Human skin is permselective for the small, monovalent cations sodium and potassium but not for nickel and chromium.
La Count-TD; Kasting-GB
J Pharm Sci 2013 Jul; 102(7):2241-2253
The molar conductance of excised human skin (lambda(skin)) immersed in electrolyte solutions comprising four cationic (Na(+), K(+), Ni(2+), and Cr(3+)) and five anionic (Cl(-), NO3(-), SO4(2-), CrO4(2-), and Cr2O7(2-)) species was determined as a function of concentration in Franz diffusion cells. Cation transport numbers for four of these electrolytes were measured in Franz cells by the electromotive force method. Parallel experiments were conducted in solutions alone to establish the validity of the technique. Molar conductance decreased with increasing concentration, following the Kohlrausch law, over a 4-12-fold concentration range. Molar conductance and cation transport values at infinite dilution were extrapolated from these data and used to estimate ionic conductances at infinite dilution. These values were subsequently used to calculate limiting ion mobilities and diffusivities in solution and skin. Results for skin showed the expected increase in cation permselectivity for monovalent cations and a 40-110-fold reduction in effective diffusivities with respect to those in solution. However, Ni(2+) and Cr(3+) were relatively less mobile in skin than in solution. Salt diffusivities calculated from ionic mobilities in skin provided a partial explanation for the difference in allergenic potency of NiCl2 compared with NiSO4 and Cr(3+) versus Cr(6+) salts.
Humans; Skin; Chromium-compounds; Nickel-compounds; Sodium-compounds; Potassium-compounds; Ion-transport; Metabolism; Metabolic-activation; Skin-absorption; Models; Electrolytes; Cell-metabolism; Diffusion-analysis; Mathematical-models; Membrane-filters;
Author Keywords: skin; permeability; mobility; membrane conductance/resistance; iontophoresis;
membrane transport; polar pathway; mathematical model; nickel; chromium
Gerald B. Kasting, Winkle College of Pharmacy, University of Cincinnati Academic Health Center, Cincinnati, OH 45267
7440-47-3; 7440-02-0; 7440-23-5; 7440-09-7
Journal of Pharmaceutical Sciences
University of Cincinnati