A mathematical model of the rat proximal tubule.
A mathematical model of the rat proximal tubule.
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DOI：
10.1152/ajprenal.1986.250.5.f860
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发表时间：
1986-05
期刊：
影响因子：
--
通讯作者：
A. Weinstein
中科院分区：
文献类型：
--
作者：
A. Weinstein
利用质量守恒方程和电中性方程，将大鼠近端肾小管上皮的非平衡热力学模型推广到0.5厘米长的肾小管上皮。小管模型的输出包括管腔轮廓和由上皮模型产生的Na、K、Cl、HCO3、HPO4、H2PO4、葡萄糖和尿素的绝对近端重吸收。转运速率和通透性的选择与大鼠一致，导致管腔葡萄糖和碳酸氢盐的耗竭，并从电负性管腔过渡到正性管腔。尽管存在显著的跨上皮渗透驱动力(跨上皮葡萄糖梯度和氯-HCO3不对称)，上皮内溶质-溶剂耦合仍然是近端小管水重吸收的重要推动力。特别是，这意味着当在自由流动条件下出现的渗透梯度被用于计算上皮水渗透性时，将获得对该渗透性的显著高估。一个单一的一阶微分方程式已经与近端小管的近似非电解质模型结合在一起，该模型代表耦合和梯度驱动的水再吸收。在本工作中，该方程可以用综合管状模型准确地描述水的输运过程。
The equations of mass conservation and electroneutrality are used to extend a nonequilibrium thermodynamic model of the rat proximal tubule epithelium to a representation of a 0.5-cm segment of tubule. The output of the tubule model includes the luminal profiles and absolute proximal reabsorption of Na, K, Cl, HCO3, HPO4, H2PO4, glucose, and urea, generated by the epithelial model. Transport rates and permeabilities, chosen in agreement with those of the rat, result in luminal glucose and bicarbonate depletion and a transition from an electronegative to positive lumen. Despite the development of significant transepithelial osmotic driving forces (a transepithelial glucose gradient and Cl-HCO3 asymmetry), intraepithelial solute-solvent coupling remains an important force for water reabsorption along the proximal tubule length. In particular, this means that when osmotic gradients that appear under free-flow conditions are used in the calculation of the epithelial water permeability, a substantial overestimate of this permeability will be obtained. A single first-order differential equation has been derived in conjunction with an approximate nonelectrolyte model of the proximal tubule that represents both coupled and gradient-driven water reabsorption. In the present work, this equation is shown to yield an accurate description of water transport by the comprehensive tubule model.