IDENTIFICATION OF PHOSPHOLIPASE A(2) AND NEUROTOXIC ACTIVITIES IN THEVENOM OF THE NEW GUINEAN SMALL-EYED SNAKE (MICROPECHIS-IKAHEKA)

S. L. Geh, A. Vincent, S. Rang, T. Abrahams, L. Jacobson, B. Lang and D. Warrell. Identification of phospholipase A(2) and neurotoxic activi ties in the venom of the New Guinean small-eyed snake (Micropechis ika heka). Toxicon 35, 101-109, 1997.-The Papua New Guinean small-eyed sna ke (Micropechis ikaheka) is recognised as a cause of life-threatening envenoming in certain parts of New Guinea. The clinical features sugge st the presence of toxins acting at the neuromuscular junction and on muscle. We have used the mouse phrenic nerve-hemidiaphragm preparation , a phospholipase A(2) assay, and I-125-neurotoxin-binding radioimmuno assays to look for toxic activities in the crude venom and in prelimin ary high-performance liquid chromatography(HPLC) fractions. Micropechi s ikaheka venom at 1 and 3 mu g/ml completely abolished nerve-evoked m uscle twitch within 70 min at 37 degrees C. There was also a sustained contracture of the muscle and some reduction in twitch tension evoked by direct stimulation; these were explained by the presence of phosph olipase A(2) activity. The venom inhibited the binding of I-125-alpha- bungarotoxin to detergent-extracted human muscle acetylcholine recepto r (AChR), and inhibited acetylcholine receptor function in a muscle ce ll line. It also inhibited binding of I-125-omega-conotoxin GVIA to de tergent-extracted human frontal cortex voltage-gated calcium channels, but this appeared to be dependent on the phospholipase A(2) activity. Identification of the main neurotoxic fractions following HPLC are sh own. Copyright (C) 1996 Elsevier Science Ltd.