Backman K A, Hayslett J P
Pflugers Arch. 1983 Mar;396(4):297-300. doi: 10.1007/BF01063934.
A capacity for both net potassium absorption and net potassium secretion has been demonstrated in the inner medullary collecting duct. The quantitative importance, however, of the inner medullary collecting duct in the regulation of urinary potassium in potassium deficiency, however has not been established. To assess the contribution of this segment to potassium conservation, microcatherization studies were performed in male Sprague-Dawley rats maintained either on a control diet or on a potassium free diet for 72 h. In control animals approximately 15% of the filtered load of potassium was excreted. Analysis of tubule fluid along the inner medullary collecting duct failed to demonstrate evidence of net potassium movement. Administration of a potassium free diet resulted in a marked reduction in potassium excretion to 0.3% of the filtered load. In contrast to control the inner medullary collecting duct of experimental animals absorbed nearly 90% of the amount of potassium entering this segment, since fractional delivery to the terminal portion of the nephron was about 2%. These data indicate that the inner medullary collecting duct makes a significant contribution to maximal renal conservation of potassium, since previous studies have shown that only 5 to 10% of filtered potassium is present in the late distal tubule of surface nephrons in animals on a low potassium intake.
髓质内集合管已被证明具有净钾吸收和净钾分泌的能力。然而，髓质内集合管在钾缺乏时对尿钾调节的定量重要性尚未确定。为了评估该节段对钾保留的作用，对雄性Sprague-Dawley大鼠进行了微插管研究，这些大鼠分别维持对照饮食或无钾饮食72小时。在对照动物中，约15%的滤过钾负荷被排泄。对沿髓质内集合管的小管液分析未能证明有净钾移动的证据。给予无钾饮食导致钾排泄显著减少至滤过负荷的0.3%。与对照相比，实验动物的髓质内集合管吸收了进入该节段钾量的近90%，因为输送到肾单位末端部分的钾分数约为2%。这些数据表明，髓质内集合管对肾脏最大程度的钾保留有显著贡献，因为先前的研究表明，低钾摄入动物的浅表肾单位远端小管晚期仅存在5%至10%的滤过钾。
