EFFECT OF METHIDATHION ON THE CYTOCHROME-P-450 1A IN THE CYPRINID FISH GUDGEON (GOBIO-GOBIO)

Effect of methidathion (organophosphate) on the P-450 1A induction was assessed both by measurements of the induction of the EROD activity a nd of the immunodetection of the CYP1A protein in gudgeon. Fish were p re-treated with 5 mg kg(-1) of beta-naphthoflavone (BNF) and exposed t o environmental concentrations of methidathion in laboratory. Methidat hion proved to inhibit EROD induction in vivo and in vitro. In contras t, levels of immunoquantified CYP1A were found to be slightly higher i n microsomes from fish exposed to 10-30 mu g l(-1) of methidathion tha n in control fish exposed to BNF alone. This suggests that the inhibit ion of the EROD activity by methidathion resulted from a catalytic inh ibition without decrease of the CYP1A protein. (C) 1998 Elsevier Scien ce B.V. All rights reserved.