POLYMORPHISM OF GLUTATHIONE CONJUGATION OF METHYL-BROMIDE, ETHYLENE-OXIDE AND DICHLOROMETHANE IN HUMAN BLOOD - INFLUENCE ON THE INDUCTION OF SISTER CHROMATID EXCHANGES (SCE) IN LYMPHOCYTES

A hitherto unknown glutathione-S-transferase in human erythrocytes dis plays polymorphism: three quarters of the population (''conjugators'') possess, whereas one quarter (''non-conjugators'') lack this specific activity. A standard method for the identification of conjugators and non-conjugators with the use of methyl bromide and gas chromatography (head space technique) is described. Three substrates of the polymorp hic enzyme, methyl bromide, ethylene oxide and dichloromethane (methyl ene chloride), were incubated in vitro with individual whole blood sam ples of conjugators and non-conjugators. All three substances led to a marked increase of sister chromatid exchanges (SCE) in the lymphocyte s of the non-conjugators but not in those of conjugators. A protective effect of the glutathione-S-transferase activity in human erythrocyte s for the cytogenetic toxicity of these chemicals in vitro is thus con firmed. Since the enzyme activity is not found in erythrocytes of labo ratory animals, species extrapolations for risk assessment of methyl b romide, ethylene oxide and dichloromethane should be reconsidered.