Regulation of Deoxyribonucleic Acid Synthesis in Bovine Adrenocortical Cells in Culture*

Abstract

Factors which regulate proliferation of adrenocortical cells have been investigated using mass cultures and clones of bovine cells. Fibroblast growth factor (FGF) and angiotensin II are the most potent mitogens identified for bovine adrenocortical cells; FGF exerts greater effects than angiotensin II. FGF and angiotensin II not only stimulate [³H]thymidine incorporation into DNA and the rate of cell proliferation but also increase the saturation density achieved. Although equivalent saturation densities occur with angiotensin II and FGF, cell overlapping occurs with FGF but not with angiotensin II. Insulin, multiplication stimulating activity, and somatomedin C are weak mitogens, increasing [³H]thymidine incorporation in DNA 2- to 3-fold when added at high concentrations. These agents potentiate FGF and angiotensin II mitogenic effects. Thrombin has weak stimulatory effects on DNA synthesis which are additive to those of FGF or angiotensin II. The interaction between angiotensin II and FGF was variable. Increasing concentrations of angiotensin II had no effect on DNA synthesis maximally stimulated by FGF or FGF plus insulin in uncloned cells and in two of five clones examined. In contrast, increasing concentrations of angiotensin II inhibited FGF-stimulated DNA synthesis down to the level observed with angiotensin II alone in three of five clones examined. A competitive inhibitor of angiotensin II, (Sar¹, He⁵, Ile⁸)angiotensin II, had no effect on FGF-stimulated DNA synthesis. These results suggest that FGF and angiotensin II differ in the mechanism through which they stimulate cell proliferation.