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

Venom (10 mu g/ml) relaxed phenylephrine-precontracted aortae. This relaxation was unaffected by removal of the endothelium or a combination of N-G-nitro-L-arginine (LNOARG; 0.1 mM), oxyhaemoglobin (10 mu M) and indomethacin (10 mu M). 4-BPB (0.78 mM), propranolol (1 mu M), or a combination of apamin (0.1 mu M), charybdotoxin (0.1 mu M) and glibenclamide (10 mu M) did not effect endothelium-independent relaxation, suggesting a lack of PLA(2) activity or an effect at beta-adrenoceptors or K+ channels. Venom (10 mu g/ml) reversed Bay K 8644 (0.1 mu M)-induced contraction indicating the venom may have an effect on L-type Ca2+ channels. (C) 1998 Elsevier Science Ltd. All rights reserved.