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Inhibition of Na + /Ca 2+ Exchange with KB‐R7943 or Bepridil Diminishes Mineral Deposition by Osteoblasts
Author(s) -
Stains Joseph P.,
Gay Carol V.
Publication year - 2001
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1359/jbmr.2001.16.8.1434
Subject(s) - bone sialoprotein , bepridil , osteoblast , chemistry , extracellular matrix , osteopontin , microbiology and biotechnology , medicine , bone cell , calcium , endocrinology , biochemistry , osteocalcin , biology , alkaline phosphatase , in vitro , verapamil , organic chemistry , enzyme
Osteoblasts form new bone by secreting a complex extracellular matrix that has the capacity to mineralize when adequate amounts of calcium and phosphate are supplied. The studies reported here show that long‐term treatment of cultured, primary osteoblasts with Na + /Ca 2+ exchanger (NCX) inhibitors, bepridil and KB‐R7943, impacts in a dose‐dependent manner the ability of the cells to form a calcified matrix. Treatment of confluent osteoblast cultures for 14 days with low levels of bepridil (3.0 μM) or KB‐R7943 (1.0 μM and 0.1 μM) resulted in a significantly diminished capacity of these cells to mineralize bone matrix, without significantly altering cell morphology, viability, or cell differentiation. The data indicate that inhibition of NCX reduces mineral accumulation in the bone matrix by blocking the efflux of Ca 2+ from the osteoblast into the bone fluid. In addition, immunocytochemistry of type I collagen (COLI) and bone sialoprotein (BSP) suggests that inhibition of NCX by 1.0 μM KB‐R7943 also may impair the secretion of bone matrix proteins by the osteoblasts. This study is the first to show that NCX is an important regulator of the bone fluid microenvironment and that NCX appears critical to the mineralization process.