POLYMORPHISM IN THE GLUTATHIONE CONJUGATION ACTIVITY OF HUMAN ERYTHROCYTES TOWARDS ETHYLENE DIBROMIDE AND 1,2-EPOXY-3-(P-NITROPHENOXY)-PROPANE

In this study a polymorphism in the conjugating activity of human erythrocyte cytosol towards the dihaloethane, ethylene dibromide (EDB; 1,2-dibromoethane) was found. Two out of 12 human erythrocyte cytosols did not catalyze the formation of glutathione (GSH) conjugates of [1,2-C-14]EDB. Ten cytosols formed the S,S'-ethylenebis(GSH) conjugate at a rate ranging from 0.5 to 3.2 (mean 1.76+/-0.95) pmol min(-1)(mg protein)(-1). The activity of the cytosols towards EDB was compared with the activity towards 1,2-epoxy-3-(p-nitrophenoxy)-propane (EPNP) and 1-chloro-2,4-dinitrobenzene (CDNB). The GSH conjugates formed from EDB, EPNP and CDNB were all quantified by HPLC. Every cytosol was active with the classical GST substrate CDNB (2.04+/-0.74 nmol min(-1) (mg protein)(-1)). The two samples not showing any detectable activity towards EDB were also inactive towards EPNP: The activity towards EDB correlated significantly with EPNP (r(s) = 0.90, P < 0.005; Spearman's rank correlation), but not with CDNB (r(s) = 0.36, P > 0.10). In the incubations with EPNP, the alpha-, mu-, and pi-class glutathione S-transferase (GST) inhibitor S-hexyl(GSH) was included, indicating that the class-theta GST is the principal GST class conjugating EDB in erythrocyte cytosol. The apparent polymorphism of GST-theta which has recently been recognized to be crucial for several mono- and dihalomethanes, will thus also have considerable implications for the risk assessment of EDB.