Mixed Function Oxidases in an Australian Marsupial, the Brushtail Possum (Trichosurus vulpecula)

Investigation of the mixed function oxidase system of the brushtail possum was undertaken to provide fundamental information about this detoxication enzyme system in a marsupial. Brushtail possum hepatic cytochrome P450, cytochrome b5 and NADPH-cytochrome c reductase levels, 7-ethoxyresorufin O-deethylase and (EROD) 7-ethoxycoumarin O-deethylase (ECOD) activities were in the range of values reported for eutherian mammals. Hepatic cyrochrome P450 content was significantly greater (p < 0.01) in brushtail possums from a non-urban population in comparison to an urban population, as was ECOD activity (p < 0.0001). EROD activity was significantly greater in female brushtail possums in comparison to males (p < 0.01). The factors potentially influencing the population- and sex-specific expression of cytochrome P450 isoenzymes in the brushtail possum are discussed and include exogenous dietary xenobiotics and endogenous hormonal alterations influenced by reproductive status.