ADENOSINE-5'-O-(2-THIODIPHOSPHATE) IS A POTENT AGONIST AT P2 PURINOCEPTORS MEDIATING INSULIN-SECRETION FROM PERFUSED RAT PANCREAS

1 The effects of a P2 purinoceptor agonist, adenosine 5'-O-(2-thiodiphosphate) (ADP-beta-S) have been studied on insulin secretion and flow rate of the isolated perfused pancreas of the rat. 2 In the presence of a moderately stimulating glucose concentration (8.3 mM), ADP-beta-S (4.95-495 nM) evoked a biphasic insulin response in a concentration-dependent manner. A comparison of relative potency between ADP-beta-S and adenosine 5'-triphosphate (ATP) showed that ADP-beta-S was 100 times more potent than ATP. On the other hand, in the presence of a non stimulatory glucose concentration (4.2 mM), ADP-beta-S (165 nM) did not modify the basal insulin secretion. 3 ADP-beta-S, at concentrations effective on insulin secretion and also at higher concentrations (1.65 and 16.5-mu-M), provoked an increase of the pancreatic flow rate in a concentration-dependent manner. 4 Our results show that ADP-beta-S is a potent insulin secretory P2 purinoceptor agonist. As it is resistant to hydrolysis it might be useful in studying the effect of activation of the P2 purinoceptor of beta cells on insulin secretion in vivo.