THE EFFECT OF THERMAL-ACCLIMATION ON THE ACTIVITY OF ARYLHYDROCARBON HYDROXYLASE IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

1. The possibility that temperature acclimation (to 10 or 18-degrees-C for 28 days) would alter the cytochromes P-450 of rainbow trout was addressed. 2. The specific content of LM4b (P-450 IA1), the trout isozyme responsible for activation of polynuclear aromatic hydrocarbons, was lower in 18-degrees-C fish than it was in 10-degrees-C fish. 3. Kinetic analysis of aryl hydrocarbon hydroxylase indicated that, while thermal acclimation caused no change in V(max), it lowered the apparent K(m) of this enzyme for benzo[a]pyrene when assayed at acutely shifted temperatures. 4. Thermal acclimation of fish may have significance when feral populations are subjected to acute temperature shifts.