Cell cycle specific fluctuations of adenosine 3',5'-monophosphate and prostaglandin binding in synchronized mastocytoma P-815 cells

Abstract

Endogenous adenosine 3',5'-monophosphate (cAMP) levels in mastocytoma P-815 cells, synchronized either at the G 1/S transition by amethopterin- or double thymidine-block or in mitosis by colcemid block, were highest during late S and early G 2 phases and lowest during mitosis. These cell cycle-dependent changes in cAMP levels were largely accounted for by the changes in adenylate cyclase and phosphodiesterase activities. Similar fluctuations occurred simultaneously with specific prostaglandin E 1 (PGE 1) binding, histidine decarboxylase activity, histamine content, and [ 35S]SO 4 2− incorporation into glycosaminoglycans of the cells. In addition, endogenous levels of the E group of prostaglandins (PGEs) and [ 14C]arachidonic acid incorporations into PGE, phosphatidylcholine and phosphatidylinositol also exhibited fluctuation patterns similar to that of cAMP levels. Since cAMP levels still fluctuated in a serum-depleted medium where DNA synthesis and cell division were inhibited, endogeneous levels of prostaglandin and cAMP appeared not to be regulated solely by serum factor(s). Exposure of cells at G 1/S transition to 1-methyl-3-isobutylxanthine (MIX) resulted in a 10-fold elevation of cAMP levels throughout the cell cycle without affecting DNA synthesis. On the other hand, PGE 1 and/or MIX added at late S phase elevated cAMP levels, prolonged G 2 phase and retarded the cell division, but these agents added at the beginning of mitosis elevated cAMP levels without affecting the cell division. These results suggest that prostaglandins newly synthesized by the increased metabolism of phospholipids promote the cAMP synthesis via their binding to the receptors and thereby control the division and phenotypic expression of mastocytoma P-815 cells.