Hypophysis and function of pancreatic islets. IV. Effect of treatment with growth hormone and corticotrophin on insulin secretion and biosynthesis in isolated pancreatic islets of normal rats.

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.