Differential effects of phenobarbitone on the hepatic and renal glutathione-S-transferases in the rhesus monkey

Objective: To comprehend the differential effects of phenobarbitone (PB) on the hepatic and renal glutathione-S-transferases (GSTs). Methods: Male rhesus monkeys were administered PB intraperitoneally at a dose of 50 mg/Kg body weight/day for four days. Livers and kidneys were homogenized and 100,000 x g supernatant were prepared. The assays of GSTs using 1-chloro- 2,4-dinitrobenzene (CDNB), 1,2-dichloro-4-nitrobenzene (DCNB) and ethacrynic acid (EA) were performed in the supernatant obtained from control and PB pretreated macaques. Results: PB caused a statistically significant decrease in the specific activity of hepatic GST towards CDNB (49%) and DCNB (64%) and a nonsignificant decrease towards EA (22%). In the kidney, the specific activities of GSTs towards these substrates were decreased by PB to a lesser extent (CDNB, 28%; DCNB, 11%; and EA, 18%) and were statistically nonsignificant. Conclusion: PB decreases the activity of hepatic GSTs significantly and that of renal GSTs nonsignificantly in the rhesus monkey. These observations are surprising in the context that PB is a well known inducer of GSTs in the rodents.