LYMPHOCYTE PROLIFERATIVE RESPONSE AND TISSUE DISTRIBUTION OF METHYLMERCURY SULFIDE AND CHLORIDE IN EXPOSED RATS

The immunotoxic effects and tissue distribution of different forms of methylmercury compounds were studied in rats. Methylmercury sulfide or methylmercury chloride was fed to rats at concentrations of 5 or 500 mu g/L in drinking water for 8 wk. T-cell lymphocyte proliferative res ponse to phytohemagglutinin (PHA) and determination of tissue distribu tion of mercury by gas chromatography using electron capture were assa yed. Four different forms of mercury compounds were employed: MeHgS-, (MeHg)(2)S, (MeHg)(3)S+, and MeHgCl. Results indicated that exposure t o methylmercury significantly enhanced lymphocyte responsiveness in mo st of the exposed groups at the low concentration of 5 mu g/L, with th e highest proliferative response (fourfold increase) in the MeHgCl gro up. At 500 mu g/L, a significant decrease in the lymphocyte proliferat ive response was observed in the (MeHg)(3)S+ and MeHgCl groups; conver sely, the MeHgS-- and (MeHg)(2)S-exposed animals had a modest increase of the lymphocyte proliferative response. The largest concentrations of all four mercury forms were detected in the kidney and spleen. The levels of mercury found in kidney, spleen, liver, brain, and testis we re lower in the MeHgCl group than in those exposed to (MeHg)(2)S and ( MeHg)(3)S+. These data indicate that the organ distribution of mercury and immune alteration mall vary according to the chemical structure o f the compound. This observation may have important implications in hu mans potentially exposed to low levels of methylmercury pn sent in the environment, since the immune system plays an important regulatory ro le in the host-defense mechanisms.