Garg L C, Mackie S, Tisher C C
Pflugers Arch. 1982 Aug;394(2):113-7. doi: 10.1007/BF00582911.
Na-K-ATPase activity was determined in 10 segments of the rat nephron using a fluorometric microassay method [4]. The enzyme activity showed three peaks (greater than 200 pmol ADP min-1 mm-1) along the nephron of normal rats. These peaks were in the S1 portion of the proximal tubule, the medullary thick ascending limb from the inner stripe and the distal convoluted tubule. Feeding the rats a low potassium diet for 8 weeks produced a significant decrease in Na-K-ATPase activity in the cortical collecting duct, but no significant change in this enzyme in any other segment. The low potassium diet did not produce a significant change in Mg-ATPase in any nephron segments. We conclude that Na-K-ATPase activity along the rat nephron shows a pattern that is qualitatively similar to that seen in the rabbit nephron [4]. However, quantitatively the Na-K-ATPase activity in the rat nephron is greater than in the corresponding segments of the rabbit nephron. The results are consistent with the greater rate of glomerular filtration and Na+ reabsorption per rat nephron. Furthermore, our results suggest that the decrease in potassium excretion during potassium deficiency is modulated, at least in part, by the level of Na-K-ATPase activity in the cortical collecting duct.
采用荧光微量测定法[4]测定了大鼠肾单位10个节段的钠钾ATP酶活性。在正常大鼠的肾单位中，该酶活性沿肾单位呈现三个峰值（大于200 pmol ADP min-1 mm-1）。这些峰值分别位于近端小管的S1段、内髓质带的髓袢升支粗段和远曲小管。给大鼠喂食低钾饮食8周后，皮质集合管中的钠钾ATP酶活性显著降低，但其他节段的该酶活性无显著变化。低钾饮食对任何肾单位节段的镁ATP酶均未产生显著影响。我们得出结论，大鼠肾单位的钠钾ATP酶活性模式在质量上与兔肾单位相似[4]。然而，从数量上看，大鼠肾单位的钠钾ATP酶活性高于兔肾单位相应节段。这些结果与每只大鼠肾单位更高的肾小球滤过率和钠重吸收率一致。此外，我们的结果表明，缺钾期间钾排泄的减少至少部分受皮质集合管中钠钾ATP酶活性水平的调节。
