EVIDENCE FOR A NOVEL KERATINOCYTE FATTY-ACID UPTAKE MECHANISM WITH PREFERENCE FOR LINOLEIC-ACID - COMPARISON OF OLEIC AND LINOLEIC-ACID UPTAKE BY CULTURED HUMAN KERATINOCYTES, FIBROBLASTS AND A HUMAN HEPATOMA-CELL

Keratinocytes require the essential fatty acid (FA), linoleic acid (LA ), for the synthesis of stratum corneum membrane lipids. A plasma memb rane-FA binding protein (PM-FABP), is postulated to mediate cellular F A-uptake in hepatocytes and several other tissues, but the mechanism w hereby exogenous FA are taken up by keratinocytes has not been investi gated. This study examines the uptake of LA and oleic acid (non-essent ial) in cultured human keratinocytes, in comparison to dermal fibrobla sts and the human hepatoma cell line, HepG2. As previously reported fo r hepatocytes, FA-uptake in keratinocytes was curvilinear, with an ini tial (30 s) rapid cellular influx. The initial uptake component was te mperature dependent, exhibited saturable kinetics and was significantl y inhibited by pretreatment with trypsin. In contrast, fibroblast FA-u ptake lacked an initial rapid uptake component, was relatively tempera ture insensitive, and was not inhibited by trypsin. Keratinocytes diff ered from both hepatocytes and fibroblasts by more rapid uptake of LA in comparison to oleic acid during the initial influx phase. Moreover, FA-uptake in keratinocytes was not inhibited by preincubation with a anti-rat liver PM-FABP antibody. These data provide evidence for a PM- FA transporter in keratinocytes that is distinct from the hepatic PM-F ABP. The apparent preference of the putative keratinocyte FA transport er for LA may function to ensure epidermal capture of sufficient LA fo r barrier lipid synthesis.