Factors involved in absorption of organic mercuric compounds from rat small intestine: comparative study with mercuric chloride in situ.

A correlation between absorption of organic mercuric compounds and their molecular weight or lipophilicity was investigated by the perfusion of rat small intestine. The intestine was perfused for 1.0 hr at different osmolarity and different pH with buffers containing 10(-4) M organic mercuric compounds, methyl mercuric chloride (MMC), phenyl mercuric chloride (PMC), p-chloromercuribenzoic acid (PCMB) and p-chloromercuriphenylsulfonic acid (PCMBS). The order of absorption of these compounds at several osmolarities and pHs (MMC greater than PMC greater than PCMB greater than PCMBS) was inversely correlated to their molecular weight. The increase in pH decreased markedly the absorption and n-octanol/water partition coefficient of PCMB, and it decreased scarcely those of MMC, PMC and PCMBS. The order of the coefficients at each pH was as follows; PMC greater than MMC greater than PCMB greater than PCMBS, in disagreement with the order of absorption. These results suggest that the molecular weight is more important factor in the intestinal absorption of organic mercuric compounds than the lipophilicity.