic AMP (1)
- cyclic dipeptide (1)
- cyclic nucleotides such as cyclic adenosine monophosphate (1)
- cyclic peptides/cyclopeptides (1)
- cyclic-AMP (1)
- cyclic-gmp (1)
- cyclopeptide therapy (1)
- cytochrome P450 2C9 (1)
- cytochrome P450s (1)
- cytochrome p450 (1)
- cytogenetic effects (1)
- cytome biomarkers (1)
- cytosol (1)
- cytotoxic (1)
- dCIRL (1)
- danio rerio (1)
- definition (1)
- dendritic spines (1)
- desensitization (1)
- detrusor muscle (1)
- developmental biology (1)
- diabetes (1)
- diagnosis (1)
- dicyclohexyl phthalate (1)
- diet (1)
- dilated cardiomyopathy with ataxia (1)
- disrupting chemicals (1)
- disruptor endócrino (1)
- docking (1)
- domains (1)
- dormancy (1)
- dose (1)
- down-regulation (1)
- drug (1)
- dualsteric ligands (1)
- dunce (1)
- eccentric hypertrophy (1)
- ectodomain cleavage (1)
- efficient intervention points (1)
- endocrine disruptor (1)
- endogenous (1)
- energy-transfer (1)
- environmental phenols (1)
- enzyme-linked immunoassays (1)
- estrogen receptor (1)
- ethanol (1)
- etoposide (1)
- etox database (1)
- eugenol (1)
- exposição humana (1)
- exposure (1)
- extrapolation (1)
- fatty liver (1)
- fentanyl (1)
- fetal testis (1)
- fluorescence correlation spectroscopy (1)
- fluorescence detection (1)
- fluorescence imaging (1)
- fluorescence recovery after photobleaching (1)
- fluorescent probes (1)
- fluorocarbons (1)
- food contact materials (1)
- food safety (1)
- food security (1)
- formyl peptides (1)
- fumonisin B1 (1)
- functional clustering (1)
- fungi (1)
- furan (1)
- gastrointestinal cancer (1)
- general medicine (1)
- genetics (1)
- genotoxic (1)
- genotypes (1)
- genotyping (1)
- glucuronide (1)
- glutamate (1)
- glutathion S-conjugate (1)
- glycolytic flux control (1)
- gprotein (1)
- gravidez (1)
- growth cone (1)
- guanine nucleotide exchange factor (1)
- hA<sub>3</sub>AR (1)
- hOCT1 (1)
- haematopoietic stem cells (1)
- halo olefines (1)
- haloacid dehalogenase (1)
- healing and remodelling processes (1)
- heme (1)
- heterogeneous population (1)
- hiPSC-CM (1)
- hidden mycotoxins (1)
- histamine release (1)
- homeostasis (1)
- homocysteine (1)
- homodimerization (1)
- hormone receptors (1)
- human (1)
- human A(3) (1)
- human biomonitoring (1)
- human exposure (1)
- human lung (1)
- hydrofluorocarbons (1)
- hypertension (1)
- hypertonic solution (1)
- identification (1)
- impact pharmacogenetics (1)
- in vitro (1)
- in vivo (1)
- in-silico model (1)
- individual (1)
- indolylpyrimidylpiperazines (1)
- induced pluripotent stem cell cardiomyocytes (1)
- induced pluripotent stem cells (1)
- induzierte Phosphatasen MKP-1 und MKP-2 (1)
- inflammatory diseases (1)
- inhalation (1)
- inhibitors (1)
- insulin signaling (1)
- internalization (1)
- international union (1)
- intracellular calcium release (1)
- intracellular loop (1)
- intrinsic metabolism (1)
- ionic look (1)
- ischemic stroke (1)
- isoproterenol (1)
- key event relationship (1)
- kidney (1)
- kinases (1)
- laminopathy (1)
- lamivudine (1)
- late Na\(^+\) current (I\(_{NaL}\)) (1)
- legislation (1)
- life (1)
- ligand binding (1)
- lipid rafts (1)
- lipidomics (1)
- listeriolysin O (1)
- live imaging (1)
- liver microsomes (1)
- living vells (1)
- long-read sequencing (1)
- lovastatin (1)
- lysosomal disruption (1)
- lysosomal storage disorders (1)
- lösliche Guanylylcyclase (1)
- mTOR-inhibitor RAD-001 (1)
- maintenance of genomic integrity (1)
- male rats (1)
- mammalian genomics (1)
- marine sponges (1)
- masked mycotoxins (1)
- mass spectrometry (1)
- matrix metalloproteinase (1)
- maturation strategies (1)
- mechanotransduction (1)
- membrane (1)
- membrane transporters (1)
- memory B cells (1)
- mercaptolactic acid (1)
- mercapturic acids (1)
- metabolites (1)
- metabonomics (1)
- metabotropic signalling (1)
- micronucleus assay (1)
- micronucleus test (1)
