Nakanishi T, Nishihara F, Yamauchi A, Yamamoto S, Sugita M, Takamitsu Y
Department of Kidney and Dialysis, Hyogo College of Medicine, Nishinomiya, Japan.
Am J Physiol. 1996 Dec;271(6 Pt 2):F1255-63. doi: 10.1152/ajprenal.1996.271.6.F1255.
As we recently demonstrated that in potassium depletion a decrease in inner medullary organic osmolytes might precede and cause a renal concentrating defect, we hypothesized that in the protein deprivation the same mechanism may occur. To clarify the relationship between renal medullary organic osmolytes and urine concentration defects during protein deprivation, we examined the effect of protein malnutrition on organic osmolyte content after water deprivation or sodium and/or urea infusion. Water deprivation did not restore urine urea and osmolality or tissue sodium and urea in protein-deprived rats to control levels. NaCl infusion only increased urinary and medullary Na. Urea infusion increased medullary urea but not urine urea. NaCl plus urea infusion increased only urinary sodium and urea. Regardless of the protocols of hyperosmolality used, protein deprivation significantly decreased the medullary contents of myo-inositol and taurine and the level of sodium-dependent myo-inositol transporter mRNA. We conclude that factors other than NaCl and urea but associated with protein feeding are responsible for the decreased accumulation of organic osmolytes.
由于我们最近证明，在钾缺乏时，髓质内有机渗透溶质的减少可能先于并导致肾脏浓缩功能缺陷，我们推测在蛋白质缺乏时可能会发生同样的机制。为了阐明蛋白质缺乏期间肾髓质有机渗透溶质与尿液浓缩缺陷之间的关系，我们研究了蛋白质营养不良对禁水或输注钠和/或尿素后有机渗透溶质含量的影响。禁水并没有使蛋白质缺乏大鼠的尿尿素、尿渗透压或组织钠和尿素恢复到对照水平。输注氯化钠仅增加了尿液和髓质中的钠。输注尿素增加了髓质中的尿素，但没有增加尿尿素。输注氯化钠加尿素仅增加了尿钠和尿素。无论使用何种高渗方案，蛋白质缺乏都会显著降低髓质中肌醇和牛磺酸的含量以及钠依赖性肌醇转运蛋白mRNA的水平。我们得出结论，除氯化钠和尿素外但与蛋白质摄入相关的因素是有机渗透溶质积累减少的原因。
