PERCUTANEOUS TRANSPORT IN RELATION TO STRATUM-CORNEUM STRUCTURE AND LIPID-COMPOSITION

[摘要] Despite the acknowledged importance of the stratum corneum in limiting water loss and in controlling skin permeability, the basis for these functions remains unknown. To pinpoint those factor(s) of importance for cutaneous barrier function, thickness, number of cell layers and lipid composition of leg vs. abdominal stratum corneum samples with penetration of 3H-H2O and 14C-salicylic acid across the same tissue sample were correlated. Viable upper epidermal sheets were obtained by incubating fresh autopsy or amputation full-thickness skin with staphylococcal exfoliation. Each sheet was divided into 3 portions. The 1st piece was mounted in a diffusion cell for penetration studies. The 2nd stratum corneum sample was frozen sectioned, stained with the fluorochrome, ANS [8-anilino-1-naphthalene sulfonic acid] and measured with a micrometer eyepiece. The 3rd piece was pooled with other leg (n = 6) and abdomen (n = 15) specimens for determination of lipid weight percent. In all cases, leg stratum corneum was .simeq. 2-fold more permeable than abdominal stratum corneum to H2O and slightly more permeable to salicylic acid. Penetration of both substances correlated inversely with lipid weight percent of leg (mean = 3.0%) vs. abdomen (mean = 6.8%) but penetration of H2O or salicylic acid was not influenced by number of cell layers or thickness of stratum corneum. Differences in the thickness and number of cell layers in the stratum corneum were insufficient to account for differences in percutaneous transport across leg and abdomen and total lipid concentration may be the critical factor governing [human] skin permeability.