Kwon Tae-Hwan, Nielsen Jakob, Kim Young-Hee, Knepper Mark A, Frøkiaer Jørgen, Nielsen Søren
The Water and Salt Research Center, University of Aarhus, Denmark.
Am J Physiol Renal Physiol. 2003 Jul;285(1):F152-65. doi: 10.1152/ajprenal.00307.2002. Epub 2003 Mar 25.
The effect of ANG II treatment of rats for 7 days was examined with respect to the abundance and subcellular localization of key thick ascending limb (TAL) Na+ transporters. Rats were on a fixed intake of Na+ and water and treated with 0, 12.5, 25, 50 (ANG II-50), 100 (ANG II-100), and 200 (ANG II-200) ng x min(-1) x kg(-1) ANG II (sc). Semiquantitative immunoblotting revealed that Na+/H+ exchanger 3 (NHE3) abundance in the inner stripe of the outer medulla (ISOM) of ANG II-treated rats was significantly increased: 179 +/- 28 (ANG II-50, n = 5), 166 +/- 23 (ANG II-100, n = 7), and 167 +/- 19% (ANG II-200, n = 4) of control levels (n = 6, P < 0.05), whereas lower doses of ANG II were ineffective. The abundance of the bumetanide-sensitive Na(+)-K(+)-2Cl(-) cotransporter (BSC-1) in the ISOM was also increased to 187 +/- 28 (ANG II-50), 162 +/- 23 (ANG II-100), and 166 +/- 19% (ANG II-200) of control levels (P < 0.05), but there were no changes in the abundance of Na(+)-K(+)-ATPase and the electroneutral Na(+)-HCO3 cotransporter NBCn1. Immunocytochemistry confirmed the increase in NHE3 and BSC-1 labeling in medullary TAL (mTAL). In the cortex and the outer strip of the outer medulla, NHE3 abundance was unchanged, whereas immunocytochemistry revealed markedly increased NHE3 labeling of the proximal tubule brush border, suggesting subcellular redistribution of NHE3 or differential protein-protein interaction. Despite this, ANG II-treated rats (50 ng x min(-1) x kg(-1) for 5 days, n = 6) had a higher urinary pH compared with controls. NH4Cl loading completely blocked all effects of ANG II infusion on NHE3 and BSC-1, suggesting a potential role of pH as a mediator of these effects. In conclusion, increased abundance of NHE3 and BSC-1 in mTAL cells as well as increased NHE3 in the proximal tubule brush border may contribute to enhanced renal Na+ and HCO3 reabsorption in response to ANG II.
研究了血管紧张素II（ANG II）对大鼠连续治疗7天对关键厚升支（TAL）钠转运蛋白丰度和亚细胞定位的影响。大鼠固定摄入钠和水，并分别给予0、12.5、25、50（ANG II - 50）、100（ANG II - 100）和200（ANG II - 200）ng·min⁻¹·kg⁻¹的ANG II（皮下注射）。半定量免疫印迹显示，ANG II处理的大鼠外髓内层（ISOM）中钠氢交换体3（NHE3）的丰度显著增加：分别为对照组水平的179±28%（ANG II - 50，n = 5）、166±23%（ANG II - 100，n = 7）和167±19%（ANG II - 200，n = 4）（n = 6，P < 0.05），而较低剂量的ANG II无效。ISOM中布美他尼敏感的钠钾氯共转运体（BSC - 1）的丰度也增加到对照组水平的187±28%（ANG II - 50）、162±23%（ANG II - 100）和166±19%（ANG II - 200）（P < 0.05），但钠钾ATP酶和电中性钠 - 碳酸氢根共转运体NBCn1的丰度没有变化。免疫细胞化学证实了髓质TAL（mTAL）中NHE3和BSC - 1标记增加。在皮质和外髓外层，NHE3丰度未改变，而免疫细胞化学显示近端小管刷状缘的NHE3标记明显增加，提示NHE3的亚细胞重新分布或不同的蛋白质 - 蛋白质相互作用。尽管如此，ANG II处理的大鼠（50 ng·min⁻¹·kg⁻¹处理5天，n = 6）与对照组相比尿pH值更高。氯化铵负荷完全阻断了ANG II输注对NHE3和BSC - 1的所有作用，提示pH可能作为这些作用介导因子的潜在作用。总之，mTAL细胞中NHE3和BSC - 1丰度增加以及近端小管刷状缘NHE3增加可能有助于增强肾脏对ANG II的钠和碳酸氢根重吸收。