- microvessel permeability (1)
- mild (1)
- mitochondria (1)
- mitochondrial DNA polymerase γ (1)
- mitochondrial cardiomyopathy (1)
- mitotic disturbance (1)
- modelo PBPK/PBTK (1)
- modified mycotoxins (1)
- molecular biology (1)
- molecular dynamics (1)
- molecular modeling (1)
- molecular modelling (1)
- monogenetic cardiomyopathies (1)
- mortality (1)
- mouse lymphoma L5178Y (1)
- mouse models DNA damage (1)
- mucosa (1)
- multivariate analysis (1)
- multivariate data analysis (1)
- muscarinic acetylcholine receptor (1)
- mutagen (1)
- mutant mice (1)
- mutation triggers (1)
- mycotoxin derivates (1)
- mycotoxin metabolites (1)
- mycotoxins (1)
- n-hexyl phthalate (1)
- nanopore (1)
- natural (1)
- neocortex (1)
- neurodegenerative diseases (1)
- neuronal dendrites (1)
- neurons (1)
- neutrophils (1)
- nitric-oxide (1)
- nitrosation (1)
- nitrosative stress (1)
- nitroso compound (1)
- no (1)
- nutritional composition (1)
- o-Chlorobenzylidene malononitrile (1)
- obesity (1)
- occurrence (1)
- ochratoxin A (1)
- octopamine (1)
- oligomerization (1)
- opioid ligands (1)
- opioid receptor (1)
- optimal drug combination (1)
- optimal drug targeting (1)
- optimal pharmacological modulation (1)
- optimal treatment strategies (1)
- organ toxicity (1)
- oxidativer Stress (1)
- p53 (1)
- parathyroid hormone (1)
- parathyroid hormone 1 receptor (1)
- partial agonists (1)
- performance liquid-chromatography (1)
- peripheral nerve (1)
- peripheral-blood lymphocytes (1)
- personalized treatment (1)
- perspectives (1)
- pharmacology (1)
- phenotyping (1)
- phosphoglycolate phosphatase (1)
- phosphoinositides (1)
- photoaffinity labelling (1)
- plasma membrane (1)
- poly(ADP-ribosyl)ation (1)
- pore formation (1)
- pore-forming toxin (1)
- potent (1)
- pregnancy (1)
- primary aromatic amine (1)
- protein (1)
- protein adducts (1)
- protein alkylation (1)
- protein design (1)
- protein-coupled receptors (1)
- protein-coupled-receptors (1)
- psoriasis (1)
- purine derivatives (1)
- pyridoxal phosphatase (1)
- pyridoxal phosphatase (PDXP) (1)
- pyrrolizidine alkaloids (1)
- quantitative assessments (1)
- radiation (1)
- radii (1)
- radioligand (1)
- radioligand binding (1)
- rat pheochromocytoma cells (1)
- rats (1)
- reactive metabolites (1)
- reaktive Metabolite (1)
- receptor binding (1)
- receptor pharmacology (1)
- receptor solubilization (1)
- receptor-G protein coupling (1)
- receptor-G protein coupling. (1)
- reduction of ERK1/2 phosphorylation (1)
- reduction of cells proliferation (1)
- regulation (1)
- relaxation (1)
- renal toxicity (1)
- repeated dose (1)
- reproductive and developmental toxicity (1)
- risk (1)
- risk-assesment (1)
- sensor (1)
- sensory physiology (1)
- serum (1)
- sex (1)
- sexual development (1)
- signaling microdomain (1)
- simulated digestion (1)
- single-molecule imaging (1)
- single-molecule microscopy (1)
- solid-phase extraction (1)
- solubilization (1)
- soluble guanylyl cyclase (1)
- sponges (1)
- spontaneously hypersensitive-rats (1)
- staphilococci (1)
- statins (1)
- stomach (1)
- streptomyces (1)
- sub-Saharan Africa (1)
- subtypes (1)
- sugars (1)
- susceptibility (1)
- synapses (1)
- synaptic plasticity (1)
- tMCAO (1)
- tandem mass-spectrometry (1)
- targets (1)
- testosterone production (1)
- tetrafluoropropene (1)
- therapeutic potential (1)
- thyroid hormone (1)
- tissue (1)
- tolbutamide substrate (1)
- toxicity testing (1)
- toxicocinética (1)
- toxicokinetics (1)
- toxicology (1)
- trans-1 (1)
- trans-Golgi network (1)
- transgenic animals (1)
- triazolotriazine derivatives (1)
- trifluoropropionic acid (1)
- tuber (1)
- tumour (1)
- tyrosine phosphatase (1)
- ultrastructure (1)
- urea (1)
- variocosities (1)
- vav2 (1)
- vitamin-D-receptor (1)
- volume overload (1)
- warfarin polymorphisms (1)
- weight of evidence (1)
