Insulin Release during Alpha-Adrenergic Receptor Blockade: Primacy of the Glycemic Stimulus

Insulin release during alpha-adrenergic receptor blockade in a variety of experimental animals has raised the possibility of a direct effect of alpha-blockade on insulin secretion. However, in 7 unanesthetized baboons, an increase in the serum insulin concentration during phentolamine-induce alpha- adrenergic receptor blockade occurred only in hyperglycemic animals and the magnitude of the increase in serum insulin was significantly correlated with the serum glucose concentration immediately prior to phentolamine. These findings are consistent with observations showing no effect of alpha-adrenergic inhibitors on basal insulin concentration in (normoglycemic) man and indicate that insulin secretion during alpha-adrenergic receptor blockade occurs only in the presence of an appropriate glycemic stimulus. Pub. in Endocrinology, v89 n3 p918 920 Sep 1971.