Velic Ana, Hirsch Jochen R, Bartel Jasmin, Thomas Regina, Schröter Rita, Stegemann Heike, Edemir Bayram, August Christian, Schlatter Eberhard, Gabriëls Gert
Medizinische Klinik und Poliklinik D, Experimentelle Nephrologie, Universitätsklinikum Münster, Domagkstrasse 3a, D-48149 Münster, Germany.
J Am Soc Nephrol. 2004 Apr;15(4):967-77. doi: 10.1097/01.asn.0000117287.74203.89.
Kidney transplantation often leads to disturbances of solute and volume maintenance in humans. To investigate underlying mechanisms, expression and function of renal transporters and receptors of the proximal tubule (PT) were analyzed in an acute rejection model of rat kidney transplantation. Semiquantitative RT-PCR and Western blot, histology, immunohistochemistry, and microfluorometry were performed on whole kidneys and isolated PT. With acute rejection, Na+/H+-exchanger type-3 (NHE-3) was markedly downregulated. Na+-HCO(3)(-)-cotransporter (NBC-1) and Na+-glucose transporter type-2 (SGLT2) were upregulated after transplantation. Expressions of Na+/H+-exchanger type-1 (NHE-1), Na+/K+-ATPase (NKA), angiotensin II (AngII) receptor (AT-1), or natriuretic peptide receptor (GC-A) were unaltered. Microfluorometric analyses of intracellular pH, Na+, and Ca2+ demonstrated a decrease in NHE-3 function and AngII-mediated stimulation of NHE-3. AngII-mediated inhibition of NHE-1 and function of all other transporters tested remained unaltered. Function of AT-1 and GC-A were unaffected. Reduced expression of NHE-3 was also confirmed by semiquantitative immunohistochemistry. These findings suggest that expression and function of transmembrane proteins involved in Na+-transport after transplantation and rejection is specifically modulated. The local renin-angiotensin-system is apparently not altered. Downregulation of NHE-3 may be a protective mechanism occurring in the graft.
肾移植常导致人体溶质和容量维持的紊乱。为研究其潜在机制，在大鼠肾移植急性排斥模型中分析了近端小管（PT）肾转运体和受体的表达及功能。对全肾和分离的PT进行了半定量RT-PCR、蛋白质印迹、组织学、免疫组织化学和微量荧光测定。急性排斥时，3型钠氢交换体（NHE-3）明显下调。移植后钠-碳酸氢根共转运体（NBC-1）和2型钠葡萄糖转运体（SGLT2）上调。1型钠氢交换体（NHE-1）、钠钾ATP酶（NKA）、血管紧张素II（AngII）受体（AT-1）或利钠肽受体（GC-A）的表达未改变。细胞内pH、钠和钙的微量荧光测定分析显示NHE-3功能降低以及AngII介导的NHE-3刺激作用。AngII介导的NHE-1抑制作用以及所有其他测试转运体的功能未改变。AT-1和GC-A的功能未受影响。半定量免疫组织化学也证实了NHE-3表达降低。这些发现表明，移植和排斥后参与钠转运的跨膜蛋白的表达和功能受到特异性调节。局部肾素-血管紧张素系统显然未改变。NHE-3的下调可能是移植物中发生的一种保护机制。
