Seasonal hepatic cytochrome P-450 induction in cotton rats (Sigmodon hispidus) inhabiting petrochemical waste sites

Wildlife species inhabiting contaminated sites are often exposed to complex mixtures of chemicals that have known effects on physiological and biochemical function. We evaluated the induction of major hepatic cytochrome P-450 isoenzymes through O-dealkylation of various resorufin ethers in wild cotton rats (Sigmodon hispidus) inhabiting three reference areas and three contaminated areas at an abandoned oil refinery Superfund waste site in Oklahoma. Isoenzyme activities were monitored in animals from these sites in summer and winter for 2 years. O-dealkylation of ethoxyresorufin and methoxyresorufin was significantly greater (170–180%) in cotton rats from contaminated areas compared to those from reference areas in summer, but not winter. These results indicate that the cotton rat may be a sensitive model species for biomonitoring petrochemical-contaminated ecosystems and demonstrate the importance of multi-season sampling in biomonitoring studies.