Effect of streptozotocin diabetes and insulin treatment on the rate of protein synthesis in tissues of the rat in vivo.

Constant infusion of [14C]tyrosine has been used to measure the fractional rates of protein synthesis in viuo in skeletal muscle, heart and liver of normal, streptozotocin diabetic and insulin-treated rats. Diabetes resulted in a 70% reduction in the rate of protein synthesis in skeletal muscle, and a 44 % reduction in that in heart. Insulin treatment increased the protein synthesis rate in both tissues in diabetic, but not in normal animals. Changes in the RNA to protein ratio in skeletal muscle and heart in response to diabetes and insulin treatment were qualitatively similar to those in the rate of protein synthesis, but were less pronounced. No effects of diabetes, insulin treatment, or fasting on the rate of synthesis of hepatic tissue proteins in vivo could be observed. Diabetes resulted in a slight fall in the RNA to protein ratio in liver. The results are discussed in the light of data from various laboratories on the effect of diabetes on protein synthesis in subcellular systems.