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 [1,2-14C]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 (rs = 0.90, P < 0.005; Spearman's rank correlation), but not with CDNB (rs = 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.
Ploemen
J H
JH
TNO Nutrition and Food Research Institute, Division of Toxicology, Zeist, The Netherlands.
Wormhoudt
L W
LW
van Ommen
B
B
Commandeur
J N
JN
Vermeulen
N P
NP
van Bladeren
P J
PJ
D002851:Chromatography, High Pressure Liquid; D003600:Cytosol / Q000378:metabolism; D004137:Dinitrochlorobenzene / Q000097:blood; D004852:Epoxy Compounds / Q000097:blood; D004912:Erythrocytes / Q000378:metabolism*; D015946:Ethylene Dibromide / Q000097:blood*; D005978:Glutathione / Q000097:blood*; D005982:Glutathione Transferase / Q000097:blood*; D006801:Humans; D007527:Isoenzymes / Q000097:blood*; D007700:Kinetics; D009596:Nitrophenols / Q000097:blood*; D011110:Polymorphism, Genetic
D004137:Dinitrochlorobenzene; D004852:Epoxy Compounds; D007527:Isoenzymes; D009596:Nitrophenols; D015946:Ethylene Dibromide; C007606:1,2-epoxy-3-(p-nitrophenoxy)propane; D005982:Glutathione Transferase; D005978:Glutathione