The effects of drugs on erythrocytes in vitro: Heinz body formation, glutathione peroxidase inhibition and changes in mechanical fragility.

1 The relationship between mechanical fragility, glutathione peroxidase inhibition and Heinz body formation, in erythrocytes exposed to oxidant drugs in vitro, has been investigated. All drugs tested caused Heinz body formation, and with the exception of acetyl salicylic acid and salicylic acid, also caused increased erythrocyte mechanical fragility. 2 There was a direct relationship between mechanical fragility and drug concentration. Mechanical fragility increased in parallel with Heinz body formation, with primaquine, gentisic acid, ascorbic acid and potassium chlorate. In contrast Heinz body formation occurred at drug concentrations which did not cause a marked increase in mechanical fragility in the case of menadione, acetyl phenylhydrazine and phenylhydrazine. 3 The degree of inhibition of glutathione peroxidase was directly related to increased mechanical fragility with menadione, gentisic acid and potassium chlorate. However other substances causing increased mechanical fragility resulted in little or no loss of glutathione peroxidase activity. 4 The results show that there is no constant relationship between mechanical fragility caused by drugs, the formation of Heinz bodies and the inhibition of glutathione peroxidase. The factors contributing to oxidant drug-induced haemolysis appear to be variable and depend upon the drug concerned.