Am J Physiol. 1978 Jul;235(1):F1-11. doi: 10.1152/ajprenal.1978.235.1.F1.
Mechanisms for urinary concentration or dilution depend on counterflow processes, both tubular and vascular, within the renal medulla. Recently, there have emerged differing hypotheses about the renal tubular processes responsible for maintaining a hypertonic medullary interstitium. In this Editorial Review, R.W. Berliner frames three questions germane to this issue, and J.P. Kokko and D.J. Marsh provide their responses to these queries. The major issues addressed are: 1) What are the major unresolved question(s) concerning the mechanism by which concentrated urine is formed? 2) Current evidence suggests that the urea concentration in thin ascending limbs is slightly lower in the lumen than in interstitial fluid. Is the transepithelial concentration gradient between thin ascending limb and renal medullary interstitium sufficient to permit an entirely passive mechanism for diluting tubular fluid in the thin ascending limb? 3) A simple three-compartment model for the renal medullary concentrating process would include the tubular lumen, peritubular capillary, and the interstitium. Is it possible to generate a model that, by juxtaposing medullary structures, might explain renal medullary counterflow processes more adequately than the simple three-compartment model?
尿液浓缩或稀释的机制取决于肾髓质内肾小管和血管的逆流过程。最近，出现了关于负责维持高渗髓质间质的肾小管过程的不同假说。在这篇编辑评论中，R.W. 柏林纳提出了与该问题相关的三个问题，J.P. 科科和D.J. 马什对这些问题给出了他们的回答。所涉及的主要问题包括：1）关于浓缩尿形成机制的主要未解决问题是什么？2）目前的证据表明，细段升支管腔内的尿素浓度略低于间质液中的浓度。细段升支与肾髓质间质之间的跨上皮浓度梯度是否足以允许细段升支中肾小管液完全通过被动机制进行稀释？3）肾髓质浓缩过程的一个简单三室模型将包括肾小管腔、肾小管周围毛细血管和间质。是否有可能生成一个通过并列髓质结构，比简单三室模型更能充分解释肾髓质逆流过程的模型？