- yellow fluorescent protein (1)
- µ-Opioid receptor (1)
- β-adrenergic receptors (1)
- β1-adrenoceptor/β1-adrenergic receptor (1)
- βAR (1)
Institute
- Institut für Pharmakologie und Toxikologie (293) (remove)
Sonstige beteiligte Institutionen
- Johns Hopkins School of Medicine (1)
- Johns Hopkins School of Medicine, Baltimore, MD, U.S. (1)
- Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V. (1)
- Max Delbrück Center for Molecular Medicine (1)
- Max-Delbrück-Center für molekulare Medizin, Berlin (1)
- Pharmakologie, Universität Bonn (1)
- Pharmazie, Universität Mailand (1)
In the search for more selective A2-receptor agonists and on the basis that appropriate substitution at C2 is known to impart selectivity for A\(_2\) receptors, 2-alkynyladenosines 2a-d were resynthesized and evaluated in radioligand binding, adenylate cycla.se, and platelet aggregation studies. Binding of [\(^3\)H]NECA to A\(_2\) receptors of rat striatal membranes was inhibited by compounds 2a-d with K\(_i\) values ranging from 2.8 to 16.4 nM. 2-Alkynyladenosines also exhibited high-affmity binding at solubilized A\(_2\) receptors from human platelet membranes. Competition of 2-alkynyladenosines 2a-d for the antagonist radioligand [\(^3\)H]DPCPX and for the agonist [\(^3\)H]CCPA gave K\(_i\) values in the nanomolar range, and the compounds showed moderate A\(_2\) selectivity. In order to improve this selectivity, the correaponding 2-alkynyl derivatives of adenosine-5'-N-ethyluronamide 8a-d were synthesized and tested. A\(_1\) expected, the 5'-N-ethyluronamide derivatives retained the A\(_2\) affinity whereas the A\(_1\) affinity was attenuated, resulting in an up to 10-fold increase in A\(_2\) selectivity. A similar patternwas observed in adenylate cyclase assays andin platelet aggregation studies. A 30- to 45-fold selectivity for platelet A\(_2\) receptors compared to A\(_1\) receptors was found for compounds 8a-c in adenylate cyclase studies.
Photoaffinity-labeled N-formyl chemotactic peptide receptors from human neutrophils solubilized in octyl glucoside exhibit two forms upon sucrose density gradient sedimentation, with apparent Sedimentation coefficients of approximately 4 and 7 S. Tbe 7 S form can be converted to the 4 S form by guanosine 5' -0- (3-thiotriphosphate) (GTP-yS) with an EC&o of -20 nM, suggesting that the 7 S form may represent a physical complex of the receptor with endogenous G protein (Jesaitis, A. J., Tolley, J. 0., Bokoch, G. M., and Allen, R. A. (1989) J. Cell Biol. 109, 2783-2790). To probe the nature of the 7 S form, we reconstituted the 7 S form from the 4 S form by adding purified G protein. The 4 S form, obtained by solubilizing GTP-yS-treated neutrophil plasma membranes, was incubated with purified (>95%) G. protein from bovine brain (containing both G\(_{ia1}\) and G\(_{ia2}\)) or with neutrophil G protein (G\(_a\)), and formation of the 7 S complex was analyzed on sucrose density gradients. The EC\(_{50}\) of 7 S complex formation induced by the two G proteins was 70 \(\pm\) 25 and 170 \(\pm\) 40 DM for G\(_a\) and G\(_1\), respectively. No complexation was measurable when bovine transducin (G\(_t\)) was used up to 30 times the EC\(_{50\) for G\(_a\). The EC\(_{50}\) for G\(_t\) was the same for receptors, obtained from formyl peptide-stimulated or unstimulated cells. The addition of 10 \(\mu\)M GTP-yS to the reconstituted 7 S complex caused a complete reversion of the receptor to the 4 S form, and anti-G\(_1\) peptide antisera immunosedimented the 7 S form. ADP-ribosylation of Gt prevented formation of the 7 S form even at 20 times the concentration of unribosylated G. normally used to attain 50% conversion to the 7 S form. These observations suggest that the 7 S species is a pbysical complex containing N-formyl chemotactic peptide receptor and G protein.
