Green R, Giebisch G
Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06510.
Am J Physiol. 1989 Oct;257(4 Pt 2):F658-68. doi: 10.1152/ajprenal.1989.257.4.F658.
Simultaneous microperfusion of proximal tubules and peritubular capillaries in kidneys of rats anesthetized with Inactin was used to measure reflection coefficients. All perfusates contained cyanide to inhibit active transport; the tubular perfusate was isotonic and the peritubular capillaries were perfused with solutions made hypertonic with NaCl, NaHCO3, L-glucose, or sodium ferrocyanide. Measurements of recollected fluid enabled a precise mean gradient and ionic fluxes to be calculated; net water flux was measured with inulin. Imposed gradients always partly dissipated. Reflection coefficients were 0.59 +/- 0.01 for NaCl, 0.87 +/- 0.04 for NaHCO3-, and 0.96 +/- 0.07 for ferrocyanide, assuming that L-glucose was 1. Water permeability of the proximal tubule was 1,030 microns/s. Ionic permeability of Cl- (21.6 +/- 1.3 X 10(-5) cm/s) was greater than that for Na+ (13.3 +/- 2.7 X 10(-5) cm/s); permeability for L-glucose was 5.4 +/- 1.3 X 10(-5), and for ferrocyanide ions 2.7 +/- 0.9 X 10(-5) cm/s. It is concluded that in rat proximal tubule both NaCl and NaHCO3 have reflection coefficients less than 1.0 and solute asymmetry across the epithelium is a significant driving force for fluid reabsorption. Furthermore the data suggest that there is a significant contribution of solvent drag to solute movement.
采用对用硫喷妥钠麻醉的大鼠肾脏近端小管和肾小管周围毛细血管进行同步微量灌注的方法来测量反射系数。所有灌注液中均含有氰化物以抑制主动转运；肾小管灌注液为等渗液，而用NaCl、NaHCO₃、L - 葡萄糖或亚铁氰化钠制成的高渗溶液灌注肾小管周围毛细血管。对回收液体的测量使得能够精确计算平均梯度和离子通量；用菊粉测量净水通量。施加的梯度总是会部分消散。假设L - 葡萄糖的反射系数为1，则NaCl的反射系数为0.59±0.01，NaHCO₃⁻的反射系数为0.87±0.04，亚铁氰化物的反射系数为0.96±0.07。近端小管的水渗透率为1030微米/秒。Cl⁻的离子渗透率（21.6±1.3×10⁻⁵厘米/秒）大于Na⁺的离子渗透率（13.3±2.7×10⁻⁵厘米/秒）；L - 葡萄糖的渗透率为5.4±1.3×10⁻⁵，亚铁氰化物离子的渗透率为2.7±0.9×10⁻⁵厘米/秒。得出的结论是，在大鼠近端小管中，NaCl和NaHCO₃的反射系数均小于1.0，上皮细胞两侧的溶质不对称是液体重吸收的重要驱动力。此外，数据表明溶剂拖曳对溶质移动有显著贡献。
