PRIOR GLUCOSE DEPRIVATION INCREASES THE FIRST-PHASE OF GLUCOSE-INDUCED INSULIN-RESPONSE - POSSIBLE INVOLVEMENT OF ENDOGENOUS ATP AND (OR) ADP

A possible implication of endogenously released ATP and (or) ADP in in sulin response to glucose stimulation was investigated in the isolated rat pancreas. The first phase of insulin response to the same glucose concentration (8.3 mM) was much higher in pancreas previously perfuse d in the absence of glucose than in pancreas previously perfused with 4.2 mM glucose. A P-2 purinoceptor antagonist, 2,2'-pyridylisatogen to sylate, strongly reduced the higher first phase resulting from glucose deprivation; similarly, it reduced exogenous ATP-potentiated insulin response to a glucose increase from 4.2 to 8.3 mM. In contrast, 2,2'-p yridylisatogen tosylate did not modify the first phase of insulin resp onse to 8.3 or 12.5 mM glucose in pancreas previously perfused with 4. 2 mM glucose. Our results suggest that endogenous ATP and (or) ADP rel eased in pancreatic islets in the absence of glucose could activate P- 2 purinoceptors and increase the magnitude of the first phase of insul in response to a glucose stimulation.