EFFECTS OF PROSTAGLANDINS ON SECRETION OF GLUCAGON AND INSULIN BY THE PERFUSED RAT PANCREAS

The secretion of both glucagon and insulin by the isolated perfused rat pancreas was significantly stimulated by 10-7 M PGH2. Experiments to show that the stimulated secretion was mediated by conversion of PGH2 to TXA2 or TXB2 revealed no correlation between the amount of secretion and the amount of thromboxane formed. Conversion of PGH2 with a crude platelet thromboxane synthase preparation caused a progressive loss of ability to secrete insulin, whereas the capacity to stimulate release of glucagon remained at about one-half the maximal level. This relatively stable and selective secretagogue action on the α-cells appeared to be due to the formation of PGD2 by the platelet preparation. Direct administration of PGD2 confirmed this interpretation and showed clearly that this prostaglandin is a potent secretagogue for glucagon with little activity in stimulating the release of insulin. Our results have shown high and relatively equal stimualtion of secretion by α- and β-cells with exogenous PGE2, PGF(2α), and PGH2, little or no secretion by either cell type with TXA2 TXB2, or PGI2, and a unique selective stimulatory action of PGD2 upon the α-cell.