Interaction of environmental xenobiotics with a multixenobiotic defense mechanism in the bay mussel Mytilus galloprovincialis from the coast of California

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Abstract
A multixenobiotic defense mechanism similar to a P‐glycoprotein multidrug transporter was characterized in the gills of the mussel Mytilus galloprovincialis from Monterey, California. Using a fluorescent dye assay, we measured multixenobiotic transport activity in individual gill cells and assessed the effects of inhibitors or competitive substrates on activity. Natural products that inhibit the mammalian transporter also affected dye transport in the mussel gill. Four moderately hydrophobic pesticides (dacthal, chlorbenside, sulfallate, and pentachlorophenol) and four highly hydrophobic xenobiotics (p,p′‐DDT, p,p′‐DDD, p,p′‐DDE, and Aroclor 1254) all inhibited the efflux of dye from the gills, indicating their interaction with a multixenobiotic transport mechanism in this organism. The reactivity with these highly hydrophobic compounds seen in M. galloprovincialis differs from related transporters found in other organisms. A protein in the gill cross‐reacts with antibodies directed against the mammalian multidrug transport protein. The level of protein can be assessed easily by dot blot procedures and may facilitate quantitation of protein levels in field situations.