Hepatic glutathione-S-transferase activity of mastomys and other rodents toward aflatoxin B₁ epoxide

Abstract

Objectives: To study the liver glutathione S-transferase (GST) activity toward aflatoxin B₁ (AFB₁) exo-epoxide in mastomys in comparison with rat, mouse and hamster, we performed in vitro studies of the liver enzymes activity. Materials and Methods: AFB₁ metabolism by liver microsomes including formation of AFB1-DNA adducts was studied using [³H] AFB₁. The liver cytosolic GST activity of mastomys and other rodents toward AFB₁-exo-epoxide were measured using HPLC with chiral column. Results. Cytosolic GST activity toward AFB₁-exo-epoxide was highest in mastomys liver, and higher in the hamster and mouse livers than in the rat liver, correlating well with the differences of the sensitivity of a given species to the toxicity of AFB₁. However, no relationship was noted between the sensitivity of a given species to the toxicity of AFB₁ and the microsomal activity of binding of AFB₁ to DNA or metabolizing AFB₁ to AFM₁, AFQ₁, and AFP₁. The importance of GST mediated AFB₁-exo-epoxide conjugation with glutathione in ditermining the differing sensitivities of these species to AFB₁ toxicity was demonstrated. The extremely high activity of GST in mastomys seems to be related to the tolerance to AFB₁ toxicity and indicates that this species would be a good model animal for studying the relationship between hepatic GST activity and AFB₁ toxicity.