Effect of diltiazem on insulin secretion. II. Experiments on perfused rat pancreas, anesthetized dogs and conscious rats.

Effect of diltiazem on insulin secretion was investigated in the perfused rat pancreas. Experiments were also carried out in anesthetized dogs and conscious rats with and without glucose loading. In the perfused rat pancreas, diltiazem reduced both glucose- and tolbutamide-induced insulin secretion and these effects of diltiazem were reversed with removal of the compound. Inhibition of the glucose-induced insulin secretion caused by diltiazem was counteracted by increasing the concentration of calcium ion. In experiments on intact animals, diltiazem at vasoactive doses produced no significant influence on the basal level of plasma insulin or glucose-induced insulin secretion. These data taken together with findings in previously reported work suggest that diltiazem reduces insulin secretion from pancreatic B-cells in vitro possibly by the calcium-antagonistic property, while the compound exhibits practically no inhibitory action on the insulin secretion in vivo.