EPIDERMAL AND DERMAL PHOSPHOLIPIDS OF THE HUMAN EYELID - A P-31 NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY STUDY

The phospholipids of the skin are difficult tea quantify because they represent only a small fraction of the skin tissue. In this study, P-3 1 nuclear magnetic resonance, which permits precise profiling of these phospholipids, was used to compare the phospholipids of upper eyelid epidermal and dermal lipid extracts (n = 13 profiles). Phospholipid pr ofiles included alkylacylphosphatidylcholine (AAPC), dihydrosphingomye line (DHSM), diphosphatidylglycerol (cardiolipin), ethanolamine plasma logen (EPLAS), lysophosphatidylcholine, phosphatidic acid, phosphatidy lcholine (PC), phosphatidylethanolamine, phosphatidylinositol, phospha tidylserine, sphingomyelin, and uncharacterized phospholipids (U1 and U2, particularly enriched in the epidermis). The computed phospholipid metabolic index (n = 86 indexes) findings can be summarized as follow s: a lower content of the en-ol and ether phospholipids in the epiderm is relative to the dermis, internal compensation among the component p hospholipids so as to maintain the choline functional group ratio, and a greater concentration of hydroxyl-containing functional groups in t he epidermis. A membrane index (f(mem)) value of -0.37 for the epiderm is deviated considerably from the value of -0.06 characteristic of liv ing membranes and the dermis. The production of the reduced phosphatid es, EPLAS and AAPC, indicates the use of alternative pathways between the two tissues. Relative to the dermis, increased PC in the epidermis coupled with decreased DHSM, EPLAS, and AAPC are factors enabling the epidermis of eyelid tissue to be an effective water barrier.