Insulin effect on the cell cycle: analysis of the kinetics of growth parameters in confluent chick cells

Several techniques, including flow microfluorometry, were utilized to study the effect of insulin on the growth of cultured cells. It was demonstrated that chick fibroblasts can be stimulated to synthesize DNA and undergo mitosis after insulin addition. The kinetics of the cell movement through the cell cycle as well as the length of the cycle itself, however, were distinctly different in insulin- and serum-treated cultures. The insulin-treated cells had a shorter G1, an extended S, and a much extended G2 residence time compared to cells treated with serum. A model of growth regulation which includes both primary cultures and cell lines is proposed.