SELENIUM CONCENTRATIONS IN BRAIN AFTER EXPOSURE TO METHYLMERCURY - RELATIONS BETWEEN THE INORGANIC MERCURY FRACTION AND SELENIUM

Three groups of female monkeys (Macaca fascicularis) were exposed to m ethylmercury (MeHg, p.o. 50 mu g HE/kg body wt per day) for 6, 12, or 18 months, One group was exposed to MeHg for 12 months and kept unexpo sed for 6 months before sacrifice. Another group of three monkeys was exposed to HgCl2 i.v. for 3 months. Total and inorganic mercury concen trations in occipital pole and thalamus were determined by cold vapor atomic absorption spectroscopy. Selenium concentrations were analyzed by hydride generation atomic absorption spectroscopy, The results indi cated an association between concentrations of inorganic mercury and s elenium in both occipital pole and thalamus in the MeHg-exposed animal s, A linear regression model using concentrations of inorganic mercury (nmol/g wet wt) as independent variable, and selenium concentrations (nmol/g wet wt) as the dependent variable showed significant correlati ons between the variables in both occipital pole and thalamus (r = 0.8 5 and r = 0.91, P < 0.0001). The intercept of the regression line was slightly lower (about 2 nmol Se/g wet wt) than the selenium concentrat ions found in control monkeys (about 3 nmol Se/g wet wt). There was a tendency to a ''hockey stick''-shaped relationship between concentrati ons of selenium and inorganic mercury in the thalamus of monkeys with ongoing exposure to MeHg. An important role for selenium in the retent ion of mercury in brain is indicated.