Bicarbonate dependency of betaine synthesis in cultured LLC-PK1 cells.
Bicarbonate dependency of betaine synthesis in cultured LLC-PK1 cells.
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培养的 LLC-PK1 细胞中甜菜碱合成的碳酸氢盐依赖性。
DOI：
10.1152/ajprenal.1994.266.3.f512
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发表时间：
1994
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
甜菜碱是肾脏的主要有机渗透剂之一，由胆碱在肾脏中通过胆碱脱氢酶(EC 1.1.99.1)和甜菜碱醛脱氢酶(EC 1.2.1.8)合成。最近的一项体外研究表明，肾皮质匀浆合成甜菜碱依赖于毫摩尔量的碳酸氢盐。本研究旨在探讨培养的LLC-PK1细胞中甜菜碱形成对碳酸氢盐的依赖性。数据显示，甜菜碱的形成随着胞外碳酸氢盐水平的上升而增加。测得的[14C]甜菜碱合成量从13.4+/-1.5(4.6 mM HCO3-)到38.0+/-1.4微克蛋白质-1.h-1(24 mM HCO3-)。碳酸酐酶抑制剂乙酰唑胺被添加到培养基中以阻止重碳酸盐的运输，使胆碱合成甜菜碱的量减少了41%-49%。我们得出结论，LLC-PK1细胞中甜菜碱的合成依赖于胞外碳酸氢盐水平，并且通过抑制碳酸氢酶而减少。由于甜菜碱在抗利尿过程中积聚在肾髓质中，我们的观察表明酸碱平衡和肾脏中的浓度机制之间可能存在联系。
Betaine, one of the major renal organic osmolytes, is synthesized from choline by choline dehydrogenase (EC 1.1.99.1) and betaine-aldehyde dehydrogenase (EC 1.2.1.8) in the kidney. A recent in vitro study has shown that betaine synthesis by renal cortical homogenate is dependent on millimolar amounts of bicarbonate. The present study was aimed to investigate the bicarbonate dependency of betaine formation in cultured LLC-PK1 cells. The data show that betaine formation increases in accordance with a rise in extracellular bicarbonate levels. The measured quantities of [14C]betaine synthesis ranged from 13.4 +/- 1.5 (4.6 mM HCO3-) to 38.0 +/- 1.4 pmol.micrograms protein-1.h-1 (24 mM HCO3-). The carbonic anhydrase inhibitor acetazolamide, added to the incubation medium to block bicarbonate transport, reduced betaine synthesis from choline by 41-49%. We conclude that betaine synthesis in LLC-PK1 cells is dependent on extracellular bicarbonate levels and is reduced by the inhibition of carbonic anhydrase. Because betaine accumulates in renal medulla during antidiuresis, our observations suggest a possible link between acid-base homeostasis and concentration mechanisms in the kidney.