Impacts of Active Urea Secretion into Pars Recta on Urine Concentration and Urea Excretion Rate.
Impacts of Active Urea Secretion into Pars Recta on Urine Concentration and Urea Excretion Rate.
复制标题
直肠部活性尿素分泌对尿液浓度和尿素排泄率的影响。
DOI：
10.1002/phy2.34
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发表时间：
2013
影响因子：
2.5
通讯作者：
Bankir,Lise
中科院分区：
文献类型：
--
作者：
Layton,AnitaT;Bankir,Lise
实验观察到，早期远端肾小管尿素流量超过近曲小管向直肠部和亨利袢输送的尿素。此外，尿液中尿素的排泄分数可能超过与已知发生在皮质近曲小管中的重吸收相一致的值。对这些观察结果的一个可能的解释是，正如一些研究中提出的那样，尿素可能会主动分泌到直部中。然而，这一假设尚未得到实验证实。在本研究中，我们使用大鼠肾脏肾髓质的数学模型来研究活性尿素分泌对肾内尿素处理和尿液浓缩能力的影响。该模型仅代表外部和内部髓质区域，通过边界条件合并在皮质中发生的动作。模型脉管系统中的血流分为血浆室和红细胞室。我们比较了没有和有假设的直肠部活跃尿素分泌的尿素流速和其他相关模型变量。模拟表明，主动尿素分泌通过提高尿素排泄效率而诱导尿液浓缩能力的“尿素选择性”改善，而不需要更高的尿液流速，并且其他溶质的排泄仅发生适度变化。这些结果应该鼓励实验研究，以评估啮齿动物肾脏中活性尿素分泌的存在。
It has been observed experimentally that early distal tubular urea flow exceeds urea delivery by the proximal convoluted tubule to the pars recta and loop of Henle. Moreover, the fractional excretion of urea in the urine may exceed values compatible with the reabsorption known to occur in the proximal convoluted tubule in the cortex. A likely explanation for these observations is that urea may be actively secreted into the pars recta, as proposed in a few studies. However, this hypothesis has yet to be demonstrated experimentally. In this study, we used a mathematical model of the renal medulla of the rat kidney to investigate the impacts of active urea secretion in the intrarenal handling of urea and in the urine concentrating ability. The model represents only the outer and inner medullary zones, with the actions taking place in the cortex incorporated via boundary conditions. Blood flow in the model vasculature is divided into plasma and red blood cell compartments. We compared urea flow rates and other related model variables without and with the hypothetical active urea secretion in the pars recta. The simulation suggests that active urea secretion induces a “urea‐selective” improvement in urine concentrating ability by enhancing the efficiency of urea excretion without requiring a higher urine flow rate, and with only modest changes in the excretion of other solutes. These results should encourage experimental studies in order to assess the existence of an active urea secretion in the rodent kidney.