Cyanide stimulation of tri‐N‐butyltin mediated hemolysis

Abstract The effects of tributyltin and sodium cyanide on hemolysis in human erythrocytes are described. Tributyltin has a sharp cut‐off concentration for induction of hemolysis. A 5 μ M concentration of tributyltin induces hemolysis and 1 μ M or less does not in erythrocyte supensions with 2.3×10 8 cells per ml. The kinetics for tributyltin‐induced hemolysis are sigmoidal indicating a complex molecular mechanism leading to lysis. Ten m M sodium cyanide plus 1 μ M tributyltin does not stimulate hemolysis rates above levels observed with 10 m M sodium cyanide alone. Five m M sodium cyanide plus hemolytic concentrations of tributyltin stimulates hemolysis rates synergistically compared with either cyanide or tributyltin alone. Ultrastructurally, hemolytic concentrations of tributyltin can be visualized in the electron microscope by osmium staining during fixation as electron‐dense spheres penetrating the lipid bilayer of the erythrocyte plasma membrane. Ten m M sodium cyanide plus 25 μ M tributyltin increases slightly the size of osmiophilic structures in erythrocyte membranes compared with those spheres seen in cells exposed to 25 μ M tributyltin alone. Sodium cyanide is the only compound tested that stimulates tributyltin‐induced hemolysis. Sodium thiocynate, previously shown to be rapidly exchanged across erythrocyte membranes by tributyltin, reduces the rate of hemolysis. It is likely that sodium cyanide stimulates hemolysis in the presence of hemolytic tributyltin concentrations because the multimolecular, membrane‐intercalated, tributytin aggregates are transporting cyanide anion by the electrically silent, anion exchange mechanism demonstrated for other anions. It is suggested that this mechanism delivers cyanide anion to or near critical membrane sites where it is available for enzyme inhibition or cross‐linking of protein sulfhydryl groups.