Gastrointestinal absorption of inorganic mercuric compounds in vitro

Effects of intraluminal pH on the intestinal absorption and tissue binding of HgCl2 and HgO were studied in the everted sac of rat small intestine. The sac was incubated in media containing HgCl2 or HgO (10(-5 M] at different pH values. With an increase in pH, the uptake of HgCl2 in the intestinal tissue decreased and the transport of HgCl2 through the tissue increased. Similar pH dependence was observed in the uptake of HgO. The transport of HgCl2 seemed to be correlated with mercury bound to a protein (molecular weight between 440,000 and 669,000) and to be inversely correlated with that bound to intestinal metallothionein. These results suggest that the increase of intraluminal pH promotes the absorption of HgCl2 accompanied by a change in the binding of HgCl2 to the everted tissue sac.