Hepatic biotransformation enzymes in aquaculture European sea bass (Dicentrarchus labrax): kinetic parameters and induction with benzo(A)pyrene

Abstract

1. 1. Phase I and phase II biotransformation enzyme activities, viz . I: NADPH-cytochrome c (P-450) reductase, 7-ethoxyresorufin O- deethylase (EROD), 7-ethoxycoumarin O- deethylase (ECOD) and benzo(a)pyrene monooxygenase (BaPMO); and II: uridine diphosphate glucuronyl transferase (UDPGT) and glutathione S- transferase (GST), were characterized in hepatic cytosol (GST) and microsomes of European sea bass ( Dicentrarchus labrax ) with respect to kinetic parameters ( K M and V m ) and linearity with time and protein concentration. 2. 2. Mean apparent K m values in μM for the xenobiotic substrates were 0.046 (EROD), 29 (ECOD), 9.93 (BaPMO), 67 ( p- nitrophenol , UDPGT) and 33 (1-chloro-2,4-dinitrobenzene, GST). 3. 3. Exposure to benzo(a)pyrene (i.p. 20 mg/kg, 14 hr optimal induction time) increased EROD, ECOD, BaPMO and UDPGT, but not GST, activities by, respectively, 3-, 2-, 2.5- and 3-fold. 4. 4. The results described in this paper show that European sea bass liver microsomes are able to hydroxylate the BaP (via BaPMO activity) and O- dealkylate 7-ethoxyresorufin as well as 7-ethoxycoumarin. Moreover, the presence of phase II enzymatic activities involved in the conversion of active intermediates to water-soluble compounds is shown. These different monooxygenase and phase II activities are induced by BaP and involved in compound metabolism in this species. 5. 5. The European sea bass, as an aquaculture species, offers potential for pollution biomonitoring, the numerous fish farms alongside coasts providing possible observation points.