The mechanism of the therapeutic and prophylactic effects of carbamazepine (CBZ) in affective psychoses is unknown but may in part be related to the potent competitive interaction of CBZ with adenosine-binding sites in the brain. The antioonvulsant and sedative properties of CBZ are reminiscent of the effects evoked by adenosine-agonists and contrast sharply with the opposite aclions of adenosine-antagonists like caffeine. However. indirect evidence suggests an antagonist- rather than an agonist-like activity of CBZ at adenosi11e-receptors. We have used various model systems, in which adenosine receptor subtypes mediate different second messenger-responses, to investigate this apparent paradox. CBZ was found to antagonize the A\(_1\) receptor-mediated inhibition of cydic AMP accumulation in cultured astroblasts and in GH3-cells. Furthermore, CBZ also inhibits the adenosine-induced increase in the level of cyclic AMP in cultured astroblasts, which is mediated by low-affinity A\(_{2b}\)-receptors. ln contrast, CBZ does not block the inhibition elicited by adenosine-agonists of the agonist-induced increased formation of inositolphosphates in human neutrophils, which is mediated by high-affinity A\(_{2a}\)-receptors. The specific antagonism by CBZ of A\(_1\)- but not of high-affinity A\(_{2a}\)-receptors was further supported by binding experiments using rat brain membranes. These results suggest tbat the paradox of CBZ's antagonistic effects at adenosine-receptors might be at least partially reconciled by a selective antagonistic action of CBZ at A\(_1\)recertors but not at high-affinity A\(_{2a}\)-receptors.
Radioligand binding to A\(_1\) adenosine receptors at brain membranes from seven species was investigated. The antagonist 8-cyclopentyl-1 ,3-[\(^3\)H]dipropylxanthine ([\(^3\)H]DPCPX) bound with affinities between 0.17 nM in sheep brain and 2.1 nM in guinea pig brain. Competition of several antagonists for [\(^3\)H]DPCPX binding showed that the most potent compounds were DPCPX with K\(_i\) values of 0.05 nM in bovine brain and 1.1 nM in guinea pig brain and xanthine amine congener (XAC) with K\(_i\) values of 0.03 nM in bovine brain and 5.5 nM in guinea pig brain. The differences in affinity of the agonist radio Iigand 2-chloro-N\(^6\) -[\(^3\)H]cyclopen tyladenosine ([\(^3\)H]CCP A) were less pronounced, rauging from a K\(_D\) value of 0.12 nM (hamster brain) to 0.42 nM (guinea pig brain). Agonist competition for [\(^3\)H]DPCPX binding of photoaffinity labelling, however, exhibited marked species differences. N-Ethylcarboxamidoadenosine (NECA) and S-N\(^6\)-phenylisopropyladenosine (S-PIA) showed 20 to 25-fold different K\(_D\) values in different species. NECA had a particularly high affinity in guinea pig brain and was only two-fold less potent than R-PIA. Thus, the difference from the "classical" A\(_1\) receptor profile (R-PIA > -NECA > S-PIA) is not sufficient to speculate that A\(_1\) receptor subtypes may exist that are coupled to different effector systems. Our data show that these difference can easily be explained by species differences.
Active neuropeptide Y receptors were solubilized from rabbit kidney membranes using the zwitterionic detergent 3-[ (3-cholamidopropy l)dimethylammonio ]- 1-propanesulfonic acid (CHAPS). In membrane fragmentsandsoluble extracts neuropeptide Y bindingwas time dependent, saturable, reversible, and of high affinity. Scatchard analysis of equilibrium binding data indicated a single class of binding sites with respective Kn and Bmax values of 0.09 nM and 530 fmol/mg of protein for the membrane-bound receptors and 0.10 nM and 1585 fmol/mg of protein for the soluble receptors. Neuropeptide Y bindingwas specifically inhibited by the nonhydrolyzable GTP analog guanosine 5' -0- (3-thiotripbosphate) in a concentration-dependent manner, with IC\(_{50}\) values of 28 and 0.14 \(\mu\)M for membrane- bound and soluble receptors, respectively, suggesting that neuropeptide Y receptors are functionally coupled to GTP-binding regulatory proteins. CrossHoking studies were performed with the heterobifunctional N-hydroxysuccinimidyl-4-azidobenzoate and the monofunctional neuropeptide Y derivative, azidobenzoyl and led to the identification of a 100 kDa peptide that should represent the covalently labeled neuropeptide Y receptor.
