Welling D J, Welling L W
Department of Pathology, University of Kansas Medical Center, Kansas City 66103.
Am J Physiol. 1988 Sep;255(3 Pt 2):F529-38. doi: 10.1152/ajprenal.1988.255.3.F529.
Isolated proximal renal tubules of rabbit reach a passive steady-state volume in isotonic medium after active transport is inhibited by ouabain or by inhibition of cellular metabolism or lack of metabolic substrates. If the tubules are then placed in a hypotonic NaCl medium they swell rapidly and then exhibit a volume regulatory decrease (VRD) similar to that seen when active transport is present. We have mathematically modeled these transient events by assuming that the basolateral cell membrane is permeated by pores having at least two distinct reflection coefficients with respect to sodium, potassium, and chloride. VRD depends on the difference of the values of the reflection coefficients of the pore types. As hydrostatic pressure is exerted by the stretching basement membrane, water and ions can be expelled from the cells across the lower reflection coefficient pores and cause VRD. When the hydrostatic pressure compliance is removed, the cells fail to volume decrease unless sufficient extracellular impermeant solute is present to provide an osmotic force for water and ion exit. We conclude that a heteroporous membrane may be an essential feature for cell volume regulation and maintenance.
在用哇巴因抑制主动转运、抑制细胞代谢或缺乏代谢底物后，兔的离体近端肾小管在等渗介质中达到被动稳态体积。如果随后将肾小管置于低渗氯化钠介质中，它们会迅速肿胀，然后表现出类似于存在主动转运时所见的体积调节性减少（VRD）。我们通过假设基底外侧细胞膜被对钠、钾和氯具有至少两种不同反射系数的孔所渗透，对这些瞬态事件进行了数学建模。VRD取决于孔类型反射系数值的差异。当拉伸的基底膜施加静水压力时，水和离子可通过较低反射系数的孔从细胞中排出并导致VRD。当去除静水压力顺应性时，除非存在足够的细胞外非渗透性溶质以提供水和离子流出的渗透压，否则细胞体积不会减少。我们得出结论，异质多孔膜可能是细胞体积调节和维持的一个基本特征。
