Weinstein A M
Department of Physiology and Biophysics, Cornell University Medical College, New York, NY 10021, USA.
Exp Nephrol. 1998 Sep-Oct;6(5):462-8. doi: 10.1159/000020556.
Mathematical models of proximal tubule have been developed which represent the important solute species within the constraints of known cytosolic concentrations, transport fluxes, and overall epithelial permeabilities. In general, model simulations have been used to assess the quantitative feasibility of what appear to be qualitatively plausible mechanisms, or alternatively, to identify incomplete rationalization of experimental observations. The examples considered include: (1) proximal water reabsorption, for which the lateral interspace is a locus for solute-solvent coupling; (2) ammonia secretion, for which the issue is prioritizing driving forces - transport on the Na+/H+ exchanger, on the Na,K-ATPase, or ammoniagenesis; (3) formate-stimulated NaCl reabsorption, for which simple addition of a luminal membrane chloride/formate exchanger fails to represent experimental observation, and (4) balancing luminal entry and peritubular exit, in which ATP-dependent peritubular K+ channels have been implicated, but appear unable to account for the bulk of proximal tubule cell volume homeostasis.
已经开发出近端小管的数学模型，这些模型在已知胞质浓度、转运通量和整体上皮通透性的限制范围内，描绘了重要的溶质种类。一般来说，模型模拟已被用于评估在定性上看似合理的机制在定量方面的可行性，或者用于识别对实验观察结果解释不完整的情况。所考虑的例子包括：（1）近端水重吸收，其横向细胞间隙是溶质 - 溶剂偶联的位点；（2）氨分泌，其问题在于确定驱动力的优先级——通过钠/氢交换体、钠钾ATP酶进行的转运，还是氨生成；（3）甲酸盐刺激的氯化钠重吸收，简单地添加管腔膜氯/甲酸盐交换体无法解释实验观察结果；以及（4）平衡管腔进入和肾小管周围流出，其中涉及ATP依赖性肾小管周围钾通道，但似乎无法解释近端小管细胞体积稳态的大部分情况。
