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PM11 Wildlife Ecotoxicology
(PM193) Exposure to methylmercury (MeHg) in vitro alters lymphocyte proliferation in loggerhead turtles and bottlenose dolphin blood leukocytes.
Hessemann, L1, Day, R2, Christopher, S2, Arendt, M3, Maier, P3, Segars, A3, Whitaker, J3, Bossart, G4, Fair, P1, 5, Peden-Adams, M1, 1 Marine Biomedicine and Environmental Science Center, Medical University of South Carolina, Charleston, SC, USA2 National Institute of Standards and Technology, Hollings Marine Laboratory, Charleston, SC, USA3 South Carolina Department of Natural Resources, Marine Resources Division, Charleston, SC, USA4 Harbor Branch Oceanographic Institute, Ft. Pierce, FL, USA5 NOAA/NOS/CCEHBR, Charleston, SC, USA
ABSTRACT- Mercury (Hg) is a naturally occurring element found in the earths crust. However, its environmental distribution has increased since the industrial revolution from anthropogenic sources. Elemental mercury is converted to methymercury (MeHg) by bacteria through a non-enzymatic transfer of a methyl group to the Hg. In surface water, MeHg is bioaccumulated and biomagnified in aquatic animals through the food chain. Mercurial compunds are know to be immunotoxic having varied effects related to exposure levels including both immunostimulation and immunosuppression. Mercury exposures in rodents decreases macrophage cytokine production, modulates NK cell activity, promotes inflammatory reactions, increases lysozyme activity and susceptibility to viruses (i.e.: Herpes simplex II), modulates lymphocyte proliferation, and induces autoimmune disease. This study, therefore, determined the effects of mercury on immune function in two protected aquatic species: the loggerhead sea turtle and the bottlenose dolphin. Leukocytes were collected from fresh non-lethal blood samples taken during permitted live captures during the summer of 2003. Dose-responsive effects on T- and B-cell proliferation were assessed using the mitogen-induced lymphocyte proliferation assays that have been optimized by this lab for these species. MeHg was diluted in purified, sterile tissue culture water and concentrations examined included 0, 0.01, 0.03, 0.05, 0.1, 0.3, 0.5, and 1 ppm. Cell viability was verified by trypan blue exclusion. Dose-responsive effects were seen in both species resulting in suppression of lymphocyte proliferation. No and low observed effect levels varied with species and mitogen used. Concentrations of MeHg used were not directly toxic to the cells, as cell viability was not effected. These data indicate that similar responses are seen in vitro for both species at environmentally relevant concentrations and that the in vivo effects of mercury on immune function should be further studied in these species.
Key words: loggerhead sea turtle, mercury, bottlenose dolphin, immune function
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