The smooth muscle relaxant effects of venom from the inland taipan ( Oxyuranus microlepidotus)

Abstract

Venom (10 μg/ml) relaxed phenylephrine-precontracted aortae. This relaxation was unaffected by removal of the endothelium or a combination of N G-nitro- l-arginine ( l-NOARG; 0.1 mM), oxyhaemoglobin (10 μM) and indomethacin (10 μM). 4-BPB (0.78 mM), propranolol (1 μM), or a combination of apamin (0.1 μM), charybdotoxin (0.1 μM) and glibenclamide (10 μM) did not effect endothelium-independent relaxation, suggesting a lack of PLA 2 activity or an effect at β-adrenoceptors or K + channels. Venom (10 μg/ml) reversed Bay K 8644 (0.1 μM)-induced contraction indicating the venom may have an effect on l-type Ca 2+ channels.