Mechanisms of Absorption of Inorganic Mercury from Rat Small Intestine. III. Comparative Absorption Studies of Inorganic Mercuric Compounds in Vitro

Abstract

Abstract:The transport of various inorganic mercuric compounds (HgX,s) was compared in everted intestinal sacs and intestinal brush border membrane vesicles (BBMV) of the rat. The preparations were incubated in a medium containing lo-' M HgX, at pH 5.5,6.4 or 7.4, respectively. The order of transport through the intestinal wall at each pH (HgOAc), > HgCI, > Hg(SCN), > HgBr, > Hg(CN),) was the reverse order of their stability constants, and an increase in pH tended to increase the transport of HgX,. In the experiment with BBMV, similar results were obtained except for the transport of Hg(CN),. These results suggest that the extent of transport of a certain HgX, depends on its stability constant, and that the increase in pH promotes the transport possibly as a result of the conversion of HgX, to Hg(0H)X and Hg(OH12.

Intestinal Absorption of Inorganic Mercury in Rat

“…A simple process of diffusion, proportional to the concen-tration of mercury in the lumen of the intestines seems more likely. This statement conforms with data of others obtained for mercury both in vivo and in vitro, indicating that the transport of mercury across the intestinal wall is linked with water transport (Cikrt 1971;Endo et al 1988a) and depends on the chemical form and dimensions of the molecule (Cikrt 1971;Endo et al 1984Endo et al , 1988bEndo et al & 1990.…”

Localization of Gastrointestinal Deposition of Mercuric Chloride Studied in Vivo

“…The peak in mercury deposition observed in the proximal part of jejunum (around segment 7) with a maximum deposition of mercury at 3 hr and decreasing thereafter throughout the experimental period is probably internalized mercury. The localization of mercury in the proximal part of jejuneum, a few segments after the entrance of the bile duct and the ductus pancreaticus, corresponds to previous investigations demonstrating enhanced absorption of mercury at increasing pH (Endo et al 1986(Endo et al , 1988(Endo et al & 1990. The maximum value at 3 hr corresponded with the maximum blood level of mercury observed at this time.…”

Experimental localization of intestinal uptake sites for metals (Cd, Hg, Zn, Se) in vivo in mice.

“…The mercury deposition in the proximal part of jejunum with a peak at segment 7 and maximum labeling at 3 hr postdosage probably represents internalized mercury. The preferential labeling of the proximal part of jejunum, posterior to the outlets of the bile and pancreatic ducts agrees with results of previous investigations, which demonstrated enhanced absorption of mercury at increasing pH (7,13,14). Thus, the present study using the undisturbed intestinal system filled with digesta supports the studies using ligated perfused intestinal segments in vitro or in situ, indicating proximal jejunum as the major site for uptake of inorganic mercury; however, the absorption seems to occur in a larger part of jejunum than previously reported.…”