Vehaskari V M, Hering-Smith K S, Klahr S, Hamm L L
Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri.
Kidney Int. 1989 Jul;36(1):89-95. doi: 10.1038/ki.1989.165.
To determine whether intrinsic changes in cortical collecting tubule (CCT) transport contribute to the maintenance of sodium and acid-base balance after loss of renal mass, we studied transport functions in isolated perfused CCT from rabbit remnant kidneys. The rabbits were sacrificed three weeks after surgical reduction of renal mass (by 3/4 to 7/8) at which time they were mildly azotemic but had no systemic electrolyte or acid-base disturbances. When perfused by standard methods in vitro, CCT from remnant kidneys exhibited sodium transport rates (lumen-to-bath 22Na-flux) approximately twice as high as those in CCT from control animals (111 +/- 19 vs. 54 +/- 7 pmol/min mm, P less than 0.02). A similar difference was present in the ouabain-sensitive sodium fluxes (81 +/- 16 vs. 39 +/- 8 pmol/min mm, P less than 0.05). In contrast, there were no significant differences in net bicarbonate transport. Significant hypertrophy of the remnant kidney CCT was reflected by 30 to 45% increases in tubule diameters. To examine the possible role of differences in food intake, we studied a separate group of weight-matched, pair-fed sham-operated and remnant kidney rabbits. Similar differences in total and ouabain-sensitive 22Na-flux, and in tubule size persisted in the pair-fed animals. A dissociation between active sodium transport and tubule hypertrophy was documented in the outer medullary collecting tubule: despite the lack of active sodium transport, hypertrophy was present. Our studies show that loss of renal mass results in a selective augmentation of certain transport processes in the CCT, implying selective or specific signals and mechanisms.
为了确定皮质集合管（CCT）转运的内在变化是否有助于肾单位减少后钠和酸碱平衡的维持，我们研究了来自兔残余肾的离体灌注CCT的转运功能。在手术减少肾单位（减少3/4至7/8）三周后处死兔子，此时它们有轻度氮质血症，但没有全身性电解质或酸碱紊乱。当在体外采用标准方法灌注时，残余肾的CCT表现出的钠转运速率（管腔至浴液的22Na通量）约为对照动物CCT的两倍（111±19对54±7 pmol/min·mm，P<0.02）。哇巴因敏感的钠通量也存在类似差异（81±16对39±8 pmol/min·mm，P<0.05）。相比之下，净碳酸氢盐转运没有显著差异。残余肾CCT明显肥大，表现为肾小管直径增加30%至45%。为了研究食物摄入量差异的可能作用，我们研究了另一组体重匹配、配对喂养的假手术和残余肾兔子。在配对喂养的动物中，总钠通量和哇巴因敏感的22Na通量以及肾小管大小仍存在类似差异。在外髓集合管中记录到了主动钠转运与肾小管肥大之间的分离：尽管缺乏主动钠转运，但仍存在肥大。我们的研究表明，肾单位减少导致CCT中某些转运过程的选择性增强，这意味着存在选择性或特异性的信号和机制。