The effects of guanine nucleotides on binding of 8-cyclopentyl-1,3-[\(^3\)H]dipropylxanthine [\(^3\)H]DPCPX), a highly selective A\(_1\) adenosine receptor antagonist, have been investigated in rat brain membranes and solubilized A\(_1\) receptors. GTP, which induces uncoupling of receptors from guanine nucleotide binding proteins, increased binding of [\(^3\)H]DPCPX in a concentration-dependent manner. The rank order of potency for different guanine nucleotides for increasing [\(^3\)H]DPCPX bindingwas the same as for guanine nuc1eotide-induced inhibition of agonist binding. Therefore, a role for a guanine nucleotide binding protein, e.g., G\(_i\), in the regulation of antagonist binding is suggested. This was confirmed by inactivation ofGi by N-ethylmaleimide (NEM) treatment of membranes, which resulted in an increase in [\(^3\)H]DPCPX binding similar to that seen with addition of GTP. Kinetic and equilibrium binding studies showed that the GTP- or NEM-induced increase in antagonist binding was not caused by an affinity change of A\(-1\) receptors for [\(^3\)H]DPCPX but by an increased Bmu value. Guanine nucleotides had similar effects on membrane-bound and solubilized receptors, with the effects in the solubilized system being more pronounced. In the absence of GTP, when rnost receptors are in a high-affinity state for agonists, only a few receptors are labeled by [\(^3\)H]DPCPX. It is suggested that [\(^3\)H]DPCPX binding is inhibited when receptors are coupled to G\(_i\). Therefore, uncoupling of A\(_1\) receptors from G\(_i\) by guanine nucleotides or by inactivation of G\(_i\) with NEM results in an increased antagonist binding.
Key Words: Adenosine receptors-8 -Cyclopentyl-1,3-eH]dipropylxanthine-Antagenist binding-Guanine nucleotide effects. Klotz K.-N. et al. Guanine nucleotide etfects on 8-cyclopentyl-1 ,3-eH]dipropylxanthine binding to membrane-bound and solubilized A1 adenosine receptors of rat brain. J. Neurochem. 54, 1988-1994 (1990).
1 Adenosine and its metabolically stable analogue N.etbyl-carboxamidoadenosine (NECA) enhance histamine release from rat peritoneal mast cells when tbese are stimulated by calciummobilizing agents. NECA and adenosine shift the concentration-response curve of tbe calcium ionophore A23187 to lower concentrations. 2 The potencies of NECA or adenosinein enhancing A23187-induced histamine release are dependent on the Ievel of stimulated release in tbe absence of adenosine analogues. At high Ievels of release their potencies are up to 20 times higher than at low Ievels. Consequently, averaged concentration-response curves of adenosine and NECA for enhancing bistamine release are shallow. 3 The adenosine transport blocker S-(p-nitrobenzyl)-6-thioinosine (NBTI) has no effect by itself at low Ievels of stimulated histamine release, but abolishes the enhancing effect of adenosine. At high Ievels of release, however, NBTI alone enhances the release of histamine. 4 lt is concluded that adenosine and calcium reciprocally enhance the sensitivity of the secretory processes to the effects of the other agent. The Ievels of intracellular adenosine obtained by trapping adenosine inside stimulated mast cells are sufficient to enhance histamine release substantially, suggesting that this effect may play a physiological and pathophysiological role.
In the present work we studied the pharmacological profile of adenosine receptors in guinea pig atria by investigating the effect of different adenosine analogues on 86Rb + -efflux from isolated left atria and on binding of the antagonist radioligand 8-cyclopentyl-1 ,3-[\(^3\)H]dipropylxanthine ([\(^3\)H]DPCPX) to atrial membrane preparations. The rate of \8^{86}\)Rb\(^+\) -effiux was increased twofold by the maximally effective concentrations of adenosine receptor agonists. The EC50-values for 2-chloro-N\(^6\)-cyclopentyladenosine (CCPA), R-N\(^6\)-phenylisopropyladenosine (R-PIA), 5'-Nethylcarboxamidoadenosine (NECA), and S-N\(^6\)-phenylisopropyladenosine (S-PIA) were 0.10, 0.14, 0.24 and 12.9 \(\mu\)M, respectively. DPCPX shifted the R-PIA concentration-response curve to the right in a concentration-dependent manner with a K\(_B\)-value of 8.1 nM, indicating competitive antagonism. [\(^3\)H]DPCPX showed a saturable binding to atrial membranes with a Bmax·value of 227 fmol/mg protein and a K\(_D\)-value of 1.3 nM. Competition experiments showed a similar potency for the three agonists CCPA, R-PIA and NECA. S-PIA is 200 times less potent than R-PIA. Our results suggest that the K\(^+\) channel-coupled adenosine receptor in guinea pig atria is of an A\(_1\) subtype.
