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(274) Detection and accumulation of metallothionein mRNA by RT-PCR: Biomarker of metal contamination in mangrove oysters. Rebelo, Mauro1, Moraes, Milton2, da Silva, Hamilton3, Sampaio, Elisabeth2, Pfeiffer, Wolfgang1, 1 2 3 ABSTRACT- Metalothionein (MT) mRNA expression is directly correlated to levels of metal exposure in aquatic organisms. The use of reverse trasncriptase - polimerase chain reaction (RT-PCR) provided a reliable, specific and sensitive approach to determine mRNA accumulation in tissue samples of mangrove oysters (Crassostrea rhizophorae). MT and Key words: metallothionein, m RNA, oyster, rt-pcr |
Actin mRNA-specific primers were designed based on previously described sequences from C. virginica genes. Amplification of cDNA-derived mRNA defined MT and 
actin DNA fragments that demonstrated 94 and 92% of similarity with C. virginica genes respectively. The evaluation of MT mRNA detection in gills, guts, muscles and mantle samples from oysters collected in contaminated and control sites showed a different pattern of tissue expression. All tissue samples from contaminated oysters expressed MT mRNA. Differentially, for control tissues, only gills and mantle detectable levels of MT message. A quantitative approach based on RT-PCR was developed in order to perform the monitoring of impacted areas in vivo. Three sites at Sepetiba bay (Rio de Janeiro, Brasil) were sampled, as well as a control (uncontaminated) region and results show accumulation of MT-mRNA in oysters from contaminated sites are 50% higher than in control station. While whole body burdens metal concentrations are result of an integrative period of days or even months, MT-mRNA accumulation represents the response of hours or even minutes to metal contamination and thus provides efficient means to evaluate in situ rates of exposure and biovailability of heavy metals.