Chloroform-induced alteration of glutathione s-transferase activity

Abstract

The effect of chloroform treatment on the hepatic glutathione S-transferases was studied in phenobarbital-treated rats. The apparent isozymic composition of glutathione S-transferases in hepatic cytosol was changed after chloroform treatment. Glutathione S-transferases AA, A, B, C, and D + E were observed in hepatic cytosol from untreated rats; in contrast, the catalytic activity associated with basic glutathione S-transferases, such as AA, A, B, and C, decreased with time after chloroform treatment. Glutathione S-transferase B was not detectable 2 hr after chloroform treatment, and glutathione S-transferases AA and C were scarcely detectable after 5 hr. Twenty-four hours after chloroform treatment, glutathione S-transferases A and C were clearly detectable as was D + E and a small amount of B. Hepatic cytosolic glutathione S-transferase activity was decreased by chloroform treatment, and reached a minimum at 5 hr after treatment. Corresponding to the decrease of hepatic cytosol glutathione S-transferase activity, serum glutathione S-transferase activity was elevated maximally 5 hr after chloroform treatment and returned to almost normal by 24 hr. Treatment of rats with SKF 525-A or cysteine inhibited the chloroform-induced elevation of serum glutathione S-transferase activity. The chromatographic properties of the gluathione S-transferases present in serum were similar to glutathione S-transferase D + E. Furthermore, after incubation of partially purified cytosolic glutathione S-transferases with chloroform in the presence of hepatic microsomes and NADPH, only transferase D + E was detected. The addition of bilirubin to partially purified cytosolic glutathione S-transferase decreased the basic character of glutathione S-transferases B and C. In conclusion, chloroform caused a release of hepatic cytosolic glutathione S-transferases into serum. Both the active metabolite of chloroform, which was produced by the microsomal cytochrome P-450 system, and bilirubin, which was increased by chloroform treatment, played roles in altering the properties of the glutathione S-transferases.