The tritiated analogue of 2-chloro-N6-cyclopentyladenosine (CCPA), an adenosine derivative with subnanomolar affinity and a 10000-fold selectivity for A1 adenosine receptors, has been examined as a new agonist radioligand. [3H]CCP A was prepared with a specifi.c radioactivity of 1.58 TBqjmmol ( 43 Ci/mmol) and bound in a reversible manner to A1 receptors from rat brain membranes with a high affinity K0 -value of 0.2 nmol/1. In the presence of GTP a K0 -value of 13 nmol/1 was determined for the low affinity state for agonist binding. Competition of several adenosine receptor agonists and antagonists for [3H]CCPA binding to rat brain membranes confrrmed binding to an A1 receptor. Solubilized A1 receptors bound [3H]CCPA with similar affinity for the high affinity state. At solubilized receptors a reduced association rate was observed in the presence of MgC12, as has been shown for the agonist [ 3H]N6-phenylisopropyladenosine ([3H]PIA). [3H]CCPA was also used for detection of A1 receptors in rat cardio myocyte membranes, a tissue with a very low receptor density. A K0 -value of 0.4 nmol/1 and a Bmax-value of 16 fmol/ mg protein was determined in these membranes. In human platelet membranes no specific binding of [3H]CCPA was measured at concentrations up to 400 nmoljl, indicating that A2 receptors did not bind [3H]CCPA. Based on the subnanomolar affinity and the high selectivity for A1 receptors [ 3H]CCPA proved to be a useful agonist radioligand for characterization of A 1 adenosine receptors also in tissues with very low receptor density.
Radiation inactivation analysis of the binding of the A1 adenosine receptor antagonist, 8-cyclopentyl-1,3-dipropylxanthine to rat brain membranes yielded a radiation inactivation size of 58 kDa. In the presence of GTPyS this was reduced to 33 kDa, in good agreement with the size of the ligand-binding subunit detected after photoaffinity labelling. The data indicate that the structural association of A\(_1\) adenosine receptors with G-protein components is altered in situ in the presence of guanine nucleotides.
Chemical modification of amino acid residues was used to probe the ligand recognition site of A\(_1\) adenosine receptors from rat brain membranes. The effect of treatment with group·specific reagents on agonist and antagonist radioligand binding was investigated. The histidine-specific reagent diethylpyrocarbonate (DEP) induced a loss of binding of the agonist R-N\(^6\)-[\(^3\)H]phenylisopropyladenosine ([\(^3\)H]PIA), which could be prevented in part by agonists, but not by antagonists. DEP treatment induced also a loss of binding of the antagonist [\(^3\)H]8- cyclopentyl-1 ,3-dipropylxanthine ([\(^3\)H]DPCPX). Antagonists protected A\(_1\) receptors from this inactivation while agonists did not. This result provided evidence for the existence of at least 2 different histidine residues involved in ligand binding. Consistent with a modification of the binding site, DEP did not alter the affinity of [\(^3\)H]DPCPX, but reduced receptor number. From the selective protection of [\(^3\)H] PIA and [\(^3\)H]DPCPX binding from inactivation, it is concluded that agonists and antagonists oocupy different domains at the binding site. Sulfhydryl modifying reagents did not influence antagonist binding, but inhibited agonist binding. This effect is explained by modification of tbe inhibitory guanine nucleotide binding protein. Pyridoxal 5-phosphate inactivated both [\(^3\)H]PIA and [\(^3\)H]DPCPX binding, but the receptors could not be protected from inactivation by ligands. Therefore, no amino group seems to be located at the Iigand binding site. In addition, it was shown that no further amino acids witb polar side chains are present. The absence of bydrophilic amino acids frout the recognition site of the receptor apart from histidine suggests an explanation for the lack of hydrophilic ligands with high affinity for A\(_1\) receptors.
Tbe 2',3'-dideoxy analogue of the potent A\(_1\) receptor agonist, N\(^6\)-cyclohexyladenosine (CHA), was synthesized as a potential antagonist for the A\(_1\) adenosine receptor. In sturlies on adenylate cyclase 2',3'-dideoxy-N\(^6\)-cyclohexyladenosine (ddCHA) did not show agonist properties at A\(_1\) or at A\(_2\) receptors. However, it antagonized the inhibition by R-PIA of adenylate cyclase activity of fat cell membranes via A\(_1\) receptors with a K\(_i\) value of 13 \(\mu\)M. ddCHA competed for the binding of the selective A1 receptor antagonist, [\(^3\) HJ8-cyclopentyl-1,3-dipropylxantbine ([\(^3\)H]DPCPX), to rat brain membranes with a K\(_i\) value of 4.8 \(\mu\)M; GTP did not affect the competition curve. In contrast to the marked stereoselectivity of the A\(_1\) receptor for the cx- and the natural ß-anomer of adenosine, the cx-anomer of ddCHA showed a comparable affinity for the A\(_1\) receptor (K\(_i\) value 13.9 \8\mu\)M). These data indicate that the 2'- and 3'-hydroxy groups of adenosine and its derivatives are required foragonist activity at and high affinity binding to A\(_1\) adenosine receptors and for the distinction between the cx- and ß-forms.
