Hwang S J, Haas M, Harris H W, Silva P, Yalla S, Sullivan M R, Otuechere G, Kashgarian M, Zeidel M L
Research Service, West Roxbury Department of Veterans Affairs Medical Center, Massachusetts 02132.
J Clin Invest. 1993 Jan;91(1):21-8. doi: 10.1172/JCI116173.
To characterize the sodium transport defect responsible for salt wasting in obstructive nephropathy, the major sodium transporters in the medullary thick ascending limb (mTAL), the apical Na-K-2Cl cotransporter and the basolateral Na-K-ATPase, were studied in fresh suspensions of mTAL cells and outer medulla plasma membranes prepared from obstructed and untreated kidneys. Oxygen consumption (QO2) studies in intact cells revealed marked reductions in the inhibitory effects of both furosemide and ouabain on QO2 in cells from obstructed, as compared with control animals, indicating a reduction in activities of both the Na-K-2Cl cotransporter and the Na-K-ATPase. Saturable [3H]bumetanide binding was reduced in membranes isolated from obstructed kidneys, but the Kd for [3H]bumetanide was unchanged, indicating a decrease in the number of functional luminal Na-K-2Cl cotransporters in obstructed mTAL. Ouabain sensitive Na-K-ATPase activity in plasma membranes was also reduced, and immunoblots using specific monoclonal antibodies directed against the alpha and beta subunits of rabbit Na-K-ATPase showed decreased amounts of both subunits in outer medullas of obstructed kidney. A significant decrease in [3H]bumetanide binding was detected after 4 h of ureteral obstruction, whereas Na-K-ATPase activity at this time was still not different from control. We conclude that ureteral obstruction reduces the amounts of both luminal Na-K-2Cl cotransporter and basolateral Na-K-ATPase in mTAL of obstructed kidney and that these reductions contribute to the salt wasting observed after release of obstruction.
为了明确梗阻性肾病中导致盐消耗的钠转运缺陷，我们研究了髓袢升支粗段（mTAL）中的主要钠转运体，即顶端Na-K-2Cl共转运体和基底外侧Na-K-ATP酶，研究对象为取自梗阻和未处理肾脏的mTAL细胞新鲜悬液以及外髓质质膜。对完整细胞的氧消耗（QO2）研究显示，与对照动物相比，呋塞米和哇巴因对梗阻动物细胞QO2的抑制作用显著降低，这表明Na-K-2Cl共转运体和Na-K-ATP酶的活性均降低。从梗阻肾脏分离的膜中，可饱和的[3H]布美他尼结合减少，但[3H]布美他尼的解离常数（Kd）未变，这表明梗阻的mTAL中功能性管腔Na-K-2Cl共转运体的数量减少。质膜中哇巴因敏感的Na-K-ATP酶活性也降低，使用针对兔Na-K-ATP酶α和β亚基的特异性单克隆抗体进行的免疫印迹显示，梗阻肾脏外髓质中这两种亚基的量均减少。输尿管梗阻4小时后检测到[3H]布美他尼结合显著减少，而此时Na-K-ATP酶活性仍与对照无差异。我们得出结论，输尿管梗阻会减少梗阻肾脏mTAL中管腔Na-K-2Cl共转运体和基底外侧Na-K-ATP酶的量，且这些减少导致了梗阻解除后观察到的盐消耗。
