The control of growth of mouse mastocytoma cells by N6,O2'-dibutyryladenosine cyclic 3',5'-monophosphate.

Addition of N6,O2'-Dibutyryladenosine cyclic 3',5'-monophosphate (DB cyclic AMP) plus theophylline or transfer to medium containing 0.2% serum slowed the growth of cultured mouse mastocytoma cells and eventually arrested their growth in G1 phase. Examination of the properties of cells arrested by either procedure suggested that the drugs arrested cells in G1 phase 1.5-2 h after the point of low serum arrest. Cycloheximide prevented the recovery of cell growth after low serum or drug-induced arrest demonstrating that protein synthesis was necessary to pass either growth restriction point. Cordycepin also prevented drug-arrested cells from progressing into cycle indicating a requirement for RNA synthesis to overcome the drug-induced growth arrest. Evidence is also presented that DB cyclic AMP prevented the cells receiving a pulse of calcium necessary to proceed past the DB cyclic AMP-sensitive growth restriction point. It is suggested that high cyclic AMP levels prevent mastocytoma cells from receiving a surge of calcium in G1 phase that is necessary if the cells are to proceed to S phase and eventually divide.