INHIBITION OF HISTAMINE-SECRETION FROM MAST-CELLS BY LIPOXYGENASE ANDCYCLOOXYGENASE INHIBITORS

We have investigated the effect of inhibitors of lipoxygenase (LOX), c yclooxygenase (COX) and dual inhibitors of both enzymes on the degranu lation of peritoneal rat mast cells (pRMC) activated by different mech anisms. COX inhibitors weakly affected histamine secretion induced by A23187 and did not influence the histamine secretion induced by protam ine in an isotonic medium but blocked protamine-induced release in a h ypertonic medium. LOX- and dual-inhibitors inhibited secretion induced by A23187 and protamine under all conditions. As A23187 activates pRM C in an isotonic medium by Ca influx, and protamine acts in a hyperton ic medium by mobilization of intracellular Ca and in an isotonic mediu m by both processes (this paper), LOX but not COX inhibitors, may bloc k Ca influx, and both prevent Ca mobilization.