RESUMO
The chronic effect of insulin on the expression of the glycogen synthase kinase-3 alpha gene in streptozotocin-induced diabetic rat liver is examined. The mRNA levels of glycogen synthase kinase-3 alpha were increased (143% of normal levels) in diabetic livers and these were normalized by insulin supplementation to the diabetic animals. Neither diabetes nor insulin supplementation to diabetic rats altered the transcription rate of glycogen synthase kinase-3 alpha. However, diabetes caused an increase in the half-life of glycogen synthase kinase-3 alpha mRNA from 5 h in normal hepatocytes to 8 h in diabetic ones. Insulin supplementation to the incubation medium of diabetic hepatocytes decreased the half-life of glycogen synthase kinase-3 alpha mRNA to a level comparable with normal values. This study suggests that the chronic effect of insulin decreases the levels of glycogen synthase kinase-3 alpha mRNA by altering its stability.