Ernst S A, Schreiber J H
J Cell Biol. 1981 Dec;91(3 Pt 1):803-13. doi: 10.1083/jcb.91.3.803.
Na+,K+-ATPase was localized at the ultrastructural level in rat and rabbit kidney medulla. The cytochemical method for the K+-dependent phosphatase component of the enzyme, using p-nitrophenylphosphate (NPP) as substrate, was employed to demonstrate the distribution of Na+, K+-ATPase in tissue-chopped sections from kidneys perfusion-fixed with 1% paraformaldehyde-0.25% glutaraldehyde. In other outer medulla of rat kidney, ascending thick limbs (MATL) were sites of intense K+-dependent NPPase (K+-NPPase) activity, whereas descending thick limbs and collecting tubules were barely reactive. Although descending thin limbs (DTL) of short loop nephrons were unstained, DTL from long loop nephrons in outer medulla were sites of moderate K+-NPPase activity. In rat inner medulla, DTL and ascending thin limbs (ATL) were unreactive for K+-NPPase. In rabbit medulla, only MATL were sites of significant K+-NPPase activity. The specificity of the cytochemical localization of Na+,K+-ATPase at reactive sites in rat and rabbit kidney medulla was demonstrated by K+-dependence of reaction product deposition, localization of reaction product (precipitated phosphate hydrolyzed from NPP) to the cytoplasmic side of basolateral plasma membranes, insensitivity of the reaction to inhibitors of nonspecific alkaline phosphatase, and, in the glycoside-sensitive rabbit kidney, substantial inhibition of staining by ouabain. The observed pattern of distribution of the sodium transport enzyme in kidney medulla is particularly relevant to current models for urine concentration. The presence of substantial Na+,K+-ATPase in MATL is consistent with the putative role of this segment as the driving force for the countercurrent multiplication system in the outer medulla. The absence of significant activity in inner medullary ATL and DTL, however, implies that interstitial solute accumulation in this region probably occurs by passive processes. The localization of significant Na+,K+-ATPase in outer medullary DTL of long loop nephrons in the rat suggests that solute addition in this segment may occur in part by an active salt secretory mechanism that could ultimately contribute to the generation of inner medullary interstitial hypertonicity and urine concentration.
钠钾ATP酶在大鼠和兔肾髓质的超微结构水平上定位。采用以对硝基苯磷酸酯（NPP）为底物的该酶钾依赖性磷酸酶成分的细胞化学方法，来证明钠钾ATP酶在经1%多聚甲醛-0.25%戊二醛灌注固定的肾脏组织切片中的分布。在大鼠肾外髓质中，升支粗段（MATL）是钾依赖性NPP酶（K+-NPP酶）活性强烈的部位，而降支粗段和集合管几乎无反应。虽然短袢肾单位的降支细段（DTL）未染色，但外髓质中长袢肾单位的DTL是中度K+-NPP酶活性的部位。在大鼠内髓质中，DTL和升支细段（ATL）对K+-NPP酶无反应。在兔髓质中，只有MATL是显著K+-NPP酶活性的部位。大鼠和兔肾髓质中反应部位钠钾ATP酶细胞化学定位的特异性通过反应产物沉积的钾依赖性、反应产物（从NPP水解产生沉淀的磷酸盐）定位于基底外侧质膜的细胞质侧、反应对非特异性碱性磷酸酶抑制剂不敏感以及在对糖苷敏感的兔肾中哇巴因对染色的显著抑制来证明。在肾髓质中观察到的钠转运酶分布模式与当前的尿液浓缩模型特别相关。MATL中存在大量钠钾ATP酶与该节段作为外髓质逆流倍增系统驱动力的假定作用一致。然而，内髓质ATL和DTL中缺乏显著活性意味着该区域间质溶质的积累可能通过被动过程发生。大鼠长袢肾单位外髓质DTL中存在显著的钠钾ATP酶表明，该节段中溶质的添加可能部分通过主动盐分泌机制发生，这最终可能有助于内髓质间质高渗性的产生和尿液浓缩。
