Permeation in a Lipid-Soluble Form

Despite the existence of neutral metal complexes in solution that might be expected to permeate the lipid portion of cell membranes, there seem to be few systematic studies of this phenomenon in cells. In a study of the interaction of mercury with erythrocytes, Weed, Eber, and Rothstein (1962) describe the rapid uptake of Hg and in a later review Rothstein (1970) compared this to the much slower uptake of organic mercurials, P-chloro-mercuribenzoic acid (PCMB), chlormerodrin, and F-chloromercuribenzene 

Gregus et al. (1992) recently demonstrated that acute administration of high doses of dihydrolipoic acid, a lipid-soluble coenzyme containing two sulfhydryl groups, stimulates hepatic uptake and biliary excretion of mercury. The enhanced uptake presumably results from diffusion of the hydro-phobic metal complex. However, because lipoic acid is normally localized to mitochondria, it may not play a major role in metal uptake under physiological conditions. Mercury and cadmium can also form lipid-soluble complexes with selenium (Magos and Webb 1980), but the mechanisms involved have not been elucidated. 

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