Fine L G, Trizna W, Bourgoignie J J, Bricker N S
J Clin Invest. 1978 Jun;61(6):1508-18. doi: 10.1172/JCI109071.
An in vitro approach to the study of single nephron function in uremia has been employed in evaluating the control of fluid reabsorption by the renal superficial proximal straight tubule (PST). Isolated segments of PSTs from the remnant kidneys of uremic rabbits (stage III) were perfused in vitro and their rate of fluid reabsorption compared with normal PSTs and with PSTs derived from the remnant kidneys of nonuremic rabbits (stage II). All segments were exposed to a peritubular bathing medium of both normal and uremic rabbit serum thereby permitting a differentiation to be made between adaptations in function which are intrinsic to the tubular epithelium and those which are dependent upon a uremic milieu.Compared with normal and stage II PSTs, there was significant hypertrophy of the stage III tubules as evidenced by an increase in length and internal diameter, and a twofold increase in the dry weight per unit length. Fluid reabsorption per unit length of tubule was 70% greater in stage III than in normal and stage II PSTs, and was closely correlated with the increase in dry weight. Substitutions between normal and uremic rabbit serum in the peritubular bathing medium did not affect fluid reabsorption significantly in any of the three groups of PSTs. Perfusion of the tubules with an ultrafiltrate of normal vs. uremic serum likewise failed to influence the rate of net fluid reabsorption. It has previously been observed that net fluid secretion may occur in nonperfused or stop-flow perfused normal rabbit PSTs exposed to human uremic serum. Additional studies were thus performed on normal and stage III PSTs to evaluate whether net secretion occurs in the presence of rabbit uremic serum. No evidence for net secretion was found. These studies demonstrate that fluid reabsorption is greatly increased in the superficial PST of the uremic remnant kidney and that this functional adaptation is closely correlated with compensatory hypertrophy of the segment. Humoral factors in the peritubular environment do not appear to be important mediators of the enhanced fluid reabsorption.
一种用于研究尿毒症中单肾单位功能的体外方法已被用于评估肾浅表近端直小管（PST）对液体重吸收的控制。从尿毒症兔（III期）残余肾中分离出的PST节段进行体外灌注，并将其液体重吸收速率与正常PST以及来自非尿毒症兔（II期）残余肾的PST进行比较。所有节段均暴露于正常和尿毒症兔血清的肾小管周围浴液中，从而能够区分肾小管上皮固有的功能适应性变化和那些依赖于尿毒症环境的变化。与正常和II期PST相比，III期小管出现明显肥大，表现为长度和内径增加，单位长度干重增加两倍。III期小管每单位长度的液体重吸收比正常和II期PST高70%，且与干重增加密切相关。在肾小管周围浴液中用正常兔血清和尿毒症兔血清进行替换，对三组PST中的任何一组的液体重吸收均无显著影响。用正常血清与尿毒症血清的超滤液灌注小管同样未能影响净液体重吸收速率。此前已观察到，在暴露于人类尿毒症血清的未灌注或停流灌注的正常兔PST中可能发生净液体分泌。因此，对正常和III期PST进行了额外研究，以评估在存在兔尿毒症血清的情况下是否发生净分泌。未发现净分泌的证据。这些研究表明，尿毒症残余肾的浅表PST中液体重吸收显著增加，且这种功能适应性变化与该节段的代偿性肥大密切相关。肾小管周围环境中的体液因素似乎不是增强液体重吸收的重要介质。
