Biotransformation enzymes and their induction by beta-naphthoflavone in adult sea bass (Dicentrarchus labrax)

In the present study we have determined for the first time the hepatic activities of several microsomal P-450 dependent monooxygenases including the testosterone hydroxylase and the Ah-receptor gene battery-related phase II enzymes [UDP-glucuronyl transferase (UDP-GT), DT-diaphorase, glutathione S-transferase, aldehyde dehydrogenases] in adult sea bass (300-400 g). We also investigated the effect of beta-naphtoflavone (beta-NF) on these enzymes to assess their potential as biomarkers of polycyclic aromatic hydrocarbon exposure. beta-NF. administered to fish with a single i.p. injection at various doses, resulted in an induction in the liver of the P-450 1A, as immunodetected by anti rat P-450 1A1 antibodies, P-450 1A-linked ethoxyresorufin-O-deethylase (EROD) and methoxyresorufin-O-demethylase (MEROD) activities. Among the phase II enzymes only the phenol UDP-GT was induced in liver by beta-NF. The time course of these inductions exhibited different patterns. EROD and MEROD activities reached a peak value 3 days post-injection and maintained values significantly above the corresponding control activities over the 30 days of the experiment, the phenol UDP-GT activity peaked at dap 8 and afterwards declined rapidly achieving the control value 18 days post-injection. A treatment of 80 mg kg(-1) beta-NF increased the immunodetectable P-450 1A apoprotein and EROD, but not MEROD, activity in extrahepatic tissues such as, gill, kidney and olfactory rosettes. Taken overall, the results indicate that MEROD. EROD and phenol UDP-GT activities may be useful biomarkers for the exposure of adult sea bass to polycyclic aromatic hydrocarbons. (C) 1998 Elsevier Science B.V. All rights reserved.