Analysis of microvascular water and solute exchanges in the renal medulla.
Analysis of microvascular water and solute exchanges in the renal medulla.
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肾髓质微血管水和溶质交换的分析。
DOI：
10.1152/ajprenal.1984.247.2.f303
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
Deen,WM
中科院分区：
文献类型：
--
作者：
Pallone,TL;Morgenthaler,TI;Deen,WM
建立了一个理论模型来模拟正常缺水大鼠骨髓微循环中的溶质和水的运输。该模型由一个下行血管单位(DVR)和几个上升血管单位(AVR)组成，从皮质髓质交界处延伸到乳头顶端。稳态质量平衡将氯化钠、尿素和血浆蛋白浓度的梯度以及血浆和红细胞流速的变化与直肠血管和红细胞的通透性特性联系起来。与以前的模型不同，假设DVR和AVR中都存在跨壁体积通量。现有的微穿测量表明，DVR在内髓内的净体积去除与DVR中的氯化钠反射系数在0.10和0.80之间是一致的。DVR的水力渗透率估计大于0.18×10(-6)厘米×S-1×毫米汞-1。根据目前可获得的数据，AVR的水力渗透率还不能被设定可靠的界限。据预测，血管单位将完成对内髓间质中氯化钠和水的大量净清除，但对尿素的清除相对较少。发现离开AVR内髓质的红细胞轻微脱水。据计算，在给定的血流速度下，初始骨髓红细胞压积越低，血管单位排出水分的效果就越好。文中还讨论了几个未解决的问题，包括连接DVR和AVR的毛细血管丛的作用。在DVR以外的结构中，暴露的乳头中观察到的体积摄取发生在毛细血管丛而不是AVR中，AVR水力通透性的估计值降低，正如预测的由内髓中的血管单位总的体积摄取一样。
A theoretical model has been developed to simulate solute and water transport in the medullary microcirculation of the normal hydropenic rat. The model is formulated in terms of a countercurrent vascular unit consisting of one descending (DVR) and several ascending vasa recta (AVR) extending from the corticomedullary junction to the tip of the papilla. Steady-state mass balances relate gradients in NaCl, urea, and plasma protein concentrations and variations in the flow rates of plasma and red blood cells to permeability properties of the vasa recta and erythrocytes. In contrast to previous models, transmural volume fluxes are assumed to be present in both DVR and AVR. Available micropuncture measurements suggesting net volume removal from DVR within the inner medulla are found to be consistent with NaCl reflection coefficients in DVR between 0.10 and 0.80. The hydraulic permeability in the DVR is estimated to be greater than 0.18 X 10(-6) cm X s-1 X mmHg-1. Based on currently available data, reliable bounds cannot yet be placed on the hydraulic permeability of the AVR. The vascular unit is predicted to accomplish substantial net removal of NaCl and water from the inner medullary interstitium but relatively little removal of urea. Red cells leaving the inner medulla in the AVR are found to be slightly dehydrated. It is calculated that at a given blood flow rate, the lower the initial medullary hematocrit, the more effective the vascular unit is at removing water. Several unresolved issues are discussed, including the role of the capillary plexus that joins DVR with AVR. To the extent that the volume uptake observed in the exposed papilla in structures beyond the DVR occurs in the capillary plexus and not in the AVR, estimated values of AVR hydraulic permeability are reduced, as is predicted overall volume uptake by the vascular unit in the inner medulla.