Neuromuscular action of Bothrops lanceolatus (Fer de lance) venom and a caseinolytic fraction

摘要

A protein capable of inducing neuromuscular blockade in avian preparations and of depolarizing mouse diaphragm muscle was isolated from Bothrops lanceolatus venom using gel filtration and ion-exchange chromatography. The purified protein was a single chain polypeptide with an estimated molecular mass of 27.5 kDa by SDS-PAGE and had caseinolytic activity (13.3 units/mg), but no phospholipase A(2). B. lanceolatus venom (50 mug/ml) and the caseinolytic protein (20 mug/ml) produced contracture and progressive irreversible blockade (50% in 25 +/- 5 min (SEM) and 45 +/- 15 min, respectively), in indirectly stimulated chick biventer cervicis preparations. The contractile responses to acetylcholine (ACh; 37 and 74 muM, n = 6) were inhibited by venom and the caseinolytic protein, whereas those to potassium (13.4 mM, n = 6) were not. Membrane resting potential measurements in mouse hemidiaphragm preparations showed that B. lanceolatus venom and the purified protein caused depolarization which was prevented by D-tubocurarine (14.6 mM). The venom produced a slight increase in the amplitude and frequency of miniature end-plate potentials, but this effect was not seen with the purified fraction. These results suggest that the purified protein acts exclusively post-synaptically. (C) 2002 Published by Elsevier Science Ltd. [References: 15]