Department of Cardiovascular Medicine, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, 277 West Yanta Road, 710061, Xi'an, Shaanxi, China.
J Comp Physiol B. 2010 Jan;180(1):117-24. doi: 10.1007/s00360-009-0391-z. Epub 2009 Jul 22.
To examine the effects of chronic ouabain treatment on blood pressure (BP), sodium excretion, and renal dopamine D(1) receptor level, male Sprague-Dawley (SD) rats were treated with ouabain (27.8 microg kg(-1) d(-1)) intraperitoneally for 5 weeks, and systolic blood pressure (SBP) were recorded weekly. After 5 weeks, sodium excretion and dopamine D(1) receptor agonist fenoldopam-mediated natriuresis were measured, and the expression and phosphorylation levels of the renal cortical dopamine D(1) receptor were confirmed by Western blot analysis. The effects of ouabain on fenoldopam-mediated inhibition of Na(+)-K(+)-ATPase activity were determined by colorimetric assays in human proximal tubular epithelial cells (HK-2 cells). After 5 weeks, the SBP in ouabain group was significantly higher than that in the control group (P < 0.01), but the sodium excretion and renal cortical D(1) receptor expression levels were reduced, and D(1) receptor phosphorylation levels were increased after ouabain treatment. Intravenous administration of fenoldopam caused an increased sodium excretion in control rats, but failed to induce natriuresis in ouabain-treated rats. In addition, fenoldopam induced a dose-respone (10(-9) to 10(-6) M) inhibition of Na(+)-K(+)-ATPase activity in HK-2 cells,but these effects were significantly diminished in HK-2 cells pretreated with nanomolar concentration of ouabain for 5 days (P < 0.01). We propose that the ouabain-induced reduction of the renal dopamine D(1) receptor function serves as a mechanism responsible for sodium retention, and this contributes to the hypertension induced by chronic ouabain treatment.
为了研究慢性哇巴因处理对血压（BP）、钠排泄和肾多巴胺 D1 受体水平的影响，雄性 Sprague-Dawley（SD）大鼠腹膜内给予哇巴因（27.8μg/kg/d）处理 5 周，每周记录收缩压（SBP）。5 周后，测量钠排泄和多巴胺 D1 受体激动剂芬氟拉明介导的利钠作用，并通过 Western blot 分析证实肾皮质多巴胺 D1 受体的表达和磷酸化水平。通过比色法测定哇巴因对人近端肾小管上皮细胞（HK-2 细胞）中芬氟拉明介导的抑制 Na+-K+-ATPase 活性的影响。5 周后，哇巴因组的 SBP 明显高于对照组（P<0.01），但钠排泄和肾皮质 D1 受体表达水平降低，哇巴因处理后 D1 受体磷酸化水平增加。静脉注射芬氟拉明可引起对照组大鼠钠排泄增加，但不能诱导哇巴因处理大鼠利钠作用。此外，芬氟拉明诱导 HK-2 细胞中 Na+-K+-ATPase 活性的剂量反应（10-9 至 10-6 M）抑制，但在预先用纳摩尔浓度哇巴因处理 5 天的 HK-2 细胞中，这些作用明显减弱（P<0.01）。我们提出，哇巴因诱导的肾多巴胺 D1 受体功能降低是钠潴留的机制，这有助于慢性哇巴因处理引起的高血压。
