Pharmacological characterization of the rat paw edema induced by Bothrops lanceolatus (Fer de lance) venom

Abstract

The inflammatory response induced by Bothrops lanceolatus venom (BLV) in the rat hind-paw was studied measuring paw edema. Non-heated BLV (75 μg/paw) caused a marked paw edema accompanied by intense haemorrhage whereas heated venom (97°C, 30 s; 12.5–100 μg/paw) produced a dose- and time-dependent non-haemorrhagic edema. The response with heated BLV was maximal within 15 min disappearing over 24 h. Heated venom was then routinely used at the dose of 75 μg/paw. The prostacyclin analogue iloprost (0.1 μg/paw) potentiated by 125% the venom-induced edema. The histamine H 1 receptor antagonist mepyramine (6 mg/kg) or the serotonin/histamine receptor antagonist cyproheptadine (6 mg/kg) partially inhibited BLV-induced edema whereas the combination of both compounds virtually abolished the edema. The lipoxygenase inhibitor BWA4C (10 mg/kg), but not the cyclooxygenase inhibitor indomethacin (10 mg/kg), significantly inhibited the edema (35% reduction; P<0.05). Dexamethasone (1 mg/kg) also markedly ( P<0.001) reduced venom-induced edema. The bradykinin B 2 receptor antagonist Hoe 140 (0.6 mg/kg) reduced by 30% ( P<0.05) the venom induced edema, whereas the angiotensin-converting enzyme inhibitor captopril (300 μg/paw) potentiated by 42% ( P<0.05) the edema. Bothrops lanceolatus antivenon (anti-BLV) reduced by 28% ( P<0.05) the venom-induced edema while intravenous administration of antivenom failed to affect the edema. In conclusion, BLV-induced rat paw edema involves mast cell degranulation causing local release of histamine and serotonin, a phenomenon mediated mainly by kinins and lipoxygenase metabolites. Additionally, the use of a specific Bothrops lanceolatus antivenom, given subplantarily or intravenously, revealed to be little effective to prevent BLV-induced edema.