Seasonal and sex-linked variations in hepatic and extrahepatic biotransformation activities in striped mullet (Mullus barbatus).

Microsomal cytochrome P450 content, NADPH-cytochrome c reductase, and phase I (ethoxycoumarin and ethoxyresorufin O-dealkylases) and phase II (glutathione S-transferase and UDP-glucuronyltransferase) activities were studied in the liver and intestine of the striped mullet (Mullus barbatus) for 8 months (before and during sexual maturation). Biotransformation activities were much lower in extrahepatic tissues than the corresponding activities in the liver. Intestinal and hepatic biotransformation activities presented similar seasonal fluctuations: Phase I activity increased from October to February (during water cooling) and generally decreased before spawning; Phase II activity was not greatly different. Moreover, NADPH-cytochrome c reductase, ethoxyresorufin O-dealkylase, and glutathione S-transferase activities were measured in the kidney during the sexual maturation period. Renal phase I and phase II activities showed very little fluctuation during the 5 months studied. Cytochrome P450 and ethoxycoumarin and ethoxyresorufin O-dealkylases exhibited sex-linked differences during sexual maturation, whatever the tissue: in the liver the values are higher in male fish, whereas in the intestine and kidney they are lower.