2 TYPES OF PROSTACYCLIN RECEPTOR COUPLING TO STIMULATION OF ADENYLATE-CYCLASE AND PHOSPHATIDYLINOSITOL HYDROLYSIS IN A CULTURED MAST-CELL LINE, BNU-2C13 CELLS

Prostacyclin (PGI2)-mediated signal transduction was examined in interleukin 3 (IL-3)-dependent BNu-2cl3 mast cells. Iloprost, a stable PGI2 analogue, induced the accumulation of intracellular cAMP and IP3, and an increase in the intracellular Ca2+ concentration. Pretreatment of the cells with a protein kinase C activator, 12-O-tetradecanoyl phorbol 13-acetate, suppressed the iloprost-induced IP3 accumulation and Ca2+ mobilization, but inversely potentiated the cAMP accumulation, suggesting that neither of these signal transduction pathways of iloprosts is the result of a secondary effect of activation of the other. Removal of IL-3 from the culture medium reduced the iloprost-induced IP3 accumulation and Ca'' mobilization, while it had no effect on the iloprost-induced cAMP accumulation at all. These results taken together suggest that BNu-2cl3 cells express two types of PGI2 receptor; one couples to stimulation of adenylate cyclase, its expression being independent of IL-3, while the other couples to phosphatidylinositol hydrolysis, its expression being dependent on IL-3.