Effects of coadministered low-molecular-weight thiol compounds on short-term distribution of methyl mercury in the rat

Abstract

Following iv administration to the rat, methyl mercury was rapidly deposited in the liver, kidneys, and cerebrum. Methyl mercury concentrations in cerebrum 5 min after injection were about equal to the levels attained at 60 min post-treatment. At 5 min after dosing, concentrations of methyl mercury in plasma and tissues were directly proportional to the dose level of methyl mercury. Coadministration of equimolar amounts of l-cysteine increased short-term accumulation of methyl mercury in liver, kidneys, and cerebrum while reducing the levels of methyl mercury in plasma from those found after administration of methyl mercury alone. Equimolar doses of d-cysteine or d-penicillamine lowered plasma methyl mercury levels below those produced by injection of methyl mercury alone, but coadministered N-acetyl- l-cysteine or l-penicillamine did not. Each of these low-molecular-weight thiol compounds given in combination with methyl mercury increased deposition of methyl mercury in liver and kidneys. In addition, l-penicillamine also increased accumulation of methyl mercury in the cerebrum. These results suggest a critical role of plasma methyl mercury levels in the control of short-term methyl mercury distribution. Modification of the distribution pattern by coadministered low-molecular-weight thiol compounds further suggests that methyl mercury-thiol complexes may play a role in the tissue deposition process.