EXPRESSION OF MULTIXENOBIOTIC RESISTANCE MECHANISM IN A MARINE MUSSELMYTILUS-GALLOPROVINCIALIS AS A BIOMARKER OF EXPOSURE TO POLLUTED ENVIRONMENTS

The gills of mussel Mytilus galloprovincialis express a multixenobioti c resistance mechanism (MXRM) mediated by P-glycoprotein activity, as evidenced by the rate of (G-H-3)vincristine accumulation and its sensi tivity to verapamil, as well as by the direct immunochemical detection of P-glycoprotein by Western blotting analysis. The MXRM is induced a t polluted sites: gills from mussels living at polluted sites accumula te less vincristine, the vincristine accumulation is less sensitive to verapamil, and in most cases express higher levels of P-glycoprotein. The state of induction of functional activity of MXRM is proportional to the level of pollution, as demonstrated at sites along the well de fined pollution gradient in the aquatorium of Rovinj, Northern Adriati c. Since the immunological expression of P-glycoprotein may be comprom ised by high interindividual differences, season, and some as yet unkn own factors, it could not be used as a single marker of exposure. Howe ver, the rate of vincristine accumulation and its sensitivity to verap amil offer a new, informatively powerful, molecular biomarker of expos ure.