Induction of monooxygenase activity in the intestine of spot (Leiostomus xanthurus), a marine teleost, by dietary polycyclic aromatic hydrocarbons.

The response of intestinal monooxygenases to dietary polycyclic aromatic hydrocarbon (PAH) exposure was evaluated in spot (Leiostomus xanthurus), a marine teleost fish. Ethoxyresorufin O-deethylase (EROD) and aryl hydrocarbon hydroxylase (AHH) activities were highest in the pyloric caeca and in the proximal half of the intestine. Intestinal microsomes from fish given control diets had very low levels of EROD and AHH activities relative to those in liver. After exposure to a diet containing 10 mg of 3-methylcholanthrene/kg of food, the levels of intestinal EROD and AHH activities increased 36-fold and 17-fold, respectively, such that intestinal monooxygenase activity exceeded that of the liver, which was not induced by this treatment. A significant increase in intestinal monooxygenase activity occurred in fish receiving dietary benzo[a]pyrene (BP) at concentrations as low as 10 micrograms of BP/kg food. A 5-fold increase in intestinal AHH and EROD activities was observed within 3 hr after administration of dietary BP. A plateau in gut monooxygenase activity occurred after approximately 3 days of PAH exposure; these activities decreased to control levels within 3 days after replacing the PAH diet with the control diet. Starvation resulted in disappearance of detectable monooxygenase activity. Monoclonal antibody (MAB 1-12-3) against the major PAH-inducible cytochrome P-450 (P-450E) in the liver of the marine teleost (Stenotomus chrysops) [Park et al. Arch. Biochem. Biophys. 249, 399 (1986)] recognized a single protein band in intestinal microsomes, with Mr near 54,000, which we conclude is the spot counterpart to cytochrome P-450E.(ABSTRACT TRUNCATED AT 250 WORDS)