Fibroblasts as an Experimental Tool in Metabolic and Hormone Studies

The effects of insulin and purified nonsuppressible insulin‐like activity from serum (NSILA‐S) on glucose, DNA‐metabolism and growth of chicken embryo fibroblasts are compared. Insulin stimulates growth, glucose consumption, lactate production and thymidine uptake only in very high concentrations (1–100 mU/ml), whereas NSILA‐S is effective at concentrations which may be present under physiological conditions. On a molar basis NSILA‐S is approximately 20 times as active as insulin. Although a potent stimulator of all these metabolic indices NSILA‐S can only partially replace serum. NSILA‐S may be one of the growth factors present in serum but it does not seem to be the only one.