Induction of CYP2M1 and CYP2K1 lauric acid hydroxylase activities by peroxisome proliferating agents in certain fish species: Possible implications

In many higher vertebrates, species and gender-specific sensitivity to peroxisome proliferating agents (PPAs) and their toxic effects has been described. Sensitivity may correlate with the induction of lauric acid hydroxylase (LAH) activity. In rainbow trout (Oncorhynchus mykiss) LAH has been identified with at least two cytochromes P450, CYP2M1 and CYP2K1. Previously, bluegill (Lepomis macrochirus) and catfish (Ictalurus punctatus) had been shown to produce CYP2M1 and CYP2K1 immunoreactive protein induction upon treatment with PPAs. The current research extends that observation by demonstration of the associated lauric acid hydroxylase activities after exposure to PPAs. Male bluegill and catfish were treated using a single i.p. injection with olive oil vehicle or ciprofibrate (a model PPA; 100 mg kg−1) or clofibrate (less potent PPA) 48 h prior to microsome preparation. Olive oil-treated female catfish liver and kidney microsomes metabolize lauric acid to a greater extent than male microsomes (83 vs 40% and 77 vs 5%, respectively). Male bluegill liver and male catfish kidney exhibit significant induction of specific LAH after PPA treatment. These observations, taken together with previous work in mammals, may portend possible adverse consequences to sensitive fish species exposed to environmental chemical contamination by PPAs.