title: Changes in erythrocyte permeability due to palytoxin as compared to amphotericin B.
abstract: Palytoxin causes within minutes a temperature-dependent K+ loss from human and rat erythrocytes which is followed within hours by haemolysis. It decreases the osmotic resistance in a concentration-dependent manner, so that osmotic influences are negligible for K+ release but considerable in haemolysis. External K+ inhibits the haemoglobin release and Rb+ inhibits the release of K+ and haemoglobin. Ca2+ (over 20 microM) and borate (over 5 microM) enhance the loss of K+ and haemoglobin. With both Ca2+ and borate present, the efficacy of palytoxin is raised about 10 000-fold. Under these conditions, about 15 palytoxin molecules per human cell trigger a 50% K+ loss over a wide range of cell concentrations. The palytoxin effect is reversible. After depletion from K+ by low concentrations of palytoxin, human cells can be refilled with K+ and resealed. The pores formed by palytoxin are small. They allow the entrance of Na+ and choline, whereas inositol is largely excluded and Ca2+, as well as sucrose and inulin, are completely excluded. Amphotericin B resembles palytoxin in its ability to cause a considerable prelytic K+ loss and to form small pores. However, it is about 1000-times weaker than palytoxin, is not inhibited by K+ or Rb+, is not activated by Ca2+ or borate, and has a negative temperature dependence. Thus palytoxin represents a novel type of cytolysin.
mesh_terms: D000178:Acrylamides; D000666:Amphotericin B / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects*; D003064:Cnidarian Venoms / Q000494:pharmacology*; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D006461:Hemolysis; D006801:Humans; D007700:Kinetics; D009997:Osmotic Pressure; D011188:Potassium / Q000097:blood / Q000494:pharmacology; D051381:Rats; D012413:Rubidium / Q000494:pharmacology; D013696:Temperature; D000095702:Polyether Toxins
chemical_list: D000178:Acrylamides; D000666:Amphotericin B; D002118:Calcium; D003064:Cnidarian Venoms; D011188:Potassium; D012413:Rubidium; C010272:palytoxin; D000095702:Polyether Toxins