Studies on the stereoselectivity of the P2‐purinoceptor on the guinea‐pig vas deferens

Abstract

1 ATP, 2-chloro-ATP, 2-methylthio-ATP and their unnatural l-enantiomers, Rp and Sp diastereoisomers of the ATP phosphorothioate analogues, ATPαS and ATPβS, were tested on the guinea-pig vas deferens. 2 The 2-substituted analogues of ATP were no more effective than ATP in causing contraction of the vas deferens. However, stereoselectivity was observed with each pair of enantiomers of ATP, 2-chloro-ATP and 2-methylthio-ATP. 3 No stereoselectivity was observed for the phosphorothioate analogues. Rp- and Sp-ATPβS were more effective than ATP at eliciting contractions of the vas deferens. 4 These results show that unlike the P₂-purinoceptor mediating excitatory responses in the guinea-pig bladder, the P₂-purinoceptor mediating contraction in the guinea-pig vas deferens displays stereoselectivity.