A pharmacological examination of venoms from three species of death adder (Acanthophis antarcticus, Acanthophis praelongus and Acanthophis pyrrhus)

The common (A. antarcticus), northern (A. praelongus) and desert (A. pyrrhu s) death adders are species belonging to the Acanthophis genus. The present study compared some pharmacological aspects of the venoms of these species and examined the in vitro efficacy of death adder antivenom. Neurotoxicity was determined by the time to produce 90% inhibition (t(90)) of indirect ( 0.1 Hz, 0.2 ms, supramaximal voltage) twitches in the chick biventer cervic is nerve-muscle (3-10 mu g/ml) and mouse phrenic nerve-diaphragm (10 mu g/m l) preparations. A. praelongus venom was significantly less neurotoxic than A. antarcticus venom but was not significantly different From A. pyrrhus v enom. In the biventer muscle, all three venoms (3-10 mu g/ml) abolished res ponses to exogenous ACh (1 mM) and carbachol (20 mu M), but not KCl (40 mM) , indicating activity at post-synaptic nicotinic receptors. All venoms (30 mu g/ml) failed to produce significant inhibition of direct twitches (0.1 H z, 2.0 ms, supramaximal voltage) in the chick biventer cervicis nerve-muscl e preparation. However, A. praelongus (30 mu g/ml) venom initiated a signif icant direct contracture of muscle, indicative of some myotoxic activity. T he prior (10 min) administration of death adder antivenom (1 unit/ml), whic h is raised against A. antarcticus venom, markedly attenuated the twitch bl ockade produced by all venoms (10 mu g/ml). Administration of antivenom (1. 5 units/ml) at t(90) markedly reversed, over a period of 4 h, the inhibitio n of twitches produced by A. praelongus (3 mu g/ml, 72 +/- 6% recovery) and A. pyrrhus (3 mu g/ml, 51 +/- 9% recovery) but was less effective against A. antarcticus venom (3 mu g/ml, 22 +/- 7% recovery). These results suggest that all three venoms contain postsynaptic neurotoxins. Death adder antive nom displayed differing efficacy against the in vitro neurotoxicity of the three venoms. (C) 2000 Elsevier Science Ltd. All rights reserved.