Mammary Transfer of 203Hg from Mothers to Brains of Nursing Rats

Abstract

The major routes of excretion of mercury by animals thus far studied are the kidney and gastrointestinal tract. However, lungs and mammary glands have also been known to excrete mercury (1). The mammary gland has been reported to contain radioactivity when mice were intravenously injected with 203HgC12 (2). Women (3, 4), guinea pigs2 and rats (5-7) have also been reported to secrete milk containing mercury. To our knowledge, studies to determine the quantitative transfer of mercury from lactating mothers to the nursing animals have not been reported although Trenholm et al. found from indirect evidences, insignificant concentration of mercury in guinea pigs' milk.2 Thus, our objectives were to determine quantitatively the transfer of 203Hg from mother to nursing pup and to determine the distribution of the 203Hg in various parts of maternal and pup brain.Methods. Four litters of 8 pups each of Sprague-Dawley rats at 16 days of age were allowed to suckle their own mothers. Each mother during the 16th day of lactation received a single oral dose of 30 pCi of 203Hg as CH3HgCl dissolved in 1 ml of corn oil. The specific activity of this compound was 2.25 mCi/mg Hg. When the pups were 17, 18, 19, and 21 days of age, 2 from each litter were killed. Mothers were killed at the same time as their last 2 progeny. All were killed by over-etherization and bled by an

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