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Horm Metab Res 2004; 36(1): 22-26
DOI: 10.1055/s-2004-814196
Original Basic
© Georg Thieme Verlag Stuttgart · New York

Extracellular Calcium Increases Free Cytoplasmic Calcium and DNA Synthesis in Human Osteoblasts

J.  A.  Tsai1 , E.  Bucht2 , O.  Torring3 , H.  Kindmark4
  • 1Karolinska Institutet, Center for Surgical Sciences, Department of Surgery, Huddinge University Hospital, Stockholm, Sweden
  • 2Karolinska Institutet, Department of Molecular Medicine, Endocrine and Diabetes Unit, Karolinska Hospital, Stockholm, Sweden
  • 3Karolinska Institutet, Department of Medicine, Division of Endocrinology, Södersjukhuset, Stockholm, Sweden
  • 4Department of Medical Sciences, Endocrine Oncology Unit, University Hospital, Uppsala, Sweden
Further Information

Publication History

Received 11 February 2003

Accepted after revision 10 July 2003

Publication Date:
25 February 2004 (online)

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Abstract

A high concentration of extracellular calcium (8 mM) induced an increase in free cytoplasmic calcium, a lower cyclic AMP level and increased DNA synthesis in primary cultures of human osteoblast-like cells. Inhibition of protein kinase C with bisindolylmaleimide I inhibited the stimulatory effect of extracellular calcium on DNA synthesis in human osteoblast-like cells, whereas inhibition of protein kinase A with Rp-cAMPs had no effect on DNA synthesis. This indicates that protein kinase C, possibly via increased free cytoplasmic calcium, mediates the effect of extracellular calcium on DNA synthesis in osteoblast-like cells rather than a relative decrease in cyclic AMP and protein kinase A activity. Furthermore, a low concentration (0.5 mM) of extracellular calcium decreased DNA synthesis. In conclusion, these data suggest that a high extracellular calcium level may be a coupling factor that recruits osteoblasts in the bone remodeling process, and that a low level of extracellular calcium may also regulate osteoblast function.

Key words

Cyclic AMP · Protein kinase C · Protein kinase A · Magnesium · Gadolinium

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E. Bucht,Ph. D. 

Department of Molecular Medicine, Endocrine and Diabetes Unit ·

Karolinska Hospital · 171 76 Stockholm · Sweden

Phone: + 46 (8) 51 77 23 94

Fax: + 46 (8) 51 77 67 92 ·

Email: elisabet.bucht@molmed.ki.se