ALTERATIONS IN IMMUNE PARAMETERS ASSOCIATED WITH LOW-LEVEL METHYLMERCURY EXPOSURE IN MICE

Methylmercury (MeHg) is a known toxicant and continues to be a signifi cant environmental contaminant. While the neurotoxicity and developmen tal toxicity of MeHg are well established, the immunotoxic effects of MeHg are just now being studied and described. This study evaluated st rain and gender specific effects of low level, prolonged MeHg exposure in mice. Mice were exposed to MeHg in the drinking water (0, 3 or 10 ppm) for 4 weeks. Splenocytes and thymocytes were evaluated for altera tions in immunophenotype, GSH levels, and intracellular Ca2+ flux afte r mitogen stimulation. MeHg exposure resulted in alterations in spleno cyte and thymocyte subsets and a dose dependent decrease in GSH levels (as measured by monochlorobimane fluorescence and flow cytometry) of all splenocyte subsets. This decrease in GSH was further confirmed by biochemical assay in splenocytes. In addition, there was a dose respon se related decrease in mitogen stimulated Ca2+ flux and in the percent ages of CD4+ splenocytes and CD8+ splenocytes from mice exposed to 10 ppm of MeHg. These results suggest that low-level chronic MeHg exposur e may cause immune disfunction by disturbing thiol redox balance, tran smembrane signaling and splenic cellularity.