Effects of Glucose on Insulin Biosynthesis in Foetal and Newborn Rats

Abstract

Studies on the incorporation of ³H-leucine into proinsulin and insulin were performed on pancreatic islets isolated from rat foetuses at day 21 1/2 of gestation and from newborn rats at one and six days of age. Acid ethanol-soluble proteins of the islets were partially purified and subsequently separated on a Sephadex G-50 column. The incorporation of radioactive leucine into proinsulin was enhanced already after 15 min of incubation in all the three age groups when the concentration of glucose in the incubation medium was increased from 0.4 to 3.0 mg/ml. After 60 and 180 min of incubation, a stimulatory effect of high glucose concentrations on the leucine incorporation into insulin was also observed in all the three age groups. The stimulatory effect of glucose on the biosynthesis of insulin in the rat during late foetal and early neonatal life contrasts with the relatively low efficiency of glucose as a stimulant for insulin secretion before the second postnatal day.

Key words

Isolated Pancreatic Islets - Glucose Effects on Pancreatic Islets - Insulin Biosynthesis - Proinsulin - Perinatal Rats