Inhibitory action of phorbol myristate acetate on histamine secretion and polyphosphoinositide turnover induced by compound 48/80 in mast cells

Rat peritoneal mast cells which had been preincubated with phorbol myristate acetate (PMA, 10 - 100 ng/ml) for 5 min did not elicit the full histamine secretion induced by a potent secretagogue, compound 48/80. Furthermore, this PMA-treatment was found to inhibit the agonist-mediated hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) in [32P]labeled cells. However, it was also observed that the level of [32P]PIP2 was markedly reduced by 5 min-incubation with PMA. This suggests the enhanced hydrolysis of PIP2 by PMA which was reflected in a greater formation of inositol trisphosphate (IP3). These observations indicate that the formation of IP3 may not be profoundly related to secretory response in mast cells.