Calcium antagonists and hormone release. VI. Effects of a calcium antagonist (verapamil) on the biphasic insulin release in vivo.

The present study was designed to investigate the influence of a calcium antagonist (verapamil) on the two phases of insulin release. The present results confirmed our previous studies and in vitro data, showing that the first phase insulin release is not inhibited by a calcium antagonist and strongly indicated that glucose stimulated insulin secretion has two phases of release: (1) the first phase of release, which is independent from extracellular calcium; (2) the second phase of release, which was inhibited by calcium antagonists, is dependent from calcium uptake from an extracellular source.