HYPOPHYSIS AND FUNCTION OF PANCREATIC ISLETS

Abstract

ABSTRACT The effects of the recognized diabetogenic hormones, growth hormone and ACTH, administered in vivo, on (pro-)insulin biosynthesis and secretion in isolated islets of normal rats were studied. Rats were treated with these hormones for 4 weeks. Afterwards, their collagenase-isolated islets were incubated with [3H]leucine for 3 h. (Pro-)Insulin biosynthesis was estimated for the incorporation data into islet protein fractions. Islets of treated rats released significantly more insulin and incorporated significantly less [3H]leucine into proinsulin and insulin compared with controls when tested at 100 mg glucose/100 ml. At 200 mg glucose/100 ml, no significant differences were found. The findings demonstrate an impact of these hormones on the B-cells derived from normal pancreas of intact rats. The alterations are, however, not very pronounced and can be easily compensated under a strong glucose stimulus. It appears that the mechanisms for (pro-)insulin biosynthesis and release in rats are more resistant against the diabetogenic actions of pituitary hormones than in other species.