Objectives: Stratum corneum (SC) from both hard palate and epidermis contain ceramides, cholesterol and fatty acids as major lipid components. These lipids determine the barrier function of the tissue. The least polar of the ceramides in both regions is a structurally unusual acylceramide consisting of 30- through 34-carbon
w-hydroxyacids amide-linked to sphingosine bases and bearing ester-linked fatty acid on the
w-hydroxyl group. The present hypothesis was that compositions of ester linked fatty acids will be the same for both epidermal and palatal acylceramides. Methods: Epidermis and palatal epithelium were both obtained from one pig. Lipids were extracted into chloroform:methanol mixtures, and the acylceramides were isolated in parallel by preparative thin-layer chromatography. The isolated acylceramides were treated with 10% boron trichloride in methanol at 50
o C for 60 min. The normal fatty acid methyl esters were isolated by preparative thin-layer chromatography and analyzed by gas-liquid chromatography using a 30 m EC-Wax capillary column and a flame ionization detector. Results: In epidermal SC the most abundant fatty acids were linoleic acid (C18:2, 67.0 %) and arachidic acid (C20:0, 13.4%). In contrast, the palatal acylceramide contained stearic acid (C18:0, 39.8%), palmitic acid (C16:0, 29.2%) and oleic acid (C18:1, 13.3%) as the most abundant species. Linoleate was only 8.0% of the ester-linked fatty acid in palatal acylceramide. Conclusion: It is concluded that acylceramides from epidermis and palatal SC contain different ester-linked fatty acid profiles. Acylceramide has been suggested to play a central role in the organization and barrier function of the lipids in epidermal SC, and the high proportion of linoleate in this lipid is essential for maintaining barrier function. The diminished proportion of linoleate in palatal acylceramide may, at least in part, explain the diminished barrier function of palate compared to the skin. Supported in part by NIH grant DEO0175.