THE METABOLISM OF L-ARGININE AND ITS SIGNIFICANCE FOR THE BIOSYNTHESIS OF ENDOTHELIUM-DERIVED RELAXING FACTOR - CULTURED ENDOTHELIAL-CELLS RECYCLE L-CITRULLINE TO L-ARGININE
THE METABOLISM OF L-ARGININE AND ITS SIGNIFICANCE FOR THE BIOSYNTHESIS OF ENDOTHELIUM-DERIVED RELAXING FACTOR - CULTURED ENDOTHELIAL-CELLS RECYCLE L-CITRULLINE TO L-ARGININE
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DOI：
10.1073/pnas.87.21.8612
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发表时间：
1990-11-01
影响因子：
11.1
通讯作者：
VANE, JR
中科院分区：
文献类型：
--
作者：
HECKER, M;SESSA, WC;VANE, JR
我们研究了培养的内皮细胞产生L-精氨酸（L-Arg）的机制，L-精氨酸是内皮源性舒张因子生物合成的底物。当Arg耗尽的内皮细胞在Kreb's溶液中孵育60分钟时，L-Arg水平显著升高（9.7倍）。L-Arg的产生与细胞内L-谷氨酰胺（L-Gln）的大幅减少（90%）相一致，而所有其他氨基酸几乎不受影响。钙，pH值，或氧张力的变化对L-Arg的产生没有影响，然而，当细胞在含有L-Gln的培养基中孵育时，可以防止L-Arg的产生。用L-[14 C]Arg标记的内皮细胞产生的L-Arg来自未标记的细胞内来源，因为细胞内L-Arg库的比活性在60分钟内大幅下降（8.8倍）。Arg耗尽的内皮细胞不形成尿素或代谢L-鸟氨酸，但可能通过形成L-精氨酸琥珀酸将L-瓜氨酸（L-Cit）转化为L-Arg。用钙离子载体A23187刺激的非耗竭细胞仅显示L-Cit的瞬时积累，表明L-Cit在内皮衍生的松弛因子的生物合成期间再循环为L-Arg。精氨酸耗尽的内皮细胞的L-Arg的产生被蛋白酶抑制剂部分阻断（45%），并且各种含精氨酸的二肽被快速切割以产生L-Arg。因此，培养的内皮细胞将L-Cit再循环为L-Arg并可能释放肽基L-Arg。Arg-Cit循环在内皮细胞中似乎等同于肝脏形成尿素。因此，内皮源性舒张因子的生物合成不仅可以产生强大的血管扩张剂，而且可以减轻内皮细胞的过量氮。
We have investigated the mechanism by which cultured endothelial cells generate L-arginine (L-Arg), the substrate for the biosynthesis of endothelium-derived relaxing factor. When Arg-depleted endothelial cells were incubated in Kreb''s solution for 60 min, L-Arg levels were significantly (9.7-fold) elevated. The generation of L-Arg coincided with a substantial decrease (90%) in intracellular L-glutamine (L-Gln), whereas all other amino acids were virtually unaffected. Changes in calcium, pH, or oxygen tension had no effect on L-Arg generation, which was, however, prevented when the cells were incubated in culture medium containing L-Gln. L-Arg generated by endothelial cells labeled with L-[14C]Arg was derived from an unlabeled intracellular source, for the specific activity of the intracellular L-Arg pool decreased substantially (8.8-fold) over 60 min. Arg-depleted endothelial cells did not form urea or metabolize L-ornithine but converted L-citrulline (L-Cit) to L-Arg possibly via formation of L-argininosuccinic acid. Nondepleted cells stimulated with the calcium ionophore A23187 showed only a transient accumulation of L-Cit indicating that L-Cit is recycled to L-Arg during the biosynthesis of endothelium-derived relaxing factor. The generation of L-Arg by Arg-depleted endothelial cells was partially (45%) blocked by protease inhibitors, and various Arg-containing dipeptides were rapidly cleaved to yield L-Arg. Thus, cultured endothelial cells recycle L-Cit to L-Arg and possibly liberate peptidyl L-Arg. The Arg-Cit cycle appears to be the equivalent in the endothelial cell to the formation of urea by the liver. The biosynthesis of endothelium-derived relaxing factor may, therefore, not only produce a powerful vasodilator but also relieve the endothelial cell of excess nitrogen.