Inhibition o'f insulin release by cyproheptadine: effects on 3',5'-cyclic-AMP-content and 45Ca-accumulation of incubated mouse islets.

Cyproheptadine (1, 10 and 100 muM) significantly reduced insulin release from isolated mouse islets in response to glucose. In contrast, 1 mM cyproheptadine induced a large release of insulin into the incubation medium probably due to islet cell damage, since the islets had lost a considerable amount of their protein content. 3',5'-cyclic-AMP-levels of the islets were not significantly affected by 10 muM cyproheptadine in the presence as well as in the absence of theophylline (10 mM). As the inhibitory effect of cyproheptadine on insulin release was correlated with reduced accumulation of calcium-45, the agent may inhibit insulin release by interfering with the calcium handling of the beta-cell.