BIOACTIVITY AND MECHANISM OF ACTION OF LOPHOZOZYMUS PICTOR TOXIN

The bioactivity of Lophozozymus pictor toxin (LPTX) and the possible m echanism of action of the purified toxin are described. LPTX is found to possess palytoxin-like bioactivities. Besides exhibiting cytotoxic and haemolytic properties, LPTX causes the release of K+ from erythroc ytes and inhibits 2-[C-14]deoxy-D-glucose uptake into HeLa cells. Alth ough LPTX acts on HeLa cell and erythrocyte membranes, it does not int eract with mitochondrial or liposomal membranes containing different p hospholipid compositions. Ouabain, but not sphingomyelin, is able to p revent the toxic effects of LPTX. This antagonistic effect of ouabain on LPTX suggests that the toxin might mediate its toxic effects via th e membrane Na+/K+-ATPase but not through interaction with membrane lip ids.