EFFECT OF ALACHLOR ON HEPATIC CYTOCHROME P450 ENZYMES IN RATS

Alachlor ((2-chloro-N-methoxymethyl)-N-(2,6-diethylphenyl)acetamide) is a widely used preemergence herbicide which has been classified by the USEPA as a probable human carcinogen. The herbicide has been suggested to be metabolized by hepatic cytochrome P450 system. We examined the effects of alachlor on cytochrome P450 enzymes in rat liver microsomes. Rats were treated intraperitoneally with alachlor daily for 5 days, at doses of 25, 50 and 100 mg/kg. Among the cytochrome P450-dependent monooxygenase activities, 7-pentoxyresorufin O-depentylase, which is associated with CYP2B1, was dose-dependently increased by alachlor. The induction relative to control activity was 1.7–4.2-fold. The activities of CYP1A-dependent monooxygenases such as 7-ethoxyresorufin O-deethylase and acetanilide 4-hydroxylase were also significantly increased by alachlor at doses of 50 and 100 mg/kg (1.7–2.1-fold). Furthermore, immunoblotting showed that alachlor significantly increased CYP2B1/2 and CYP1A1/2 protein levels by 4.2–6.3-...