The mechanism of water binding in stratum corneum.

Abstract

SUMMARY.— The results presented in this paper confirm the published observations by others that the hygroscopic water-soluble substances within the corneum are responsible for much of the water binding ability of the horny layer. The ability of corneum to bind water is reduced when it is extracted with solvents, which remove lipid, and then with water, which removes the water-soluble substances. Our interpretation of this is that the water-soluble substances are retained within the corneum by a lipid-containing semipermeable membrane system which allows these substances to take up water by osmosis and protects them from dissolution when the intact corneum is immersed in water. Our experiments show that isolated corneum from guinea-pig footpads and from human palms, soles and abdomen can take up and lose water by osmosis. Powdering the corneum allows water to extract the water-soluble substances without a prior solvent extraction. The powdering procedure ruptures the cell walls of the corneum cells and we propose that it is the cell walls which make up the lipid containing semi permeable membrane system. A method for measuring extensibility of isolated strips of corneum in a humid atmosphere has been developed. Using this technique it has been shown that it is the water held by the water-soluble substances that is responsible for most of the extensibility of corneum.