Nakanishi T, Uyama O, Nakahama H, Takamitsu Y, Sugita M
Fifth Department of Internal Medicine, Hyogo College of Medicine, Nishinomiya, Japan.
Am J Physiol. 1993 Mar;264(3 Pt 2):F472-9. doi: 10.1152/ajprenal.1993.264.3.F472.
Sorbitol, inositol, betaine, taurine, and glycerophosphorylcholine (GPC) are organic osmolytes that accumulate in the renal inner medulla during antidiuresis. In the cultured cell model, high medium sodium increases all the cell osmolytes and high medium urea increases cell GPC and inositol. It has been difficult, however, to discriminate between the effects of sodium and urea on organic osmolytes in water-deprived animals. To determine the nature of the in vivo responses of osmolyte accumulation induced by extracellular sodium or urea, we measured the medullary organic osmolytes and tested the degree of their linear correlation with urine and tissue parameters in control, dehydrated, salt-loaded, and urea-loaded rats. All of the osmolytes except myo-inositol increased in salt-loaded rats. Betaine and sorbitol contents in dehydrated rats were less than in salt-loaded rats, but other osmolytes increased significantly. Conversely, in urea-loaded rats, only GPC increased significantly, whereas either no change occurred for other osmolytes or sometimes betaine and sorbitol levels decreased. These data suggest that high sodium increases all of the osmolytes except myoinositol, whereas high urea increases only GPC and may decrease the renal medullary contents of betaine and sorbitol. We also demonstrated, using linear regression analysis, that urea and electrolyte in urine as well as tissue correlate well with each osmolyte measured.
山梨醇、肌醇、甜菜碱、牛磺酸和甘油磷酸胆碱（GPC）是有机渗透溶质，在抗利尿期间会在肾内髓质中蓄积。在培养细胞模型中，高培养基钠会增加所有细胞渗透溶质，高培养基尿素会增加细胞GPC和肌醇。然而，在缺水动物中，很难区分钠和尿素对有机渗透溶质的影响。为了确定细胞外钠或尿素诱导的渗透溶质蓄积的体内反应性质，我们测量了髓质有机渗透溶质，并测试了它们与对照、脱水、盐负荷和尿素负荷大鼠尿液及组织参数的线性相关程度。除肌醇外，所有渗透溶质在盐负荷大鼠中均增加。脱水大鼠中的甜菜碱和山梨醇含量低于盐负荷大鼠，但其他渗透溶质显著增加。相反，在尿素负荷大鼠中，只有GPC显著增加，而其他渗透溶质要么没有变化，要么有时甜菜碱和山梨醇水平降低。这些数据表明，高钠会增加除肌醇外的所有渗透溶质，而高尿素只会增加GPC，并且可能会降低肾髓质中甜菜碱和山梨醇的含量。我们还通过线性回归分析证明，尿液和组织中的尿素及电解质与所测量的每种渗透溶质都有很好的相关性。
