Influence of gender, feeding regimen, and exposure duration on gene expression associated with xenobiotic metabolism in fathead minnows (Pimephales promelas)

Little is known about how gender and diet affect the metabolism of environmental contaminants in fish. This study was undertaken to compare these differences in hepatic mRNA expression of two genes associated with xenobiotic metabolism: the pregnane x-receptor (PXR) and cytochrome P450 3A4 (CYP3A4). PXR is an ideal receptor to study xenobiotic metabolism as it binds to a vast array of anthropogenic compounds and induces transcription of genes involved in metabolizing xenobiotic compounds, such as CYP3A4. In this study FHM were separated by gender and feeding regimen (fed versus unfed), and injected with control (corn oil), clotrimazole, or pregnene-16α-olone, and expression monitored after 2- and 5-days of treatment. Our research indicates that there are gender- and diet-specific differences in the expression of PXR and CYP3A4, the most striking of which was a significant increase in the expression of PXR and CYP3A4 in unfed females as compared to all other groups. Understanding the relationship among xenobiotic metabolism, gender and diet would be of particular interest in the study of contaminated habitats, where fish may have to adapt to reductions in food quantity or quality while being exposed to toxic compounds.