TY  - JOUR
A1  - Koch, R.
A1  - Deger, A.
A1  - Klotz, Karl-Norbert
A1  - Schenzle, D.
A1  - Krämer, H.
A1  - Kelm, S.
A1  - Müller, G.
A1  - Rapp, R.
A1  - Weber, U.
T1  - Characterization of solubilized insulin receptors from rat liver microsomes. Existence of two receptor species with  different binding properties
N2  - Insulin receptors were solubilized from rat liver microsomes by the nonionic detergent Triton X-100. After gel filtration of the extract on Sepharose CL-6B, two insulin-binding species (peak I and peak li) were obtained. The structure and binding properties of both peaks were characterized. Gel filtration yielded Stokes radii of 9.2 nm (peak I) and 8.0 nm (peak Il). Both peaks were glycoproteins. At 4°C peak 1 showed optimal insulin binding at pH 8.0 and high ionic strength. In contrast, peak li bad its binding optimum at pH 7.0 and low ionic strength, where peak I bindingwas minimal. For peak I the change in insulin binding under different conditions of pH and ionic strength was due to a change in receptor affinity only. For peak 11 an additional change in receptor number was found. Both peaks yielded non-linear Scatchard plots under most of the buffer conditions examined. At their binding optima at 4 oc the high affinity dissociation constants were 0.50 nM (peak I) and 0.55 nM (peak II). Sodium dodecyl sulfatejpolyacrylamide gel electrophoresis of peak I revealed five receptor bands with Mr 400000, 365000, 320000, 290000, and 245000 under non-reducing conditions. For peak II two major receptor bands with M\(_r\) 210000 and 115000 were found. The peak II receptor bands were also obtained aftermild reduction of peak I. After complete reduction both peaks showed one major receptor band with M\(_r\) 130000. The reductive generation of the peak II receptor together with molecular mass estimations suggest that the peak I receptor is the disulfide-linked dimer of the peak II receptor. Thus, Triton extracts from rat liver microsomes contain two receptor species, which are related, but differ considerably in their size and insulin-binding properties.
KW  - Toxikologie
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60215
ER  - 
TY  - JOUR
A1  - Adam, W.
A1  - Ahrweiler, M.
A1  - Saha-Möller, C. R.
A1  - Sauter, M.
A1  - Schönberger, A.
A1  - Epe, B.
A1  - Müller, E.
A1  - Schiffmann, D.
A1  - Stopper, Helga
A1  - Wild, D.
T1  - Genotoxicity studies of benzofuran dioxetanes and epoxides with isolated DNA, bacteria and mammalian cells
N2  - 1.2-Dioxetanes, very reactive and high energy molecules. are involved as labile intermediates in dioxygenase- activated aerobic metabolism and in physiological processes. Various toxico1ogica1 tests reveal that dioxetanes are indeed genotoxic. In supercoiled DNA of bacteriophage PM2 they induce endonucleasesensitive sites, most of them are FPG protein-sensitive base modifications (8-hydroxyguanine, fonnamidopyrimidines). Pyrimidinedimersand sites ofbase loss (AP sites) which were probed by UV endonuclease and exonuclease 111 are minor lesions in this system. While the alky1-substituted dioxetanes do not show any significant mutagenic activity in different Salmonella typhimurium strains, heteroarene dioxetanes such as benzofuran and furocoumarin dioxetanes are strongly mutagenic in S. typhimurium strain TA I 00. DNA adducts formed with an intermediary alkyJating agent appear to be responsible for the mutagenic activity of benzofuran dioxetane. We assume that the benzofuran epoxides, generated in situ from benzofuran dioxetanes by deoxygenation are the ultimate mutagens of the latter. since benzofuran epoxides are highly mutagenic in the S. typhimurium strain TAIOO and they form DNA adducts. as detected by the 212Ppostlabelling technique. Our results imply that the type of D NA darnage promoted by dioxetanes is dependent on the structural feature of dioxetanes. Furthermore, the direct photochemical DNA darnage by energy transfer. i.e., pyrimidine dimers, plays a minor role in the genotoxicity of dioxetanes. Instead, photooxidation dominates in isolated DNA. while radical darnage and alkylation prevail in the cellular system.
KW  - Toxikologie
KW  - 1
KW  - 2-Dioxetane
KW  - Benzefuran dioxetane
KW  - Benzefuran epoxide
KW  - DNA damage
KW  - Mutagenicity
KW  - DNA adduct . Repair endonuclease
KW  - FPG protein
Y1  - 1993
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63420
ER  -