Intrinsic differences in various segments of the proximal convoluted tubule.
Intrinsic differences in various segments of the proximal convoluted tubule.
复制标题
近曲小管各段的内在差异。
DOI：
--
复制
发表时间：
1976
影响因子：
15.9
通讯作者：
J. Kokko
中科院分区：
文献类型：
--
作者：
H. Jacobson;J. Kokko
直到最近，还不可能直接比较表浅肾单位和近髓肾单位的功能。本研究采用体外微灌注技术，旨在研究浅浅肾元近曲小管段和近髓肾元之间是否存在功能差异。电生理研究表明，这些节段的相对氯离子和钠离子渗透率存在主要差异。近曲浅小管1 mm对钠的通透性大于对氯的通透性，近曲浅小管2 mm及以后各节段对氯的通透性大于对钠的通透性。发现髓旁近曲小管与浅曲小管在两个方面不同：第一，髓旁近曲小管各节段对氯离子和钠离子的相对渗透性没有差异；其次，对钠的渗透性始终大于对氯的渗透性。当灌注缺乏葡萄糖和氨基酸的溶液时，浅表和髓旁旋回表现出相同的经上皮电位变化，可逆降低至小于- 1 mV。因此，在这两个旋回中，似乎存在电致钠转运与这些有机溶质的转运耦合。这与这两种肾元的直肠部不同，后者显示出不依赖于有机溶质的电致钠转运。然而，当灌注缺乏葡萄糖和氨基酸但也含有高氯化物和低碳酸氢盐浓度的溶液时，表面卷积产生的正电位明显高于髓旁。这一差异反映了近端浅层褶积的相对氯离子渗透率较大。这些研究表明，从浅表和近髓肾元群中获得的近曲小管存在内在的功能差异。
Until recently it has not been possible to compare directly the function of superficial and juxtamedullary nephrons. The present studies, using in vitro microperfusion, were designed to examine whether functional differences exist between proximal convoluted tubule segments of superficial and juxtamedullary nephrons. Electrophysiological studies showed that major differences exist between the relative chloride and sodium permeabilities of these segments. In the 1st mm of the superficial proximal convoluted tubule, the permeability to sodium was greater than that to chloride, whereas in the 2nd mm of the superficial proximal convoluted tubule and all later segments, the permeability to chloride was greater than that to sodium. The juxtamedullary proximal convoluted tubule was found to differ from the superficial proximal convoluted tubule in two respects: first, the relative permeabilities to chloride and sodium did not differ in the various segments of the juxtamedullary proximal convoluted tubule; second, the permeability to sodium was greater than to chloride throughout. When perfused with a solution lacking glucose and amino acids, the superficial and juxtamedullary convolutions exhibited the same transepithelial potential change, a reversible decrease to less than -- 1 mV. It thus appears that in both convolutions there exists electrogenic sodium transport coupled to the transport of these organic solutes. This differs from pars recta of both of these nephrons, which have been shown to exhibit electrogenic sodium transport independent of organic solutes. However, when perfused with a solution lacking glucose and amino acids but also containing high chloride and low bicarbonate concentrations, the superficial convolution developed a significantly more positive potential than the juxtamedullary. This difference reflects greater relative chloride permeability in the superficial proximal convolution. These studies show that intrinsic functional differences exist between proximal convoluted tubules obtained from the superficial and juxtamedullary nephron populations.