We have previously shown the expression of the extracellular calcium (Cao 2+)-sensing receptor (CaR) in osteoblast-like cell lines, and others have documented its expression in sections of murine, bovine, and rat bone. The existence of the CaR in osteoblasts remains controversial, however, since some studies have failed to document its expression in the same osteoblast-like cell lines. The goals of the present study were twofold. 1) We sought to determine whether the CaR is expressed in the human osteoblast-like cell line, MG-63, which has recently been reported by others not to express this receptor.2) We investigated whether the CaR, if present in MG-63 cells, is functionally active, since most previous studies have not proven the role of the CaR in mediating known actions of Cao 2+ on osteoblast-like cells. We used immunocytochemistry and Western blotting with the specific, affinity-purified anti-CaR antiserum 4637 as well as Northern blot analysis and RT-PCR using a riboprobe and PCR primers specific for the human CaR, respectively, to show readily detectable CaR protein and mRNA expression in MG-63 cells. Finally, we employed the patch-clamp technique to show that an elevation in Cao 2+ as well as the specific, allosteric CaR activator NPS R-467 (0.5 μM), but not its less active stereoisomer NPS S-467 (0.5 μM), activate an outward K+ channel in MG-63 cells, strongly suggesting that the CaR in MG-63 cells is not only expressed but is functionally active.

  • G protein-coupled receptor
  • potassium channel
  • Northern analysis
  • reverse transcriptase-polymerase chain reaction
  • Western analysis
  • immunocytochemistry


  • Present address of T. Yamaguchi: Third Div., Dept. of Medicine, Kobe Univ. School of Medicine, Kobe 650-0017, Japan.

  • Address for reprint requests and other correspondence: E. M. Brown, Endocrine-Hypertension Div., Brigham and Women's Hospital, 221 Longwood Ave., Boston, MA 02115 (E-mail:embrown{at}rics.bwh.harvard.edu).

  • The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

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