Mechanisms of absorption of inorganic mercury from rat small intestine. IV: Effect of chelating agents and cysteine on absorption of mercuric chloride in situ and in vitro.

The effects of chelating agents (citric acid, tartaric acid, penicillamine and ethylenediaminetetraacetic acid) and cysteine on the absorption of HgCl2 were investigated in rats. Perfusion of the small intestine showed that the chelating agents and cysteine decreased the absorption of HgCl2 depending on their stability of constants with Hg2+, under the predominant conditions of water absorption and secretion. The difference in absorption of HgCl2 between both conditions was inversely correlated with their logarithmic stability constant values. These agents decreased the transport of HgCl2 through the everted intestinal wall and the uptake of HgCl2 by the intestinal brush border membrane in a similar manner. From these results, it is suggested that the chelating agents and cysteine decrease the absorption of HgCl2 through the pores of the brush border membrane due to the solvent drag effect.