TEMPORAL VARIATION OF CYP1A INDEXES, PCB AND 1-OH PYRENE CONCENTRATION IN FLOUNDER, PLATICHTHYS-FLESUS, FROM THE DUTCH WADDEN SEA

Two surveys were carried out to examine the temporal variation of hepa tic cytochrome P450 1A(CYP1A) indices and indices of exposure to organ ic contaminants in flounder, Platichthys flesus, in the Dutch Wadden S ea. Hepatic CYP1A protein was measured immunochemically using a semiqu antitative ELISA, and also by its catalytic activity using the 7-ethox yresorufin O-deethylation activity (EROD) assay. Concentrations of a s election of CB congeners in muscle and liver, and concentrations of 1- OH pyrene in bile, were used as indicators of exposure to PCBs and PAH s respectively. Both classes of compounds contain CYP1A-inducing conge ners. Muscle and liver concentrations of CB congeners remained stable between June and March. However, a distinct peak in concentrations occ urred just after the spawning period during March to April, but only i n mature males. This peak could be associated with the presence of a p opulation of migrating fish at the sampling location at that particula r time. The concentration of 1-OH pyrene in bile showed a very differe nt temporal pattern, with lowest concentrations just after the spawnin g period. CYP1A indices remained stable from June to October, but a di stinct peak occurred immediately after the spawning period. In adult f lounder, sex-related differences in EROD activity were observed during the spawning period, and sex-related differences in CYP1A protein lev el during the post-spawning period (March to June). The results of the present study indicate that spawning-related seasonal fluctuations in CYP1A indices and PCB concentrations in flounder are comparable to th ose observed in other fish species. Monitoring programmes incorporatin g the measurement of these parameters should take seasonal fluctuation s into account. Such programmes should preferably focus on the period June to October in order to minimise the influence of physiological pr ocesses and migratory behaviour associated with the annual reproductiv e cycle, If this is done, sampling does not need to take into account the sex, sexual maturity, or morphological state of the fish, although limiting the range of lengths incorporated in the sample to, say, 18 to 32 cm, will avoid excessive variation in fish age. Copyright (C) 19 96 Elsevier Science Ltd.