The modulation of protective effects of the multixenobiotic resistance mechanism in a clam Corbicula fluvinea

Recent evidence indicates that there is a multixenobiotic resistance mechanism (MXRM) in aquatic organisms which represents a general biological defense mechanism for protection against both endogenous and environmental toxicants. In aquatic organisms exposed to polluted waters, this mechanism is inducible. In this paper we show how the state of induction of MXRM in a clam Corbicula fluminea modulates the level of accumulation, or the level of toxic outcomes of exposure to vincristine or acetylaminofluorene (AAF), respectively. Induced clams, i.e. clams freshly collected at a polluted Rhine River site, or control clams exposed for 3 d either to water experimentally polluted with Diesel-2 oil or to Rhine River sediments, accumulated significantly less vincristine than control clams, i.e. clams held in aquaria for 6 weeks. Similarly, the number of single strand brakes (SSB) after AAF-exposure in DNA isolated from gills was significantly lower in induced clams in comparison with SSB found in control clams. Thus, clams may protect themselves from toxic effects by inducing their MXRM. This was supported by evidence that in the presence of staurosporine, the MXRM inhibitor, both found protections were reversed.