INHIBITORY EFFECT OF SOMATOSTATIN ON INSULIN SECRETION DURING α-ADRENERGIC BLOCKADE IN THREE DIFFERENT SPECIES

Abstract

ABSTRACT It has recently been suggested from experiments in dogs that somatostatin suppresses insulin release via a stimulation of the inhibitory α-adrenoceptors of the pancreatic B-cell. The effect of somatostatin on insulin secretion during α-adrenergic blockade with phentolamine was therefore studied in three different species; the rat, the cat and the mouse. It was found that somatostatin significantly depressed insulin release during α-adrenoceptor blockade in all three species. In the rat, infusion of somatostatin at a dose of 0.3 μg/kg/min decreased basal plasma insulin concentration by 92 %. In the presence of phentolamine, the same dose of somatostatin lowered plasma insulin by 85 %. In the cat, a similar infusion of somatostatin lowered basal plasma insulin concentration by 87 %, but its depressive effect during α-adrenergic blockade was comparatively less pronounced (68 %) than in the rat. In the mouse, a single iv injection of somatostatin induced a short-lasting depression of plasma insulin concentration during α-adrenergic blockade. From these results it seems unlikely that somatostatin should inhibit insulin release simply by stimulation of α-adrenoceptors on the B-cell. It cannot be ruled out, however, that a more complex interaction exists between somatostatin and the sympatho-adrenal system with regard to the control of insulin secretion.