Distribution of de novo synthesized betaine in rat kidney: role of renal synthesis on medullary betaine accumulation.
Distribution of de novo synthesized betaine in rat kidney: role of renal synthesis on medullary betaine accumulation.
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从头合成的甜菜碱在大鼠肾脏中的分布：肾脏合成对髓质甜菜碱积累的作用。
DOI：
10.1152/ajprenal.1997.272.1.f94
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Lien,YH
中科院分区：
文献类型：
--
作者：
Moeckel,GW;Lien,YH
三甲胺甘氨酸-甜菜碱在哺乳动物肾脏的髓质细胞中积累到高浓度，而由胆碱合成的甜菜碱主要在肾皮质中。我们研究了肾脏甜菜碱合成对髓质甜菜碱积累的贡献。通过在雄性Sprague-Dawley大鼠肾动脉内注射[14C]胆碱，原位合成甜菜碱。[14C]甜菜碱在肾皮质、肾髓质以及血清和尿液样本中测定。甜菜碱在皮层的浓度从5min时的3.5 +/- 1.3下降到60min时的0.4 +/- 0.2 nmol/mg蛋白，而在髓质的浓度从1.4 +/- 0.1上升到2.5 +/- 0.6 nmol/mg蛋白。血清和总尿[14C]甜菜碱分别从5 min时的2.7 +/- 1.3和0.9 +/- 0.1 nmol/ml增加到60 min时的5.3 +/- 0.3和2.1 +/- 0.4 nmol/ml。新合成的甜菜碱浓度未因结扎肝动脉和门静脉而降低，提示大部分[14C]甜菜碱是在肾脏合成的。共注射5 mM二甲氨基乙醇（一种胆碱氧化酶抑制剂）和100 mM冷甜菜碱分别使髓质甜菜碱积累减少了80%和76%。缺水60 h使皮质和髓质[14C]甜菜碱浓度升高，而尿尿则使髓质[14C]甜菜碱浓度降低。我们得出结论，在肾脏中合成的甜菜碱可以在髓质中积累，并且新合成的甜菜碱的髓质浓度与动物的水合状态密切相关。
The trimethylamine glycine-betaine is accumulated to high concentrations in medullary cells of mammalian kidneys, whereas betaine synthesis from choline is predominant in the renal cortex. We investigated the contribution of renal betaine synthesis to medullary betaine accumulation. De novo synthesis of betaine in situ was accomplished by injecting [14C]choline into the renal artery of male Sprague-Dawley rats. [14C]betaine was measured in the renal cortex and medulla, as well as in serum and urine samples. Betaine concentration in the cortex decreased from 3.5 +/- 1.3 at 5 min to 0.4 +/- 0.2 nmol/mg protein at 60 min, but it increased from 1.4 +/- 0.1 to 2.5 +/- 0.6 nmol/mg protein in the medulla. Serum and total urine [14C]betaine increased from 2.7 +/- 1.3 and 0.9 +/- 0.1 nmol/ml at 5 min to 5.3 +/- 0.3 and 2.1 +/- 0.4 nmol/ml at 60 min, respectively. Concentrations of newly synthesized betaine were not decreased by the ligation of the hepatic artery and portal vein, suggesting that most [14C]betaine was synthesized in the kidney. Coinjection with 5 mM dimethylamino-ethanol, a choline oxidase inhibitor, and 100 mM cold betaine reduced medullary betaine accumulation by 80 and 76%, respectively. Water deprivation for 60 h increased both cortical and medullary [14C]betaine, whereas furosemide diuresis decreased the medullary [14C]betaine concentration. We concluded that betaine synthesized in the kidney can be accumulated in the medulla and that the medullary concentrations of newly synthesized betaine are closely related to the hydration state of the animal.