Conjugation of microsome generated and synthetic aflatoxin B1-8,9 epoxide and styrene oxide to glutathione by purified glutathione S-transferases from hamster and mouse livers.

ABSTRACT

Glutathione (GSH) conjugation of microsome-mediated and synthetic aflatoxin B1 (AFB1)-epoxide and styrene oxide has been studied with purified glutathione transferases (GSTs) from mouse and hamster liver cytosols. In hamster, with microsomally activated epoxide, the alpha group of GSTs show about 10-fold more activity than the mu group. With the synthetic AFB1 epoxide, the mu enzymes designated H3B and C show considerable activity although less than alpha, whereas H3A and D demonstrate similar ranges of activity as the alpha group. The pi class of GST could not be assayed due to its absence in the hamster liver. The mouse liver cytosols show 3.6-fold greater activity than hamster cytosol in microsome mediated assay system. The mouse alpha and mu enzymes have similar levels of activity in the microsome mediated system; this activity could not be determined with the pi GST due to shortage of this enzyme. The alpha group has 2- and 5-fold higher activity than mu and pi group of GSTs, respectively, with the synthetic epoxide of AFB1. With styrene oxide, the purified GSTs from hamster liver show total loss of activity whereas in the mouse alpha, mu and pi classes of GSTs have similar range of activity as the cytosol. The role of alpha and mu isozymes of GST in rendering these animals resistant to hepatocarcinogenecity is suggested.