Effect of essential fatty acid deficiency on the epidermal sphingolipids of the rat.

The epidermal sphingolipids from rats maintained on either a rat stock diet or a fat-free diet have been analyzed. Thin-layer chromatographic analyses have revealed glucosylceramides, acylglucosylceramides and four fractions of ceramides, one of which proved to be an acylceramide. The relative amounts of the glucosylceramides, acylglucosylceramides and acylceramides were increased in the essential fatty acid-deficient epidermis while one ceramide fraction was diminished. The other two ceramide fractions remained unchanged. The acylceramides and acylglucosylceramides from normal rat epidermis both contained long-chain omega-hydroxy acids in amide linkage to sphingosine bases and high proportions of linoleic acid in ester linkage. The linoleate, which is known to be crucial for the formation and maintenance of the epidermal water barrier, was replaced by oleate in the essential fatty acid-deficient rats.