[The effect of insulin on protein synthesis and secretion in primary liver cultures]

The effects of insulin on the rates of synthesis of intracellular and secreted proteins have been studied in primary cultures of fetal rat hepatocytes. During 3-h incubation with the hormone and 14C-L-leucine similar stimulation of synthesis of both intracellular and secreted protein was observed. Insulin did not affect significantly the proportion of 14C-labelled proteins destined for secretion in the cell cultures grown on standard nutrient medium, as well as on selective medium containing phenobarbital and cortisol. The results obtained show that the major part (85-90%) of newly synthesized proteins remains inside the cells. Therefore, biological testing of insulin or its synthetic analogs on hepatocyte cultures may be limited by the estimation of the rate of biosynthesis of intracellular proteins only.