Correlated biomarker responses for DNA damage and innate immunity revealed in a comparison between field and laboratory studies: Fathead Minnow Exposed to Tritium

International audienceTritium entering the aquatic environment contributes to the doses received by aquatic organisms. Multiple stressors inherent in natural environments, however, confound estimates for radio-sensitivity determined in controlled laboratory settings. To disentangle differences between field and laboratory outcomes, a multivariate analysis of biomarkers is described for fathead minnows (Pimephales promelas) exposed to tritium for 60 days and allowed to depurate for 60 days. In the laboratory study, the biomarkers for DNA damage and innate immunity display a dose-response relationship to internalized tritium. At the same tritium activity concentrations, the biomarkers for genotoxicity from the field study were lower than those from the laboratory study. This finding does not support an increase in genotoxic stress or sensitivity in the field-exposed fish, as was suggested by a meta-analysis comparing field data for radiation exposure from the Chernobyl exclusion zone and data from laboratory studies.In the laboratory, we see strong correlations between tritium exposure (up to 180 kBq/L), DNA damage (comet and micronuclei formation in gonad) and innate immune responses (phagocytosis and fluorescence associated with lysosomal membrane integrity in spleen). In the field, we see a high proportion of phagocytosis where the comet tail moment, but not the micronucleus frequency, correlated with fluorescence associated with lysosomal membrane integrity in spleen.The biomarkers for oxidative stress (catalase and superoxide dismutase) were specific to each study location with higher liver catalase activity in the laboratory exposures and higher superoxide dismutase in the field exposures. Indicators of overall health were not different between exposures, locations, or weight, length and organ somatic indices. This comparison highlights the relevance for using the DNA damages and innate immune system response endpoints as biomarkers of chronic low-dose tritium exposure, and the need to obtain a better mechanistic understanding of initiating events for the immune response