Abstract
In order to gain a better understanding of the relative activities of glutathione S-transferase (GST) and aldehyde reductase toward aflatoxin B1 (AFB1) in relation to the variation of species susceptibilities, we studied the in vitro cytosolic GST and reductase activities in liver tissues from male Fischer rats, ICR mice and golden hamsters, adult male rainbow trouts and female piglets. The GST activity was determined by incubating the liver cytosol with glutathione (GSH) and AFB1 in the presence of the hamster liver microsomes to generate AFB1-8, 9-epoxide from AFB1. The reaction product, AFB1-GSH conjugate was quantified by HPLC with pirkele-concept chiral column using AFB1-GSH conjugate prepared by chemical reaction as standard. The reductase activity was determined by incubating liver cytosol with AFB1-dialdehyde, followed by the quantification of the metabolic product, AFB1-dialcohol, by HPLC. AFB1-dialcohol for HPLC was prepared by chemical reaction of AFB1-epoxide and N,N dimethylformamide standard. All the animal species possesed the GST activities and AFB1-GSH formed was increased with AFB1 concentration according to first order enzyme kinetics reaction. The Vmax and Km values of the GST activities in rodent species were higher and lower, respectively, than those in the trout and pig, being consistent with the relative susceptibilities to AFB1 of these animal species. However, no relationship was noted between the reductase activity and species susceptibility. Thus, the result of this study shows that GST toward AFB1, but not aldehyde reductase, is a determinant of the variation of species susceptibilities to AFB1.
