Hedberg C L, Wertz P W, Downing D T
Department of Dermatology, University of Iowa College of Medicine, Iowa City 52242.
J Invest Dermatol. 1988 Feb;90(2):225-9. doi: 10.1111/1523-1747.ep12462257.
Epidermis was removed from several sites on the intact bodies of each of seven pigs and the lipids were extracted and analyzed by thin-layer chromatography. The principal nonpolar components were cholesterol, free fatty acids and cholesteryl esters. Small and variable amounts of paraffin hydrocarbons, triglycerides, and an unidentified lipid were noted. In a series of time-course experiments, epidermal lipids were labeled by intradermal injection of [1-14C] acetate at varying times up to 21 days before removal of the epidermis. The hydrocarbons never acquired radioactivity, while the triglycerides retained label only for about 1 day after injection. Squalene and lanosterol retained considerable radioactivity for up to 12 h after labeling. Radioactivity appeared in free fatty acids and cholesteryl esters 2-3 days after labeling and began to decline after 21 days. Epidermis from uninjected sites did not acquire significant radioactivity. From these results it was concluded that cholesterol, cholesteryl esters and free fatty acids are synthesized locally in the epidermis and remain until lost by desquamation. Triglycerides are also synthesized but do not persist into the stratum corneum, so the small amounts found there may be environmental contaminants. Alkanes are not synthesized, and are most probably derived from petroleum waxes.
从七头猪每头的完整身体上的几个部位去除表皮，提取脂质并通过薄层色谱法进行分析。主要的非极性成分是胆固醇、游离脂肪酸和胆固醇酯。发现有少量且数量不定的链烷烃、甘油三酯和一种未鉴定的脂质。在一系列时间进程实验中，在去除表皮前长达21天的不同时间通过皮内注射[1-14C]乙酸盐对表皮脂质进行标记。链烷烃从未获得放射性，而甘油三酯在注射后仅保留约1天的标记。角鲨烯和羊毛甾醇在标记后长达12小时内保留相当多的放射性。放射性在标记后2 - 3天出现在游离脂肪酸和胆固醇酯中，并在21天后开始下降。未注射部位的表皮未获得明显的放射性。从这些结果可以得出结论，胆固醇、胆固醇酯和游离脂肪酸在表皮中局部合成，并一直保留到通过脱屑而丢失。甘油三酯也被合成，但不会持续进入角质层，所以在那里发现的少量甘油三酯可能是环境污染物。烷烃不是合成的，很可能来自石油蜡。
