Expression of multixenobiotic resistance mechanism in a marine mussel Mytilus galloprovincialis as a biomarker of exposure to polluted environments

The gills of mussel Mytilus galloprovincialis express a multixenobiotic resistance mechanism (MXRM) mediated by P-glycoprotein activity, as evidenced by the rate of (G- 3H) vincristine accumulation and its sensitivity to verapamil, as well as by the direct immunochemical detection of P-glycoprotein by Western blotting analysis. The MXRM is induced at polluted sites: gills from mussels living at polluted sites accumulate 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 defined pollution gradient in the aquatorium of Rovinj, Northern Adriatic. Since the immunological expression of P-glycoprotein may be compromised by high interindividual differences, season, and some as yet unknown factors, it could not be used as a single marker of exposure. However, the rate of vincristine accumulation and its sensitivity to verapamil offer a new, informatively powerful, molecular biomarker of exposure.