Insulin secretion and biosynthesis in sucrose fed rats.

Long term feeding of a sucrose rich diet to rats is accompanied by a decreased glucose assimilation rate, despite high plasma insulin levels. Hyperinsulinism is at least partially based on a relative obesity, with increased amounts of abdominal- and retroperitoneal fat tissue, but unchanged total body weight compared to starch fed controls. The secretory pattern of insulin release was studied following glucose, arginine, fructose and sulfonylurea administration in the isolated perfused pancreas of sucrose and isocaloric starch fed rats.

(Pro-) insulin biosynthesis and release of newly synthesized (pro-) insulin from isolated islets of rat pancreas in the presence of amino acids and sulphonylureas.

The influence of arginine, lysine, tolbutamide and glibenclamide on (pro-) insulin biosynthesis and release of newly synthesized (pro-) insulin was studied in isolated islets of rat pancreas. Islets were incubated with 3H-leucine and glucose in the presence and absence of the test agents. Proinsulin and insulin of islets and incubation media were separated by gel filtration on Sephadex G 50.

Somatostatin-induced inhibition of insulin secretion from isolated islets of rat pancreas in presence of glucagon.

In order to study the oeffect of somatostatin on the endocrine pancreas directly, islets isolated from rat pancreas by collagenase were incubated for 2 hrs 1) at 50 and 200 mg/100 ml glucose in the absence and presence of somatostatin (1, 10 and 100 mg/ml) and2) at 200 mg/100 ml glucose together with glucagon (5 mug/ml), with or without somatostatin (100 ng/ml). Immunologically measurable insulin was determined in the incubation media at 0, 1 and 2 hrs. Insulin release was not statistically affected by any concentration stomatostatin.

Insulin biosynthesis in isolated pancreatic islets of fetal and newborn rats.

The effect of glucose and glucose plus glucagon on the incorporation of H-3-L-leucine into proinsulin and insulin was examined in isolated islets of twenty-one-day old fetal and five- and ten-day old newborn rats. Maximal stimulation of (pro-) insulin biosynthesis was achieved with 100 mg. per cent of glucose in isolated islets of twenty-one-day old fetal rats.