Riccardi D, Hall A E, Chattopadhyay N, Xu J Z, Brown E M, Hebert S C
Renal Division, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2372, USA.
Am J Physiol. 1998 Mar;274(3):F611-22. doi: 10.1152/ajprenal.1998.274.3.F611.
We previously identified transcripts encoding a G protein-coupled, extracellular calcium/polyvalent cation-sensing receptor, RaKCaR, in rat kidney (D. Riccardi, J. Park, W.-S. Lee, G. Gamba, E. M. Brown, and S. C. Hebert. Proc. Natl. Acad. Sci. USA 92:131-135, 1994), which was proposed to provide the mechanism for modulating a variety of renal functions in response to changes in extracellular Ca2+ (E. M. Brown. In: Handbook of Physiology. Bethesda, MD: Am. Physiol. Soc., 1992, sect. 8, vol. 2, chapt. 39, p. 1841-1916; and S. C. Hebert. Kidney Int. 50: 2129-2139, 1996). Here, we examine the cellular and regional distribution of receptor protein by immunofluorescence microscopy using a polyclonal antibody raised against a 22 amino acid region of the NH2 terminus of the receptor. The most intense fluorescence was seen at the basolateral border of cortical thick ascending limb cells. Basolateral staining for the receptor was also detected in medullary thick ascending limbs, in macula densa cells identified by costaining with antibody to brain nitric oxide synthase, NOS-B1, and in distal convoluted tubule cells distinguished by costaining for the apical thiazide-sensitive Na(+)-Cl- cotransporter. Apical anti-RaKCaR staining was detected at the base of the brush border of proximal tubules with decreasing intensity from S1 to S3 segments. In cortical collecting ducts, anti-RaKCaR staining was detected in some, but not all, type A intercalated cells identified by costaining with anti-H(+)-ATPase and anti-AE1 Cl-/HCO3- exchanger antibodies. The present study demonstrates that RaKCaR protein is expressed in many different nephron segments and that the polarity of receptor expression varies with cell type along the nephron. These results suggest potential roles for the extracellular Ca2+/ polyvalent cation-sensing receptor in responding to both circulating and urinary concentrations of divalent minerals and potentially other polyvalent cations (e.g., aminoglycoside antibiotics) to modulate nephron function.
我们先前在大鼠肾脏中鉴定出了编码一种G蛋白偶联的细胞外钙/多价阳离子传感受体RaKCaR的转录本（D. Riccardi、J. Park、W.-S. Lee、G. Gamba、E. M. Brown和S. C. Hebert。《美国国家科学院院刊》92:131 - 135，1994年），该受体被认为提供了一种机制，可根据细胞外Ca2+的变化来调节多种肾脏功能（E. M. Brown。载于：《生理学手册》。马里兰州贝塞斯达：美国生理学会，1992年，第8节，第2卷，第39章，第1841 - 1916页；以及S. C. Hebert。《肾脏国际》50: 2129 - 2139，1996年）。在此，我们使用针对该受体NH2末端22个氨基酸区域产生的多克隆抗体，通过免疫荧光显微镜检查受体蛋白的细胞和区域分布。在皮质厚升支细胞的基底外侧边界观察到最强的荧光。在髓质厚升支、通过与脑一氧化氮合酶抗体NOS - B1共染色鉴定的致密斑细胞以及通过对顶端噻嗪敏感的Na(+) - Cl - 共转运体共染色区分的远曲小管细胞中也检测到了受体的基底外侧染色。在近端小管刷状缘底部检测到顶端抗RaKCaR染色，从S1段到S3段强度逐渐降低。在皮质集合管中，通过与抗H(+) - ATP酶和抗AE1 Cl-/HCO3 - 交换体抗体共染色鉴定，在一些但并非所有的A型闰细胞中检测到了抗RaKCaR染色。本研究表明RaKCaR蛋白在许多不同的肾单位节段中表达，并且受体表达的极性沿肾单位随细胞类型而变化。这些结果提示细胞外Ca2+/多价阳离子传感受体在响应循环和尿液中二价矿物质以及潜在的其他多价阳离子（如氨基糖苷类抗生素）浓度以调节肾单位功能方面可能发挥的作用。
