Generation of novel metabolites of dietary linoleic acid (18:2n6) by guinea pig epidermis

Although the authors have demonstrated the inability of rat and guinea pig (GP) skin enzyme preparations to desaturate 18:2n6 into gammalinolenic acid (18:3n6) using an in vitro microsomal system, the fate of this dietary essential fatty acid in the GP epidermis is unknown. To explore the fate of 18:2n6, intact tissue slices from GP epidermis were incubated with [1-14C]18:2n6. After incubation, the extracted lipids were transesterified using methanolic-HCL. The fatty acid methyl esters were analyzed using a combination of (i) argentation TLC, scanned using a proportional TLC radioscanner, and (ii) reverse phase HPLC, equipped with a flow through radioscanner. The results indicate that the intact epidermis metabolized 14C-18:2n6 to a group of novel products more polar than 18:2n6. In subsequent experiments, 14C-18:2n6 was either incubated with the 800 xg supernatant, the 105,000 xg pellet or supernatant from GP epidermis. Metabolism of 18:2n6 by the high speed supernatant resulted in the generation of polar products with chromatographic properties of not greater than 2 double bonds. These results indicate that although the GP epidermis lacks the capacity to desaturate 18:2n6 to 18:3n6, it can convert dietary 18:2n6 into a group of novel polar metabolites via a cytosolic mediated process. The function of these metabolites in the GP integumentary system remains to be determined