Influence of environmental temperature on the induction of xenobiotic metabolism by β-naphthoflavone in rainbow trout, Salmo gairdneri

Abstract

The response of hepatic microsomal cytochrome P-450 monooxygenase and UDPglucuronosyltransferase to a common inducer, β-naphthoflavone, was investigated in rainbow trout acclimated to 5 or 17°C. The hepatic microsomal 7-ethoxycoumarin- O-deethylase, 7-ethoxyresorufin- O-deethylase, and benzo[ a]pyrene hydroxylase activities, measured at 5 or 17°C, were induced at both acclimation temperatures. Maximum response of 7-ethoxyresorufin- O-deethylase and 7-ethoxycoumarin- O-deethylase activities to β-naphthoflavone was obtained with doses of 5 mg/kg and above, both in warm- and cold-acclimated trout. In warm-acclimated trout the maximum degree of induction of cytochrome P-450-dependent activities was already evident on the day following treatment with β-naphthoflavone (100 mg/kg), whereas these activities reached maximum values after 3 days in cold-acclimated fish. Furthermore, the maximum induced values of 7-ethoxyresorufin- O-deethylase and benzo[ a]pyrene hydroxylase activities were higher in cold-acclimated than in warm-acclimated fish. β-Napthoflavone treatment caused a slight but significant increase (1.6-fold) in UDPglucuronosyltransferase activity in warm-acclimated fish when measured at 5 or 17°C, whereas in cold-acclimated fish a significant elevation was seen only when the activity was determined at environmental temperature (5°C).