Effects of divalent cations on snake venom cardiotoxin-induced hemolysis and 3H-deoxyglucose-6-phosphate release from human red blood cells

Abstract

Ming-Shi Jiang, J. E. Fletcher and L. A. Smith. Effects of divalent cations on snake venom cardiotoxin-induced hemolysis and 3H-deoxyglucose-6-phosphate release from human red blood cells. Toxicon 27, 1297–1305, 1989.—At a low concentration of Naja naja kaouthia cardiotoxin (3 μM) Ca 2+, Sr 2+ and Ba 2+ (2 mM), had little to no effect on 3H-deoxyglucose-6-phosphate ( 3H-dGlu-6-p) or hemoglobin release. At higher concentrations of N. n. kaouthia cardiotoxin (≥ 10 μM), Ca 2+ (2 mM), but not Sr 2+ or Ba 2+, significantly enhanced 3H-dGlu-6-p and hemoglobin release. Mn 2+ (2 mM) almost completely inhibited 3H-dGlu-6-p release and hemolysis at both the 3 μM and 10 μM concentrations of cardiotoxin. At a fixed concentration of N. n. kaouthia cardiotoxin (3 μM), Ca 2+ at low concentrations (0.5 mM) enhanced 3H-dGlu-6-p and hemoglobin release, but at higher concentrations caused a dose-dependent inhibition of cardiotoxin action. The cardiotoxin from N. n. kaouthia venom (3 μM) induced 3H-dGlu-6-p release and hemolysis release with similar time courses and to similar extents. 3H-dGlu-6-p release induced by cardiotoxin was greatly enhanced as the pH of the medium was increased from 7.0 to 8.5. Similarities between 3H-dGlu-6-p and hemoglobin release do not support opening of pores in the plasmalemma of all red blood cells as the mode of action of cardiotoxins, but suggests that complete lysis of a subpopulation of cells occurs. Cardiotoxins have two components of lysis, only one of which is Ca 2+-dependent. The Ca 2+-dependent lysis is only evident at higher cardiotoxin concentrations and is likely due to trace phospholipase A 2 contamination in the toxin fraction. Mn 2+ is an effective antagonist of cardiotoxin action.