Moriyama T, Garcia-Perez A, Burg M B
Laboratory of Kidney and Electrolyte Metabolism, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892.
Am J Physiol. 1990 Nov;259(5 Pt 2):F847-58. doi: 10.1152/ajprenal.1990.259.5.F847.
Renal medullary cells contain high concentrations of sorbitol, inositol, glycerophosphorylcholine (GPC), and betaine, which balance the variably high osmolality of extracellular NaCl. We found that PAP-HT25 (rabbit renal medullary) cells in tissue culture increase their content of all four when medium osmolality is increased by adding NaCl and urea. However, this requires that betaine be added to medium in addition to customary constituents. Some factors affecting the mix of organic osmolytes in these cells during hypertonicity are as follows. 1) Urea in medium increases cell GPC and tends to decrease others, particularly betaine. 2) With small increases in medium NaCl, intracellular inositol is highest, whereas sorbitol predominates with large NaCl increases. 3) When osmolality is suddenly decreased, these four organic osmolytes exit rapidly from cells, but in differing relative amounts (betaine much greater than sorbitol greater than inositol much greater than GPC). 4) Altering cell betaine levels (by varying betaine in medium) causes reciprocal changes in cell sorbitol (by affecting aldose reductase activity) and vice versa, whereas inositol and GPC are less affected. 5) Raising medium glucose concentration (from which sorbitol is synthesized) increases cell sorbitol and decreases cell inositol and betaine. 6) Decreasing the amount of GPC in cells (by removing choline from medium) causes small changes in betaine and sorbitol, but not in inositol. Changing the amount of inositol does not affect the others. Similar interrelations may operate in vivo to vary the mix of organic osmolytes in renal medulla.
肾髓质细胞含有高浓度的山梨醇、肌醇、甘油磷酸胆碱（GPC）和甜菜碱，它们可平衡细胞外氯化钠变化不定的高渗透压。我们发现，在组织培养中，当通过添加氯化钠和尿素提高培养基渗透压时，PAP-HT25（兔肾髓质）细胞中这四种物质的含量都会增加。然而，这需要在培养基的常规成分之外添加甜菜碱。高渗状态下影响这些细胞中有机渗透溶质混合物的一些因素如下：1）培养基中的尿素会增加细胞内的GPC，并倾向于减少其他物质，尤其是甜菜碱。2）培养基中氯化钠少量增加时，细胞内肌醇含量最高，而氯化钠大量增加时，山梨醇占主导。3）当渗透压突然降低时，这四种有机渗透溶质会迅速从细胞中排出，但相对量不同（甜菜碱远大于山梨醇大于肌醇远大于GPC）。4）改变细胞甜菜碱水平（通过改变培养基中的甜菜碱含量）会导致细胞中山梨醇发生相反变化（通过影响醛糖还原酶活性），反之亦然，而肌醇和GPC受影响较小。5）提高培养基葡萄糖浓度（山梨醇由此合成）会增加细胞中山梨醇含量，并降低细胞内肌醇和甜菜碱含量。6）减少细胞内GPC含量（通过从培养基中去除胆碱）会使甜菜碱和山梨醇发生小的变化，但对肌醇无影响。改变肌醇含量不会影响其他物质。类似的相互关系可能在体内发挥作用，以改变肾髓质中有机渗透溶质的混合物。
