Insulin effect on [14C]-valine incorporation and its relation to hexokinase activity in developing brain.

Using minced brain cortex from fetal and postnatal rats, we studied the incorporation of [14C]-valine into protein in the presence of insulin. We also assayed the "particle bound" and soluble hexokinase in these tissues. Insulin significantly stimulated the incorporation of [14C]-valine into brain proteins from fetal stage upto 2 days of life. After this period the insulin effect was minimal, with no effect by day 5. The "particle bound" (40,000g pellet) brain hexokinase, on the other hand, remained low till about 2 days of life and then increased to almost adult level by 5 days. Our results show that there is an inverse relation between this anabolic effect of insulin and the "particle bound" hexokinase activity in the cortex of developing rat brain.