Electrophysiological and hemolytic activity elicited by the venom of the jellyfish Cassiopea xamachana

In this study, we determined hemolysis activity in human and sheep erythroc ytes, and characterized the electrical responses in Xenopus oocyte membrane elicited by the venom of the jellyfrsh Cassiopea xamachana (Cx). The Cx ve nom produced hemolysis in both species, being more potent on human red cell s. The electrophysiological study showed that the Cx venom elicited three d ifferent responses in the oocytes. One current was generated in all the ooc ytes tested and corresponded with a slow inward current (I-Cx) associated w ith an increase in membrane conductance. I-Cx was concentration-dependent a nd had a reversal potential of - 10.3 +/- 0.4 mV. Ionic substitution studie s indicated that the conductive pathway was mainly permeable to cations and non-selective. The oocyte membrane resistance was completely recovered aft er washout of the venom, this suggested that the effect was due to generati on of a specific membrane conductance as opposed to a possible non-specific membrane breakdown. A comparative study with three distinct native cationi c channels present in the oocyte membrane [i.e. (1) hemi-gap-junction chann els, (2) mechanosensitive channels, and (3) the ouabain-sensitive channel a ctivated by palytoxin], showed that I-Cx might correspond to opening of mec hanosensitive channels or to activation of an unknown cationic channel loca ted in the oocyte membrane. The bioactive fraction eliciting I-Cx were pept ides and was separated from two other peptidic hemolytic fractions by chrom atography. (C) 2001 Elsevier Science Ltd. All rights reserved.