PENETRATION OF LUCIFER YELLOW INTO HUMAN SKIN - A LATERAL DIFFUSION CHANNEL IN THE STRATUM-CORNEUM

We investigated the penetration of Lucifer Yellow into human and murin e epidermis in 4-mm punch biopsies by incubation in dye solution. Luci fer Yellow was taken up freely by the dermis but penetrated only sligh tly into keratinocytes of the basal and suprabasal layers. However, pr ogressive lateral diffusion was observed in the lowest layers of the s tratum corneum, extending a distance of 1 mm in 6 hr. Under high magni fication, Lucifer Yellow appeared to lie within rather than between co rneocytes of this layer. Control samples stained with Lucifer Yellow a fter sectioning showed no preferential binding of the dye in this regi on. We concluded that the localization of staining was the result of d iffusion from the cut edge of the stratum corneum. Lucifer Yellow pene tration was insensitive to PMSF, 1:10 phenanthroline, or N-ethyl malei mide and was also observed in an in vivo injury, indicating that it wa s not an artifact of proteolytic or degenerative changes. In contrast, horseradish peroxidase failed to penetrate, suggesting molecular size limitation to channel entry. Diffusion of Lucifer Yellow beneath the stratum corneum marks a pathway for the lateral movement of small mole cules of potential importance in the normal physiology of the skin, dr ug delivery, and pathology.