Osmotic Membrane Stretch Increases Cytosolic Ca2+ and Inhibits Bone Resorption Activity in Rat Osteoclasts.

• Tsuzuki Takashi

  Department of Removable Prosthodontics, Fukuoka Dental College

• Okabe Koji

• Kajiya Hiroshi

• Habu Tetsuya

Bibliographic Information

Other Title

• Osmotic Membrane Stretch Increases Cytosolic Ca〔2+〕 and Inhibits Bone Resorption Activity in Rat Osteoclasts

Abstract

Although the importance of mechanical stress on bone metabolism is well known, the intracellular mechanisms involved are not well understood. To evaluate the role of mechanical stress on osteoclastic function, we investigated the effects of membrane stretch induced by osmotic cell swelling on cytosolic Ca²⁺ and bone resorption activity in freshly isolated rat osteoclasts. The intracellular Ca²⁺ concentration ([Ca²⁺]_i) was measured by fura-2 microspectrofluorimetry. Exposure to hypotonic solution (211–151 mOsm) caused cell swelling and reversibly increased [Ca²⁺]_i in the osteoclasts. This [Ca²⁺]_i increase was abolished by the omission of extracellular Ca²⁺<FONT FACE="TimesNewRomanPS">, but was not affected by the depletion of intracellular Ca²⁺ stores. Gd³⁺ and La³⁺ inhibited the swelling-induced [Ca²⁺]_i increase, while nifedipine and Bay K 8644 did not. Neither protein kinase A inhibitors (Rp-cAMP, H-89) nor protein kinase C inhibitors (staurosporine, chelerythrine) affected the [Ca²⁺]_i increase. Membrane depolarization was not essential for the [Ca²⁺]_i increase either. To assess the effects of membrane stretch on the bone resorption activity of osteoclasts, we investigated actin ring formation, the intracellular structure responsible for bone resorption in osteoclasts. Hypotonic stimulation acutely disrupted actin ring formation in an extracellular Ca²⁺-dependent manner, and this disruption was prevented by Gd³⁺. Moreover, Ca²⁺ ionophore (ionomycin) also induced disruption of the actin rings. These results indicate that mechanical stress inhibits osteoclastic bone resorption activity, possibly via the elevation of [Ca²⁺]_i through stretch-activated, non-selective cation channels.<br>

Journal

• The Japanese Journal of Physiology

  The Japanese Journal of Physiology 50 (1), 67-76, 2000

  THE PHYSIOLOGICAL SOCIETY OF JAPAN

Keywords

• osmotic cell swelling
• intracellular Ca<SUP>2+</SUP> concentration
• osteoclast
• actin ring
• bone resorption

Details

• CRID: 1390282680019623040
• NII Article ID: 130004435711
• NII Article ID: 10008290444
• NII Book ID: AA00691224
• DOI: 10.2170/jjphysiol.50.67
• COI: 1:CAS:528:DC%2BD3cXivFekt78%3D
• ISSN: 18811396
• ISSN: 0021521X
• NDL BIB ID: 5411015
• PubMed: 10866699
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I5411015
• Web Site: https://search.jamas.or.jp/link/ui/2001020144
• Text Lang: en
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • PubMed
  • CiNii Articles
• Abstract License Flag: Disallowed