Milk transfer of inorganic mercury to suckling rats. Interaction with selenite.

The transport of mercury into rat milk, and uptake in the suckling offspring was studied after peroral administration of inorganic mercury to lactating control rats, and to rats fed selenite in the diet. On day 8, 9, 10, or 11 of lactation, dams were administered a single oral dose of 0.1, 0.4, 0.7, 1.3, or 5.8 mg Hg/kg bw labeled with 203mercuric acetate. There was a linear relationship between mercury concentrations in dam's plasma and milk. The level of mercury in milk was approximately 25% of the level in plasma. After 3 d, milk levels were reduced to half the levels at 24 h. In the suckling offspring, exposed to mercury via milk during 3 d, the mercury level in blood was approximately 1% of the level in maternal blood. Mercury concentration in milk was linearly correlated to the levels in kidney, liver, and brain in the suckling offspring after 3 d exposure to mercury via milk. Selenite treatment of rats, 1.3 micrograms Se/g diet for 5 mo, resulted in increased transport of mercury to milk, probably because of increased plasma levels of mercury. However, selenite treatment of the dams did not cause any increased tissue levels of mercury in the suckling offspring.