2-Alkylthio-substituted platelet P2Y 12 receptor antagonists reveal pharmacological identity between the rat brain G i-linked ADP receptors and P2Y 12

Abstract

The G i-linked platelet ADP receptor, now designated as P2Y 12, accounts for ADP-induced inhibition of adenylyl cyclase in platelets and certain clonal rat cell lines. The pharmacology of this receptor is well characterized. Based on the functional approach of [ 35S]GTPγS autoradiography, we recently disclosed the widespread presence of G i-linked ADP receptors in the rat nervous system. Based on initial pharmacological analysis, these receptors were strikingly similar with P2Y 12. Here, we extend this analysis by comparing the potencies of six 2-alkylthio-substituted ATP analogues, including the adenosine-aspartate conjugate 2-hexylthio-AdoOC(O)Asp 2 and five AR-C compounds (AR-C67085, AR-C69931, AR-C78511, AR-C69581, AR-C70300) with wide range of affinities towards P2Y 12, in reversing 2-methylthio-ADP stimulated G protein activity in rat brain sections and human platelet membranes. Closely matching pIC 50 values ( r 2=0.99) revealed pharmacological similarity between the two receptors with one exception: AR-C67085 more avidly recognized the platelet P2Y 12. Further analysis of the rat brain pIC 50 data against those available for three of the AR-C compounds in reversing P2Y 12-mediated adenylyl cyclase inhibition in rat platelets ( r 2=0.96) and rat C6 glioma cells ( r 2=1.00) demonstrated that the three P2Y receptors are pharmacologically indistinguishable. We conclude that the rat brain G i-linked ADP receptors, as revealed using [ 35S]GTPγS autoradiography, correspond to P2Y 12.