Pharmacological evaluation and chemical stability of 2-benzylthioether-5 '-O-(1-thiotriphosphate)-adenosine, a new insulin secretagogue acting through P2Y receptors

Activation of P2Y receptors on pancreatic beta -cells by extracellular ATP bring about amplification of glucose-induced insulin secretion, which has b een shown to reduce hyperglycemia in vivo. A new P2 receptor ligand, 2-benz ylthio-ATP-alpha -S, was synthesized based on a combination of modification s of the ATP skeleton, as a potential insulin secretagogue. The two diaster eoisomers of this ligand were separated and are designated A and B. The eff ects of these compounds on insulin secretion and vascular resistance in the rat isolated and perfused pancreas were evaluated in the presence of a sli ghtly stimulating glucose concentration (8.3 mM) and were compared with ATP -alpha -S and ATP. Both isomers of 2-benzylthio-ATP-a-S (0.015-1.5 muM) ind uced a concentration-dependent increase in glucose-induced insulin release. The potency of isomer A was not significantly different from that of isome r B, and both were approximately 100-fold more potent than ATR ATP-alpha -S induced a similar pattern of insulin response; however, it was only approx imately 10-fold more potent than ATR These compounds also induced vascular effects: ATP-alpha -S induced a vasodilatation and was transiently vasocons trictor only at a high concentration, whereas the C2-substituted derivative constantly induced a vasoconstriction. The chemical stability of these lig ands was evaluated under physiological conditions and gastric juice PH. Hyd rolysis of 2-benzylthio-ATP-alpha -S has been studied both in PH 7.4 and PH 1.4 at 37 degreesC using P-31 nuclear magnetic resonance (NMR) spectroscop y and high-performance liquid chromatography. This compound exhibited high chemical stability with respect to hydrolysis of the glycosidic bond and de sulfurization of the phosphorothioate moiety. Hydrolysis of the phospho est er bond, which was the only detectable degrading reaction under the investi gation conditions (PH 7.4, 37 degreesC), was slow, with a half-life of 264 h. Moreover, even at gastric juice conditions (PH 1.4, 37 degreesC), hydrol ysis of the terminal phosphate was the only detectable reaction, with half- life of 17.5 h. in conclusion, both isomers of 2-benzylthio-ATP-alpha -S ar e soluble in water and highly chemically stable. These compounds are highly potent and effective insulin secretagogues; however, they increase pancrea tic vascular resistance. (C) 2001 Wiley-Liss, Inc.