Isolation of a toxin from jellyfish Acromitus rabanchatu and its effect on skeletal muscle

A toxin (T-Ar) from the crude extract of jellyfish Acromitus rabanchatu was purified by (NH4)2SO4 fractionation followed by ion-exchange chromatography on DEAE-cellulose column. The mol. wt of T-Ar was found to be about 182,000. T-Ar reversibly blocked the twitch response of rat diaphragm muscle stimulated either indirectly or directly. It also reversibly blocked the twitch responses of chick biventer-cervicis muscle preparations. T-Ar failed to alter the contractures of the denervated rat diaphragm muscle preparation induced by acetylcholine, potassium chloride and caffeine. Similarly, acetylcholine and carbachol-induced contractures on chick biventer-cervicis muscle preparation were not influenced by T-Ar. The T-Ar-induced blockade of twitch responses of rat phrenic nerve-diaphragm was enhanced in high Na+ or low Ca2+ medium, and reduced in low Na+ or high Ca(2+)-containing medium. The results suggest that the toxin (T-Ar) possesses a direct paralysing effect on the muscle membrane.