Increased cytochrome P-450 activity in Aspergillus fumigatus after xenobiotic exposure

Microsomal fractions were isolated from Aspergillus fumigatus cultures that had been treated with dimethylsulphoxide (DMSO), ethanol, benzopyrene, phenobarbital or naphthalene. All these xenobiotics increased microsomal cytochrome P-450 content. Cytochrome P-450 reductase activity remained unaffected and no alteration in the microsomal protein profile was detectable by SDS PAGE. Benzopyrene, dimethylaniline, hexobarbitol and p-nitroanisole were metabolised by A. fumigatus microsomes, while aniline, ethoxyresorufin and pentoxyresorufin were not. No xenobiotic elicited a more specific oxidation of any of the substrates. A. fumigatus microsomes also catalyzed the cell-free biosynthesis of ergosterol and quantitative analysis of assay metabolites showed that exposure to ethanol, benzopyrene or phenobarbitone in vivo resulted in enhanced ergosterol biosynthesis in vitro.