[Somatomedin C: a factor of the differentiation of adrenal cortex cells].

Using a model of bovine adrenocortical cells cultured in a chemically defined medium, we have shown that pure biosynthetic IGF 1/SmC increases adrenal steroidogenic function. The treatment with increasing concentrations of SmC (0-200 ng/ml) increases the AII binding and synergizes the effect of AII on steroidogenesis. The maximal effect is observed with 50 ng/ml SmC for 48 hrs. This effect of SmC could not be attributable to a mitotic effect, since 100 ng/ml of SmC for 48 hrs., induced a very slight increase in DNA synthesis (X 1.2) without any modification of corticoadrenal cell number. Insulin mimics the steroidogenic effect of SmC, but only at high concentrations. The effects of these two hormones are not additive, suggesting a common step in their mechanism of action. In summary, SmC exerts a direct cytodifferentiating effect on adrenal steroidogenesis.