MIXED-FUNCTION OXIDASES IN AN AUSTRALIAN MARSUPIAL, THE BRUSHTAIL POSSUM (TRICHOSURUS-VULPECULA)

Investigation of the mixed function oxidase system of the brushtail po ssum was undertaken to provide fundamental information about this deto xication enzyme system in a marsupial. Brushtail possum hepatic cytoch rome P450, cytochrome b(5) 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 m ammals. 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 activi ty was significantly greater in female brushtail possums in comparison to males (p < 0.01). The factors potentially influencing the populati on- and sex-specific expression of cytochrome P450 isoenzymes in the b rushtail possum are discussed and include exogenous dietary xenobiotic s and endogenous hormonal alterations influenced by reproductive statu s.