Pertussis toxin reverses the inhibition of insulin secretion caused by [Arg⁸]vasopressin in rat pancreatic islets

When rat pancreatic islets were incubated with 10(-8) M arginine vasopressin in the presence of 15 mM glucose there was a pronounced inhibition of insulin release in comparison with controls. This inhibitory effect appeared to be specific for vasopressin since it was antagonised by vasopressin antibody. Moreover, pertussis toxin (100 ng/ml) reversed the inhibition of insulin release due to vasopressin, indicating the possible involvement of a guanyl-nucleotide regulatory protein in the inhibitory effect. Nevertheless, 10(-8) M vasopressin increased islet concentrations of cyclic AMP even under conditions where insulin release was decreased.