Pharmacological study of phospholipase A2-induced histamine release from rat peritoneal mast cells

The effect of some drugs on phospholipase A2 (PLA2)-induced histamine release from rat peritoneal mast cells was investigated. 1. PLA2 (Naja naja) caused the release of histamine from rat peritoneal mast cells in a dose related fashion. 2. The release of histamine by PLA2 was decreased by the removal of each of calcium and glucose from the reaction medium (Tyrode's solution). 3. p-Bromophenacyl bromide and mepacrine, PLA2 inhibitors, inhibited the release of histamine caused by PLA2. 4. Cinnarizine and nifedipine, calcium channel blockers, and oxatomide, KC-404, tranilast and disodium cromoglycate, anti-allergic agents, also inhibited the PLA2-induced histamine release. 5. When prednisolone (0.5 mg/kg) was administered i.p. 2, 3 and 4 h prior to the harvest of the mast cells, the amount of histamine released by PLA2 ex vivo was significantly decreased. Hydrocortisone, prednisolone and dexamethasone clearly inhibited the release of histamine from mast cells when they were administered 4 h prior to harvest of the cells.