Electron probe analysis of human skin: element concentration profiles

Abstract

Concentration profiles for the major biological inorganic elements Na, P, S, Cl, and K were measured across human skin using electron probe analysis and analytical electron microscopy. Determinations were made within the cytoplasm of individual cells. Uniform element concentrations were present throughout the viable tissue, whereas element profiles in the stratum corneum were considerably diverse. Phosphorus was practically absent from the stratum corneum. Sulfur (per unit volume) continuously increased from the inner to the outer cell layers of the stratum corneum largely as a result of cytoplasmic water loss as cells migrate to the surface. Potassium was essentially excluded from the inner stratum corneum. Very large gradients for K, Na, and Cl occurred from the middle of the stratum corneum to its outer surface; these gradients are likely the result of the inward diffusion of salts from sweat and could play a variety of physiological roles. The paucity of K and P within the inner stratum corneum suggests these important intracellular solutes (and perhaps others, including water) are recycled within the viable tissue, thus providing a virtual nutrient supply immediately underneath the stratum corneum. Alterations in this recirculation could have a regulatory function in the physiology of this tissue.