Brenner B M, Falchuk K H, Keimowitz R I, Berliner R W
J Clin Invest. 1969 Aug;48(8):1519-31. doi: 10.1172/JCI106118.
The relationship between peritubular capillary protein concentration and rate of sodium reabsorption by the rat proximal tubule was examined using free-flow recollection micropuncture techniques. Tubule fluid-to-plasma inulin ratios were measured before, during, and at successive intervals after brief (15-25 sec) intra-aortic injections (at the level of the renal artery) of colloid-free, isoncotic, and hyperoncotic solutions. Arterial hematocrit and protein concentrations were measured simultaneously in these rats. In other rats, total protein concentration of peritubular capillary blood plasma was determined before, during, and after these same infusions with a newly described submicroliter fiber-optic colorimeter. In the 15-25 sec interval necessary to infuse 2 ml of these test solutions, fractional and absolute sodium reabsorption varied directly with peritubular capillary colloid osmotic pressure, declining during infusion of colloid-free solutions, increasing during hyperoncotic infusions, and remaining unchanged during isoncotic infusions. In the subsequent 20-min interval after intra-aortic injection of these test solutions, capillary protein concentration remained at (isoncotic infusions) or returned to (colloid-free and hyperoncotic fluids) control values. Whereas reabsorption after colloid-free solutions returned to base line levels in parallel with the return in capillary protein concentration, after colloid infusions (which resulted in continued expansion of extracellular fluid volume), a progressive decline in reabsorption was observed. These results afford strong evidence that peritubular capillary colloid osmotic pressure is one important determinant of proximal sodium reabsorption. Nevertheless it is apparent that mechanisms other than or in addition to this must be invoked to explain the delayed inhibition of reabsorption that accompanies expansion of extracellular fluid volume by colloid solutions.
采用自由流回收微穿刺技术，研究了大鼠近端小管周毛细血管蛋白浓度与钠重吸收率之间的关系。在经主动脉（肾动脉水平）短暂（15 - 25秒）注射无胶体、等渗和高渗溶液之前、期间及之后的连续时间段，测量小管液与血浆中菊粉的比率。同时测定这些大鼠的动脉血细胞比容和蛋白质浓度。在其他大鼠中，使用一种新描述的亚微升光纤比色计，在相同输注之前、期间和之后，测定小管周毛细血管血浆的总蛋白浓度。在输注2毫升这些测试溶液所需的15 - 25秒间隔内，钠的分数重吸收和绝对重吸收与小管周毛细血管胶体渗透压直接相关，在输注无胶体溶液时下降，在输注高渗溶液时增加，在输注等渗溶液时保持不变。在经主动脉注射这些测试溶液后的随后20分钟间隔内，毛细血管蛋白浓度保持在（等渗输注）或恢复到（无胶体和高渗液体）对照值。无胶体溶液输注后，重吸收随着毛细血管蛋白浓度的恢复而平行回到基线水平，而胶体输注后（导致细胞外液体积持续扩张），观察到重吸收逐渐下降。这些结果提供了有力证据，表明小管周毛细血管胶体渗透压是近端钠重吸收的一个重要决定因素。然而，显然必须援引除此以外或与之相关的机制来解释胶体溶液导致细胞外液体积扩张时伴随的重吸收延迟抑制现象。
