Seasonal variation of hepatic biotransformation in female and male rainbow trout ( Salmo gairdneri)

Abstract

1. 1. Seasonal and sex variations in the cytochrome P450 content and monooxygenase and glucuronidation activities were observed in the liver microsomes of rainbow trout cultivated in North-European waters. 2. 2. During the summer the specific monooxygenase activities lowered but the total calculated capacity remained unchanged (measured at 18°C) or increased (measured at environmental temperatures) due to liver growth. 3. 3. During water cooling in autumn the specific monooxygenase activity as well as the total capacity showed an ideal temperature compensation and remained unchanged if measured at environmental temperatures but increased considerably if measured at 18°C. 4. 4. Before the spawning time cytochrome P450 and the monooxygenase activities lowered in both sexes but more in females revealing a temporary sex difference which disappeared after spawning. 5. 5. The specific UDP glucuronosyltransferase activity lowered considerably during the cooling of environmental temperature, and thereafter an increase in both sexes was observed towards the spawning time (significantly higher in females) and coming summer.