Secretory regulation of endocrine pancreas: Cyclic AMP and glucagon secretion

Activation of adrenergic beta receptors has been found to stimulate insulin release in vitro that may be mediated through the augmentation of cyclic AMP in the beta cell. The activation of adrenergic alpha receptors in the beta cell inhibits the insulin release. The present studies have shown that isoproterenol (0.62 mug/ml) and sodium dibutyryl cyclic AMP (50 mug/ml) stimulate the insulin secretion and inhibit the glucagon secretion in the presence of 50 mg/100 ml glucose by the isolated pancreatic perfusion of the rat, while norepinephrine (0.5 mug/ml) inhibits the insulin secretion induced by 150 mg/100 ml glucose and stimulates the glucaton secretion. Theophylline (50 mug/ml) does not stimulate the insulin and the glucagon secretion. When norepinephrine is added to theophylline, the output of glucagon does not occur. From these results it can be deduced that the pancreatic alpha cell function may be inhibited by elevation of intracellular cyclic AMP, in contrast to the beta cell function which is stimulated by an increment of cyclic AMP.