Mercury and Methylmercury Accumulation and Excretion in Prairie Voles (Microtus ochrogaster) Receiving Chronic Doses of Methylmercury

Methylmercury cation (MeHg) and divalent mercury (Hg⁺⁺) accumulation in liver, kidney, and brain were quantified in prairie voles (Microtus ochrogaster) at 0, 3, 6, and 12 weeks during chronic exposure to aqueous MeHg. Dose groups received deionized water or aqueous solutions containing 9, 103, or 920 ng MeHg/ml. Our study presents temporal patterns of Hg⁺⁺ and MeHg concentrations in organ tissues and makes inter-tissue comparisons at each time point to illustrate the accumulation and distribution of Hg species during the study. MeHg was accumulated in tissues for 3 weeks and then concentrations plateaued. Mercury accumulated in brain, liver, and kidney to average concentrations of 510 ng/g, 180 ng/g, and 3400 ng/g, respectively. MeHg and Hg⁺⁺ concentrations were roughly equivalent in liver, kidney, and urine. MeHg concentrations in brain tissue were 2 to 20 times the concentrations of Hg⁺⁺. Regression analysis was also used to demonstrate the utility of urinalysis as an indicator of Hg⁺⁺ and MeHg concentrations in organ tissue (p < 0.001).