CELL-CYCLE TRAVERSE AND MACROMOLECULAR-SYNTHESIS IN BHK FIBROBLASTS AS AFFECTED BY INSULIN

Insulin produced a 10-fold activation of c[cyclic]AMP phosphodiesterase activity and a 3-fold reduction in cAMP content in serum-deprived, growth-arrested BHK [baby hamster kidney] fibroblasts. Insulin did not promote growth of these cells, as judged by measurement of cell number, but it did promote reentry of cells into the cell cycle and progression into S phase, as determined by rates of macromolecular synthesis and autoradiographic and microfluorometric analyses. Insulin stimulation of macromolecular synthesis can be blocked by the addition of a phosphodiesterase inhibitor, suggesting that these effects of insulin on the cell cycle may be mediated through its activation of cAMP phosphodiesterase.