Influence of insulin on mitotic rate in cultivated mammalian cells

The influence of insulin (100 mU ml-1) on the mitotic rate in a tissue culture of muscle fibroblasts L was studied. The metod of temporary inhibition of cell transformation from G1 to S period with the aid of maintaining cells in serum free medium was used. Moreover, the number of mitoses in a stage of metaphasis after the addition of colchicine was counted and autoradiography was used. Insulin showed two independent effects on mitotic cycle: first it initiated the synthesis of DNA and increased the rate of a transformation of cells from a period G1 into period S; second--it increased the rate of processes at the final stages of mitotic cycle and increased the number of cells entering this cycle.