Goldsmith D I, Drukker A, Blaufox M D, Edelmann C M, Spitzer A
Am J Physiol. 1979 Nov;237(5):F392-7. doi: 10.1152/ajprenal.1979.237.5.F392.
It is generally recognized that developing animals retain sodium due to an enhanced reabsorption in distal tubule segements, even when the amount administered is in excess of their needs. This study was designed to test the relationship between this relative inability to dispose of a saline load and the functional characteristics of the kidney during postnatal maturation. In addition, we explored the role played by some of the factors known to affect natriuresis in the adult subject. Measurements of sodium excretion, glomerular filtration rate (GFR), and renal blood flow (RBF) and its intrarenal distribution were made in three age groups of puppies and in adult dogs. During expansion the GFR rose rapidly and to a similar extent at all ages, but it fell thereafter, the rate of decline being much slower in adult than in developing animals (P less than 0.001). RBF and its intrarenal distribution were not altered by volume expansion. The degree of natriuresis did not reflect either the age-related or the expansion-induced changes in GFR. Fractional and absolute sodium excretion were substantially higher in 2-wk-old puppies than in either 1- or 3-wk-old animals (P less than 0.002). These findings demonstrate that the blunted renal response of the maturing animal to saline loading is due to the persistence of an enhanced tubular reabsorption rather than to a limitation in glomerular filtration.
一般认为，发育中的动物由于远曲小管段重吸收增强而潴留钠，即使给予的量超过其需要量。本研究旨在测试这种相对无法处理盐负荷与出生后成熟过程中肾脏功能特征之间的关系。此外，我们探讨了一些已知影响成年个体利钠的因素所起的作用。对幼犬的三个年龄组和成年犬进行了钠排泄、肾小球滤过率（GFR）、肾血流量（RBF）及其肾内分布的测量。在扩容期间，GFR迅速上升且在所有年龄组中上升幅度相似，但此后下降，成年动物的下降速度比发育中的动物慢得多（P小于0.001）。RBF及其肾内分布不受容量扩张的影响。利钠程度既不反映与年龄相关的GFR变化，也不反映扩容引起的GFR变化。2周龄幼犬的分数钠排泄和绝对钠排泄显著高于1周龄或3周龄动物（P小于0.002）。这些发现表明，成熟动物对盐负荷的肾脏反应迟钝是由于肾小管重吸收增强持续存在，而不是由于肾小球滤过受限。
