Changes in the activities of hepatic xenobiotic metabolizing enzymes after the administration of clenbuterol to female broilers.

Clenbuterol is a beta(2)-agonist drug which in some countries is used illegally to enhance the productivity of various food-producing species, including poultry. This work investigated whether the prolonged exposure of female broilers to clenbuterol modified the activity of hepatic microsomal or cytosolic enzyme systems concerned with the metabolism of drugs, pesticides, carcinogens and endogenous substrates such as sexual steroids. Clenbuterol was added to the birds' diet at concentrations of 1 or 25 ppm for 21 days. There was a dose-related decrease in the concentration of cytochrome P-450, and in the activities of the polycyclic aromatic hydrocarbon-inducible monooxygenases ethoxyresorufin O-de-ethylase and aryl hydrocarbon hydroxylase. The activities of glutathione S-transferase, N-acetyltransferase and uridinediphosphoglucuronyltransferase were not affected by the treatment