ACTIVITIES OF POLLUTANT METABOLIZING AND DETOXICATION SYSTEMS IN THE LIVER OF THE PLAICE, PLEURONECTES-PLATESSA - SEX AND SEASONAL-VARIATIONS IN NONINDUCED FISH

1. The ability of immature plaice to perform a number of representative hepatic phase I and II biotransformations was examined. 2. Activities attributable to cytochrome P-450 1A1 and phenol UDP-glucuronosyltransferase activity were markedly higher in plaice than other fish or rats. Glucuronidation of sex hormones and bilirubin, conjugation of ethacrynic acid with glutathione and the sulphation of phenols was very much lower in plaice than in rats, indicating that these are minor pathways in this fish. 3. MFO activities in sexually mature female plaice were 20-25% of those in immature fish, whilst there were no significant differences in glutathione S-transferase or glutathione peroxidase activity. 4. Seasonal variations in activities were determined for use in biomonitoring studies. With the exception of microsomal GST, all enzymes and the liver somatic index showed a marked seasonal variation, activities were lower in summer and showed a gradual rise in autumn and winter with a peak in spring. This pattern appeared to be the inverse of the environmental temperature, indicative of a possible temperature-dependent effect; however, there was not direct proportionality and photoperiod, feeding behaviour, plasma corticosteroid and plasma glucose also show a similar cyclical variation. 5. Cytochrome P-450 dependent ethoxyresorufin O-deethylase and cytosolic glutathione S-transferase activities in immature male fish showed a two-fold elevation over those in immature females during late winter and spring in the period when gonadal regression might be occurring and may be due to elevated 11-ketotestosterone levels. © 1990.