Mechanisms of absorption of inorganic mercury from rat small intestine. II. Composite effects of pH and halide ions on transport of mercuric chloride into isolated brush border membrane vesicles in rats.

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.