Evidence for carriage of silver by sulphadimidine: haemolysis of human erythrocytes.

1 Human erythrocytes suspended in isotonic saline haemolyse in the presence of both Ag+ ions and sulphadimidine. 2 Neither Ag+ ions nor sulphadimidine on their own will haemolyse erythrocytes suspended in isotonic saline. 3 At constant Ag+ ion concentration the degree of haemolysis of saline-suspended erythrocytes depends upon the concentration of sulphadimidine. 4 Human erythrocytes suspended in isotonic sucrose (chloride-free) haemolyse in the presence of Ag+ ions. 5 Sulphadimidine in chloride-free sucrose competes with erythrocytes for Ag+ ions resulting in stoichiometric protection of the erythrocytes from the haemolytic action of Ag+ ions. 6 Haemolysis occurs when each erythrocyte receives approximately 1.2 X 10(9) Ag+ ions whether suspended in saline or sucrose. 7 Sulphadimidine acts as a carrier for Ag+ ions and so prevents their precipitation as AgCl when erythrocytes are suspended in saline.