2-Chloro-N\(^6\)-cyclopentyladenosine: a highly selective agonist at A\(_1\) adenosine receptors
(1988)
2-Chloro-N\(^6\)-cyclopentyladenosine (CCPA) was synthesized as a potential high affinity ligand for At adenosine receptors. Binding of [\(^3\)H]PIA to A1 receptors of rat brain membranes was inhibited by CCP A with a Ki-value of 0.4 nM, compared to a Ki-value of 0.8 nM for the parent compound N\(^6\)-cyclopentyladenosine (CPA). Binding of [\(^3\)H]NECA to A\(_2\) receptors of rat striatal membranes was inhibited with a Ki-value of 3900 nM, demonstrating an almost 10,000-fold A\(_1\)-selectivity of CCPA. CCP A inhibited the activity of rat fat cell membrane adenylate cyclase, a model for the A\(_1\) receptor, with an IC\(_{50}\)-value of 33 nM, and it stimulated the adenylate cyclase activity of human platelet membranes with an EC\(_{50}\)-value of 3500 nM. The more than 100-fold A\(_1\)-selectivity compares favourably with a 38-fold selectivity of CPA. Thus, CCPA is an agonist at A\(_1\) adenosine receptors with a 4-fold higher selectivity and 2-fold higher affinity than CPA, and a considerably higher selectivity than the standard At receptor agonist R-N\(^6\) -phenylisopropyladenosine (R-PIA). CCP A represents the agonist with the highest selectivity for A\(_1\) receptors reported so far.
Adenosine receptor agonists: Synthesis and biological evaluation of 1-deaza analogues of adenosine
(1988)
In a search for more selective A\(_1\) adenosine receptor agonists, N\(^6\)-[(R)-(-)-1-methyl-2-phenethyl]-1-deazaadenosine (1-deaza-R-PIA, 3a), N\(^6\)-cyclopentyl-1-deazaadenosine (1-deazaCPA, 3b), N\(^6\)-cyclohexyl-l-deazaadenosine (1-deazaCHA, Sc), and the corresponding 2-chloro derivatives 2a-c were synthesized from 5,7-dichloro-3-ß-D-ribofuranosyl-3Himidazo[ 4,5-b]pyridine (1). On the other band, N-ethyl-1'-deoxy-1'-(1-deaza-6-amino-9H-purin-9-yl)-ß-D-ribofuranuronamide (1-deazaNECA, 10) was prepared from 7-nitro-3-ß-D-ribofuranosyl-3H-imidazo[4,5-b]pyridine (4), in an attempt to find a more selective A\(_2\) agonist. The activity of all deaza analogues at adenosine receptors has been determined in adenylate cyclase andin radioligand binding studies. 1-DeazaNECA (10) proved tobe a nonselective agonist at both subtypes of the adenosine receptor. It is about 10-fold less active than NECA but clearly more active than the parent compound 1-deazaadenosine as an inhibitor of platelet aggregation and as a stimulator of cyclic AMP accumulation. The N\(^6\)-substituted 1-deazaadenosines largely retain the A\(_1\) agonist activity of their parent compounds, but lose some of their A\(_2\) agonist activity. This results in A\(_1\)-selective compounds, of which N\(^6\)cyclopentyl- 2-chloro-1-deazaadenosine (1-deaza-2-Cl-CPA, 2b) was identified as the most selective agonist at A\(_1\) adenosine receptors so far known. The activity of all 1-deaza analogues confirms that the presence of the nitrogen atom at position 1 of the purine ring is not critical for A\(_1\) receptor mediated adenosine actions.
Human platelet membranes were solubilized with the zwitterionic detergent CHAPS (3-[3-(cholamidopropyl)dimethylammonio]- 1-propanesulfonate) and the solubilized extract subjected to gel ftltration. Binding of the adenosine receptor agonist [\(^3\)H]NECA (5'-N-ethylcarboxamidoadenosine) was measured to the eluted fractions. Two [\(^3\)H]NECA binding peaks were eluted, the first of them with the void volume. This first peak represented between 10% and 25% of the [\(^3\)H]NECA binding activity eluted from the column. It bound [\(^3\)H]NECA in a reversible, saturable and GTPdependent manner with an affinity of 46 nmol/1 and a binding capacity of 510 fmol/mg protein. Various adenosine receptor ligands competed for the binding of [\(^3\)H]NECA to the frrst peak with a pharmacological proftle characteristic for the A\(_2\) adenosine receptor as determined from adenylate cyclase experiments. In contrast, most adenosine receptor ligands did not compete for [\(^3\)H]NECA binding to the second, major peak. These results suggest that a solubilized A\(_2\) receptor-Gs protein complex of human platelets can be separated from other [\(^3\)H]NECA binding sites by gel filtration. This allows reliable radioligand binding studies of the A2 adenosine receptor of human plate1ets.
