Kinetic analysis of glutathione transferase from rats exposed to sub-lethal and lethal concentrations of lead acetate

Abstract

The effects of lethal and sublethal doses of lead acetate on the induction and kinetic characteristics of glutathione transferase (GST) isozymes in rat liver and kidney were investigated. GST isozymes induction was monitored by the ability of the induced enzyme to conjugate glutathione (GSH) with model GST substrates. Liver isozymes were purified and separated into three main isoforms using ion-exchange chromatography and the kinetic characteristics in the absence and presence of the toxic metal ions examined. Lethal and sublethal doses of lead acetate resulted in different levels of GST induction in both liver and kidney depending on the substrates employed to assay for enzyme induction. Presence of 1 mM Sodium arsenate brought about changes in the kinetic parameters of the isozymes. We conclude that GST isozymes are induced in rats irrespective of the lead acetate dose that was administered and that in the presence of toxic metal ions, GST isozymes responded by altering their kinetics, permitting tight binding for substrates in some isozymes and loose binding in others.

Keywords: Glutathione transferase, Lead acetate, Induction, Kinetics.