Bjørnstad P, Bremer J
J Lipid Res. 1966 Jan;7(1):38-45.
The in vivo biosynthesis of lecithin in rats has been studied with the precursors choline-1,2-(14)C, ethanolamine-1,2-(14)C and methionine-CH(3)-(14)C or -CH(3)-(3)H. Lecithin synthesis from choline is rapid in all organs. No sex difference was observed in this pathway. The biosynthesis of lecithin by methylation of phosphatidyl ethanolamine is of quantitative significance in the liver, but not in extrahepatic tissues. More lecithin is synthesized by this pathway in female rats. In liver the lecithin synthesized via both pathways enters a common pool which is in rapid equilibrium with lecithin of blood plasma. A sex difference in the utilization of radioactive ethanolamine for the formation of phosphatidyl ethanolamine was observed (greater utilization in the female). Incorporation of ethanolamine into phospholipids of extrahepatic tissues was slow in both sexes. With labeled methionine as precursor the liver cytidine diphosphate (CDP) choline had a specific activity identical with that of liver lecithin after 20 min, while the specific activity of phosphoryl choline remained low. With labeled choline as precursor the phosphoryl choline reached a specific activity 50 times that of lecithin after 20 min, while the specific activity of CDP choline was only four times that of lecithin. These findings indicate that the reaction: CDP choline + diglyceride right harpoon over left harpoon phosphatidyl choline + CMP is freely reversible in vivo.
利用前体胆碱-1,2-(14)C、乙醇胺-1,2-(14)C和蛋氨酸-CH(3)-(14)C或-CH(3)-(3)H对大鼠体内卵磷脂的生物合成进行了研究。胆碱合成卵磷脂在所有器官中都很快。在这条途径中未观察到性别差异。通过磷脂酰乙醇胺甲基化合成卵磷脂在肝脏中具有定量意义，但在肝外组织中并非如此。雌性大鼠通过这条途径合成的卵磷脂更多。在肝脏中，通过这两条途径合成的卵磷脂进入一个共同的池，该池与血浆卵磷脂处于快速平衡状态。观察到在利用放射性乙醇胺形成磷脂酰乙醇胺方面存在性别差异（雌性利用率更高）。两性中乙醇胺掺入肝外组织磷脂的速度都很慢。以前体标记蛋氨酸为例，20分钟后肝脏胞苷二磷酸（CDP）胆碱的比活性与肝脏卵磷脂的比活性相同，而磷酸胆碱的比活性仍然很低。以前体标记胆碱为例，20分钟后磷酸胆碱的比活性达到卵磷脂的50倍，而CDP胆碱的比活性仅为卵磷脂的四倍。这些发现表明反应：CDP胆碱+甘油二酯⇌磷脂酰胆碱+CMP在体内是自由可逆的。
