Dose-related induction of rat hepatic drug-metabolizing enzymes by diuron and chlorotoluron, two substituted phenylurea herbicides.

Dose-related induction of various hepatic drug-metabolizing enzymes has been investigated after short-term treatment of rats by diuron and chlorotoluron, a dichlorinated and a monochlorinated phenylurea herbicide, respectively. Results suggest that 'saturation' of the induction system of benzo(a)pyrene monooxygenase, 7-ethoxycoumarin O-deethylase and 7-ethoxyresorufin O-deethylase activities may occur in the same range of the molar doses of both compounds, and with the dichlorinated herbicide at much higher activities. Induction of epoxide hydrolase, UDP-glucuronyltransferase and glutathione S-transferases also shows saturation curves in the function of molar doses. However, the structural difference is not reflected in the enhancement of enzyme activities.