The effects of barbiturates on the GABA·receptor complex and the A\(_1\) adenosine receptor were studied. At the GABA-receptor complex the barbiturates inhibited the binding of [\(^{35}\)S]t-butylbicyclophosphorothionate [\(^{35}\)S]TBPT) and enhanced the binding of [\(^3\)H]diazepam. Kinetic and saturation experiments showed that both effects were allosteric. Whereas all barbiturates caused complete inhibition of [\(^{35}\)S]TBPT binding, they showed varying degrees of maximal enhancement of [\(^3\)H]diazepam binding; (±)methohexital was idenafied as the most efficacious compound for this enhancement. At the A\(_1\) adenosine receptor all barbiturates inhibited the binding of [\(^3\)H]N\(^6\)-phenylisopropyladenosine (\(^3\)H]PIA) in a competitive manner. The comparison of the effects on [\(^3\)H]diazepam and [\(^3\)H]PIA binding showed that excitatory barbiturates interact preferentially with the A\(_1\) adenosine receptor, and sedative/anaesthetic barbiturates with the GABA-receptor complex. It is speculated that the interaction with these two receptors might be the basis of the excitatory versus sedative/ anaesthetic properties of barbiturates.
The properties of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) as an antagonist ligand for A\(_1\) adenosirre receptors were examined and conipared with other radioligands for this receptor. DPCPX competitively antagonized both the inhibition of adenylate cyclase activity via A\(_1\) adenosirre receptors and the stimulationvia A\(_2\) adenosirre receptors. The K\(_i\)-values of this antagonism were 0.45 nM at the A\(_1\) receptor of rat fat cells, and 330 nM at the A\(_2\) receptor of human platelets, giving a more than 700-fold A\(_1\)-selectivity. A similar A\(_1\)-selectivity was determined in radioligand binding studies. Even at high concentrations, DPCPX did not significantly inhibit the soluble cAMPphosphodiesterase activity of human platelets. [\(^3\)H]DPCPX (105 Ci/mmol) bound in a saturable manner with high affinity to A\(_1\) receptors in membranes of bovine brain and heart, and rat brain and fat cells (K\(_D\) -values 50-190 pM). Its nonspecific binding was about 1% of total at K\(_D\) , except in bovine myocardial membranes (about 10%). Binding studies with bovine myocardial membranes allowed the analysis of both the high and low agonist affinity states of this receptor in a tissue with low receptor density. The binding properties of [\(^3\)H]DPCPX appear superior to those of other agonist and antagonist radioligands for the A\(_1\) receptor.
A\(_1\) adenosine receptors from different tissues and species we~e photoaffinity labelled and then the carbohydrate content was examined by both enzymatic and chemical treatment. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the labelled membrane receptors shows that neuraminidase treatment alters the electrophoretic mobility of the receptor band indica ting the presence of terminal neurandnie acids. Neuraminidase digestion does not influence the binding characteristics of the receptor. The totally deglycosylated receptor protein obtained by chemical treatment has an apparent molecular weight Of 32,000.
A\(_1\) adenosine receptors from rat brain membranes were solubilized with the zwitterionic detergent 3-[3-( cholamidopropyl)dimethylammonio]-1-propanesulfonate. The solubilized receptors retained all the characteristics of membrane-bound A\(_1\) adenosine receptors. A high and a low agonist affinity state for the radiolabelled agonist (R)-\(N^6\)-[\(^3\)H]phenylisopropyladenosine([\(^3\)H]PJA) with K\(_D\) values of 0.3 and 12 nM, respectively, were detected. High-affinity agonist binding was regulated by guanine nucleotides. In addition agonist binding was still modulated by divalent cations. The solubilized A\(_1\) adenosine receptors could be labelled not only with the agonist [\(^3\)H]PIA but also with the antagonist I ,3-diethyi-8-[\(^3\)H]phenylxanthine. Guanine nucleotides did not affect antagonist binding as reported for membrane-bound receptors. These results suggest that the solubilized receptors are still coupled to the guanine nucleotide binding protein N; and that all regulatory functions are retained on solubilization. Key Words: A1 adenosine receptors - Solubilization- Rat brain membranes. Klotz K.-N. et al. Characterization of the solubilized A1 adenosine receptor from rat brain membranes. J. Neurochem. 46, 1528-1534 (1986).