Chapkin R S, Ziboh V A
Biochem Biophys Res Commun. 1984 Nov 14;124(3):784-92. doi: 10.1016/0006-291x(84)91026-x.
The lack of any information as to the origin of epidermal arachidonic acid, an important precursor of eicosanoids in the epidermis, prompted us to determine in vitro whether or not microsomal preparations from rat and guinea pig epidermis possess the delta 6 and delta 5 desaturase activities. The incubations were performed in parallel with microsomal preparations from liver of these animals where activities for these enzymes have previously been reported. The conversions of radioactive fatty acids were determined after methylation and separation of the 14C-fatty acid methyl esters by argentation thin layer chromatography. Data from these studies demonstrated that delta 5 desaturase activity is markedly lower in guinea pig liver than in rat liver. Interestingly, preparations from rat and guinea pig epidermis at all concentrations tested lacked the capacity to transform either linoleic acid into gammalinolenic acid or dihomogammalinolenic acid into arachidonic acid. This observation implies that arachidonic acid that is present in the epidermal phospholipids is biosynthesized elsewhere endogenously and transported to the epidermis for esterification into the phospholipids. The site of this biosynthesis is presumably the liver and the mode of transport to the epidermis remains to be determined. These studies indicate arachidonic acid per se as an essential fatty acid for the epidermis.
表皮花生四烯酸是表皮中类花生酸的重要前体，但目前尚无关于其来源的任何信息，这促使我们在体外测定大鼠和豚鼠表皮的微粒体制剂是否具有δ6和δ5去饱和酶活性。这些孵育实验与这些动物肝脏的微粒体制剂同时进行，之前已有报道这些酶在肝脏中的活性。放射性脂肪酸经甲基化后，通过银化薄层色谱法分离14C-脂肪酸甲酯，然后测定其转化率。这些研究数据表明，豚鼠肝脏中的δ5去饱和酶活性明显低于大鼠肝脏。有趣的是，在所有测试浓度下，大鼠和豚鼠表皮的制剂都缺乏将亚油酸转化为γ-亚麻酸或将二高γ-亚麻酸转化为花生四烯酸的能力。这一观察结果表明，表皮磷脂中存在的花生四烯酸是在其他地方内源性生物合成的，然后运输到表皮并酯化到磷脂中。这种生物合成的部位可能是肝脏，而运输到表皮的方式仍有待确定。这些研究表明花生四烯酸本身是表皮的一种必需脂肪酸。
