Investigation of the multixenobiotic resistance mechanism in the freshwater fishes western mosquitofish, Gambusia affinis, and bluegill sunfish, Lepomis macrochirus.

The purpose of the study was to evaluate multixenobiotic resistance mechanism expression as a biomarker for contaminant exposure in freshwater fishes. Exposure to a known mammalian inhibitor (verapamil, 10 1M) and inducer (rhodamine 123, 3 1M) on the transport protein P-glycoprotein (Pgp) was investigated in the liver of the western mosquitofish and bluegill sunfish. No differences in the activity or expression of Pgp were measured in either species using a fluorometric accumulation assay and western blot analyses. The preliminary results from this study indicate that this detoxification mechanism may not be a sensitive indicator of contaminant exposure in certain teleost species.