INTERACTION OF ENVIRONMENTAL XENOBIOTICS WITH A MULTIXENOBIOTIC DEFENSE-MECHANISM IN THE BAY MUSSEL MYTILUS-GALLOPROVINCIALIS FROM THE COAST OF CALIFORNIA

A multixenobiotic defense mechanism similar to a P-glycoprotein multid rug transporter was characterized in the gills of the mussel Mytilus g alloprovincialis from Monterey, California. Using a fluorescent dye as say, we measured multixenobiotic transport activity in individual gill cells and assessed the effects of inhibitors or competitive substrate s on activity. Natural products that inhibit the mammalian transporter also affected dye transport in the mussel gill. Four moderately hydro phobic pesticides (dacthal, chlorbenside, sulfallate, and pentachlorop henol) 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 gil ls, indicating their interaction with a multixenobiotic transport mech anism in this organism. The reactivity with these highly hydrophobic c ompounds seen in M. galloprovincialis differs from related transporter s found in other organisms. A protein in the gill cross-reacts with an tibodies directed against the mammalian multidrug transport protein. T he level of protein can be assessed easily by dot blot procedures and may facilitate quantitation of protein levels in field situations.