Edema formation and degranulation of mast cells by Trimeresurus mucrosquamatus snake venom.

Trimeresurus mucrosquamatus venom, carrageenin, compound 48/80, trypsin and bovine serum albumin were injected s.c. into the plantar muscle to induce edema formation in the hind paw of rats. The venom was the most potent, and it and compound 48/80 induced the maximum swelling rate of edema within 15 - 30 min after injection. The edema volume induced by the venom was dose-dependent between 2.5 and 10 micrograms. Hydrocortisone, phenylbutazone, indomethacin and diphenhydramine inhibited edema induced by the venom and other inflammatory agents. Diphenhydramine was the most effective inhibitor of edema and increased vascular permeability induced by the venom. Injection of the venom i.p. caused exocytosis and degranulation of mesentery mast cells with a decreased electron density of released granules. Systemic administration of diphenhydramine inhibited the venom-induced exocytosis. Diphenhydramine and pyrilamine inhibited the contraction of guinea-pig ileum caused by venom or compound 48/80. It is concluded that histamine released from mast cells plays an important role in the causation of the edema induced by Trimeresurus mucrosquamatus snakebites.