LACTATIONAL EXPOSURE TO METHYLMERCURY IN THE HAMSTER

Syrian Golden hamster dams were administered Hg-203-labelled methyl mercury (MeHg; 1.6 mu mol/kg) 1 day after parturition and milk was collected twice during the Ist week. The excretion of Hg-203 in milk and the uptake, retention and tissue distribution of Hg-203 in, the pups was studied using gamma counting. The fraction of inorganic Hg in milk and in the kidneys of the pups was determined following separation of inorganic Hg and MeHg by ion exchange chromatography. The concentration of Hg-203 in milk on the Ist day after MeHg administration was 0.12 nmol/g. Hg-203 was mainly (80-90%) excreted as MeHg during the first 6 days of lactation. The whole body and tissue concentration of Hg-203 in the pups increased for 10-15 days and decreased thereafter. The content of Hg-203 in the pelt and the fraction of inorganic Hg in the kidney increased throughout the study period (4 weeks). The excretion of MeHg in milk corresponded to at least 5% of the dose administered to the dam. Our study demonstrates that breast milk may be a significant source of MeHg exposure during the critical neonatal period.