Abstract
Characteristics of the cardiovascular effects of habu venom were studied in vivo and in vitro in rats. Aortic pressure (AoP), heart rate (HR) and renal cortical blood flow (RCBF) assessed by a laser-Doppler flowmeter were measured in anesthetized rats. Administration of habu venom (0.2-1.6 mg/kg, i.v.) dose-dependently produced a fall in AoP without a marked change in HR. RCBF decreased significantly along with the decline in AoP. Heated habu venom (70°C for 5 min) or the residual venom by dialysis produced similar hemodynamic responses to nonheated crude habu venom. Although habu antivenin significantly reduced the effects of habu venom, indomethacin, aprotinin, atropine, captopril and chlorpheniramine did not. Methylprednisolone significantly attenuated these effects. Habu venom (10-5 to 3×10-4 g/ml) produced dose-dependent relaxations of the isolated rat aorta preparations precontracted with norepinephrine or KCl, which were not affected by indomethacin, nordihydroguaiaretic acid, p-bromophenacyl bromide, mepacrine, methylene blue or de-endothelialization. These results indicate that habu venom, particularly its heat-stable component(s) which has at least more than 10, 000 molecular weight, produces hypotensive and vasorelaxant effects in rats, and suggest that eicosanoids, kinins, histamine, ACh, and endothelium are scarcely involved in these effects.
