Kim G H, Masilamani S, Turner R, Mitchell C, Wade J B, Knepper M A
Laboratory of Kidney and Electrolyte Metabolism, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Proc Natl Acad Sci U S A. 1998 Nov 24;95(24):14552-7. doi: 10.1073/pnas.95.24.14552.
Although the collecting duct is regarded as the primary site at which mineralocorticoids regulate renal sodium transport in the kidney, recent evidence points to the distal convoluted tubule as a possible site of mineralocorticoid action. To investigate whether mineralocorticoids regulate the expression of the thiazide-sensitive Na-Cl cotransporter (TSC), the chief apical sodium entry pathway of distal convoluted tubule cells, we prepared an affinity-purified, peptide-directed antibody to TSC. On immunoblots, the antibody recognized a prominent 165-kDa band in membrane fractions from the renal cortex but not from the renal medulla. Immunofluorescence immunocytochemistry showed TSC labeling only in distal convoluted tubule cells. Semiquantitative immunoblotting studies demonstrated a large increase in TSC expression in the renal cortex of rats on a low-NaCl diet (207 +/- 21% of control diet). Immunofluorescence localization in tissue sections confirmed the strong increase in TSC expression. Treatment of rats for 10 days with a continuous subcutaneous infusion of aldosterone also increased TSC expression (380 +/- 58% of controls). Furthermore, 7-day treatment of rats with an orally administered mineralocorticoid, fludrocortisone, increased TSC expression (656 +/- 114% of controls). We conclude that the distal convoluted tubule is an important site of action of the mineralocorticoid aldosterone, which strongly up-regulates the expression of TSC.
尽管集合管被认为是盐皮质激素调节肾脏钠转运的主要部位，但最近的证据表明远曲小管可能是盐皮质激素作用的部位。为了研究盐皮质激素是否调节噻嗪类敏感的Na-Cl共转运体（TSC）的表达，远曲小管细胞主要的顶端钠进入途径，我们制备了一种针对TSC的亲和纯化的肽导向抗体。在免疫印迹中，该抗体在肾皮质的膜组分中识别出一条明显的165-kDa条带，而在肾髓质中未识别出。免疫荧光免疫细胞化学显示TSC仅在远曲小管细胞中标记。半定量免疫印迹研究表明，低NaCl饮食（对照饮食的207±21%）的大鼠肾皮质中TSC表达大幅增加。组织切片中的免疫荧光定位证实了TSC表达的强烈增加。连续皮下注射醛固酮对大鼠进行10天治疗也增加了TSC表达（对照的380±58%）。此外，口服盐皮质激素氟氢可的松对大鼠进行7天治疗增加了TSC表达（对照的656±114%）。我们得出结论，远曲小管是盐皮质激素醛固酮的一个重要作用部位，醛固酮强烈上调TSC的表达。
