lontophoretic Permselectivity of Mammalian Skin: Characterization of Hairless Mouse and Porcine Membrane Models

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Abstract
Purpose. To evaluate the transport number of Na+, and the isoelectric point, of two skin membranes frequently used for iontophoreticin vitroresearch. Methods. Na+ transport numbers were determined by the Hittorf method or by the measurement of membrane potential. The skin isoelectric point was deduced from the electroosmosis of mannitol (a polar non-electrolyte) as a function of pH. Results. The Na+ transport number across porcine skin, like that for hairless mouse, indicated a modest cation permselectivity. Consistent with this observation, the isoelectric points of porcine and hairless mouse skin were determined to be in the ranges of 3.5−3.75 and 4.5−4.6, respectively. That is, at physiological pH, both of these model membranes supports a net negative charge. Conclusions. The permselective properties of porcine and hairless mouse skin are similar (but with the porcine membrane having apparently fewer basic or more weakly-acidic groups than that of the mouse) and consistent with the characteristics, which have been deduced elsewhere, of human skin.