Effect of serum concentration on adenylate cyclase activities of untransformed BHK cells and polyoma virus-transformed derivatives.

Adenylate cyclase activities of untransformed hamster BHK 21/13 cells and their polyoma virus-transformed derivatives were compared using the cells cultured in low and high serum concentrations. The untransformed cells that were cultured in a medium containing 10% serum had a slightly higher activity than the transformed cells cultured under the same conditions. When the cells were cultured in a medium containing 0.5% serum that stopped proliferation of untransformed cells, more significant difference was observed in the adenylate cyclase activity; the untransformed cells had a two-fold higher activity than the transformed cells. The full activity measured in the presence of fluoride was two-fold higher in the untransformed than in the transformed cells. The low serum concentration increased the enzyme activity of both untransformed and transformed cells, but the enzyme activity of transformed cells in the presence of 0.5% serum did not exceed the activity of untransformed cells in 10% serum. Intracellular cyclic AMP levels were in parallel with the activity of adenylate cyclase, whereas no correlation was found between cyclic AMP levels and cyclic AMP phosphodiesterase activities.