STIMULATION BY INSULIN OF PROTEIN-SYNTHESIS IN CULTURED CHICK-EMBRYO FIBROBLASTS

Insulin stimulates protein synthesis in skeletal muscle of young anima ls and has been reported to exert similar effects on a variety of mamm alian cell types in culture. However, with chick embryo fibroblasts we found that the extent of this effect was very sensitive to the cultur e conditions of the cells prior to the insulin treatment. The most rep roducible results were obtained with cells that had been sub-cultured into medium in which fetal calf serum was replaced with 2% horse serum . Insulin only stimulated protein synthesis when added at supra-physio logical concentrations. Insulin-like growth factor 1 was effective at much lower concentrations. Since chick embryo fibroblasts can be obtai ned in good yield, they offer, if treated under appropriate conditions , a suitable system for study of the mechanisms by which insulin and I GF-1 promote the initiation of protein synthesis in eukaryotic cells.