@article{GonzalesCaleroCuberoKlotz1992,
  author    = {Gonzales-Calero, G. and Cubero, A. and Klotz, Karl-Norbert},
  title     = {G protein coupled A\(_1\) adenosine receptors in coated vesicles of mammalian brain. Characterization by radioligand binding and photoaffinity labeling},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-60435},
  year      = {1992},
  abstract  = {A\(_1\) adenosine receptors in coated vesicles have been characterized by radioligand binding and photoaflinity labelling. Saturation experiments with the antagonist 8-cyclopentyl-1 ,3-[\(^3\)H]dipropyl-xanthine ([\(^3\)H]DPCPX) gave a Kdvalue of 0.7 nM and a Bmax value of 82± 13 fmol/mg protein. For the highly A\(_1\)-selective agonist 2-chloro-N\(^6\)-[\(^3\)H]cyclopentyladenosine ([\(^3\)H]CCPA) a Kd value of 1.7 nM and a Bmax value of 72 ± 29 fmol/mg protein was estimated. Competition of agonists for [\(^3\)H]DPCPX binding gave a pharmacological profile with R-N\(^6\)-phenylisopropyladenosine (R-PIA) > CCPA > S-PIA > 5'-N-ethylcarboxamidoadenosine (NECA), which is identical to brain membranes. The competition curves were best fitted according to a two-site model, suggesting the existence of two affinity states. GTP shifted the competition curve for CCP A to the right and only one affinity state similar to the low affinity state in the absence of GTP was detected. The photoreactive agonist 2-azido-N\(^6\)- \(^{125}\)I-p-hydroxyphenylisopropyladenosine ([\(^{125}\)I]AHPIA) specifically labelled a single protein with an apparent molecular weight of 35,000 in coated vesicles, which is identical to A\(_1\) receptors labelled in brain membranes. Therefore, coated vesicles contain A\(_1\) adenosine receptors with similar binding characteristics as membrane-bound receptors, including GTP-sensitive high-affinity agonist binding. Photoaffinity labelling data suggest that A\(_1\) receptors in these vesicles are not a processed receptor fonn. These results confirm that A\(_1\) receptors in coated vesicles are coupled to a G-protein, and it appears that the A\(_1\) receptor systems in coated vesicles andin plasma membranes are identical.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{NolteLorenzenLehretal.1992,
  author    = {Nolte, D. and Lorenzen, A. and Lehr, H.-A. and Zimmer, F.-J. and Klotz, Karl-Norbert and Messmer, K.},
  title     = {Reduction of postischemic leukocyte-endothelium interaction by adenosine via A\(_2\) receptor},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-60424},
  year      = {1992},
  abstract  = {The adhesion of leukocytes to the endothelium of postcapillary venules hallmarks a key event in ischemia-reperfusion injury. Adenosine has been shown to protect from postischemic reperfusion injury, presumably through inhibition of postischemic leukocyte-endothelial interaction. This study was performed to investigate in vivo by which receptors the effect of adenosine on postischemic leukocyte-endothelium interaction is mediated. The hamster dorsal skinfold model and fluorescence microscopy were used for intravital investigation of red cell velocity, vessel diameter, and leukocyte-endothelium interaction in postcapillary venules of a thin striated skin muscle. leukocytes were stained in vivo with acridine orange (0.5 mg kg\(^{-1}\) min\(^{-1}\) i.v. ). Parameters were assessed prior to induction of 4 h ischemia to the muscle tissue and 0.5 h, 2 h, and 24 h after reperfusion. ·Adenosine, the adenosine A1-selective agonist 2-chloro-N\(^6\) -cyclopentyladenosine (CCPA), the Arselective agonist CGS 21,680, the non-selective adenosine receptor antagonist xanthine amine congener {XAC), and the adenosine uptake blocker S-(p-nitrobenzyl)-6-thioinosine (NBTI) were infused viajugular vein starting 15 min priortorelease of ischemia until 0.5 h after reperfusion. Adenosine and CGS 21,680 significantly reduced postischemic leukocyte-endothelium interaction 0.5 h after reperfusion (p< 0.01), while no inhibitory effect was observed with CCPA. Coadministration of XAC blocked the inhibitory effects of adenosine. Infusion of NBTI alone effectively decreased postischemic leukocyte-endothelium interaction. These findings indicate that adenosine reduces postischemic leukocyte-endothelium interaction via A\(_2\) receptor and suggest a protective role of endogenous adenosine during ischemia-reperfusion.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{CristalliEleuteriVittorietal.1992,
  author    = {Cristalli, G. and Eleuteri, A. and Vittori, S. and Volpini, R. and Lohse, M. J. and Klotz, Karl-Norbert},
  title     = {2-Alkynyl derivatives of adenosine and adenosine-5'-N-ethyluronamides as selective agonists at A\(_2\) adenosine receptors},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-60412},
  year      = {1992},
  abstract  = {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.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{BommakantiBokochTolleyetal.1992,
  author    = {Bommakanti, R. and Bokoch, G. M. and Tolley, J. O. and Schreiber, R. E. and Siemsen, D. W. and Klotz, Karl-Norbert and Jesaitis, A. J.},
  title     = {Reconstitution of a physical complex between the N-formyl chemotactic peptide receptor and G protein: Inhibition by pertussis toxin-catalyzed ADP ribosylation},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-60406},
  year      = {1992},
  abstract  = {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.},
  subject      = {Toxikologie},
  language  = {en}
}