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A correlation of mercury absorption with water absorption was investigated by using the perfusion of rat small intestine with buffers containing 10(-4) M HgCl2. With a decrease in the osmolarity of the buffers or with increases in the sodium ion and urea concentrations in the buffers, absorption of water and mercury and accumulation of mercury in the intestinal tissue increased, and the increases in mercury absorption and accumulation were found to correlate with the increase in water absorption. Both the decrease in osmolarity and the increase in sodium ion concentration increased mercury accumulation in the epithelial cell after the perfusion. But these changes did not alter the mercury distribution in subcellular fractions. The results suggest that the increase in water absorption due to the hyptonicity or the increase in concentration of sodium ion or urea increases the mercury absorption and accumulation in the epithelial cell without change in the distributional pattern of mercury in the cell.

Composite effects of pH and halide ions on the transport of HgCl2 into brush border membrane vesicles (BBMV) were investigated in rats. BBMV were incubated for 10 min. in buffer solution at different pH containing 10(-4) M HgCl2. The increase in pH increased the uptake of Hg by BBMV as a result of the increase in transport of Hg into intravesicular space and decrease in binding of Hg to BBMV. The isotonic displacement of NaCl in the buffer solution by LiCl or KCl did not change the uptake of Hg at each pH. The displacement of NaCl by mannitol increased the uptake of Hg at each pH, while the displacement by NaBr or NaI decreased the uptake and diminished the increasing effect of pH on the uptake of Hg. These changes in uptake of Hg due to the displacement were mainly ascribed to the changes in transport of Hg. These results suggest that the increase in pH mainly increases the transport of HgCl2 as a result of the conversion to hydroxide forms of Hg such as Hg(OH)Cl and Hg(OH)2, and Cl- Br- and I- act as the competing ions with OH- and decrease the transport of Hg.

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.