Metabolism of linoleic acid in porcine epidermis.

The time course of linoleic acid metabolism in porcine epidermis has been studied in order to better evaluate the lipid transformations that accompany differentiation in this tissue. One day after intradermal injection of [U-14C]linoleic acid, most of the radioactivity in the epidermis was associated with phospholipids, triglycerides, and free fatty acids. Within 3-7 days, a portion of the radiolabel was selectively transferred to acylglucosylceramide and acylceramide fractions, after which the specific activities of all lipids fractions decreased. The results suggest that neither the lipoxygenation of linoleate nor the hydrolysis of acylceramide to form acylacid and free sphingosine are major routes of linoleate metabolism in normal epidermis. The principal pathway of linoleate metabolism in normal epidermis appears to be transfer from phospholipids to acylglucosylceramide to acylceramide. The triglyceride fraction, although minor in amount, attains an initially high specific activity, and may serve as an intermediate in linoleate transfer.