Thin-layer chromatographic analyses of lipids in different layers of porcine epidermis and oral epithelium

Abstract

Frozen cryosections were cut parallel to the surface of porcine skin and palatal, buccal and floor-of-mouth mucosa so as to provide separate samples representing various epithelial layers. The samples were dried, extracted with chloroform:methanol, and the lipids were chromatographed on silica gel plates in various solvent systems. After charring, lipids were quantified with a scanning densitometer. Overall, greater differences in proportions and distributions of lipid components were evident between keratinized and non-keratinized epithelia than between epidermis and keratinized oral epithelium. For epidermis and palate there was an increase in neutral lipids, including ceramides, from the deeper layers to the surface; ceramides were most abundant in surface layers. In buccal epithelium there was a distinct increase in glycosylceramides toward the surface, and in both non-keratinized regions ceramides were present in only very small amounts. The results suggest that although neutral lipids may be associated with a superficial barrier layer in skin and oral mucosa, there are differences in the composition of this barrier between keratinized and non-keratinized epithelia.