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Calcified Tissue International

, Volume 72, Issue 3, pp 215–221 | Cite as

Modulation of Cytosolic Calcium Levels in Osteoblast-like Osteosarcoma Cells by Olpadronate and its Amino-Derivative IG-9402

  • G. Vazquez
  • G. Santillan
  • R. Boland
  • E. Roldán
  • A. Pérez-Lloret

The molecular mechanisms as well as the structure/activity relationships involved in the antiresorptive actions of bisphosphonates on bone cells are still not clear. Replacement of the R1-hydroxyl by an NH2 group in olpadronate (OPD) abolishes its antiresorptive activity. We show here that in the rat osteosarcoma-derived osteoblast-like ROS 17/2.8 cell line, OPD and IG-9402 (NH2-OPD; [3-(N,N-dimethylamine)-1-aminopropylidene bisphosphonate]), similar to 1,25(OH)2-vitamin D3, rapidly modulate cytosolic calcium levels ([Ca2+]i). As for the steroid hormone, the osteosarcoma cell Ca2+i response to OPD was rapid (30 sec) and sustained (>5 min), exhibiting a biphasic profile. The response to IG-9402 was also fast but smaller than that of OPD and 1,25(OH)2D3, and rapidly declined to levels near basal. The effect of these bisphosphonates on [Ca2+]i was dose-dependent, being maximal at 10?8 M and was not observed in non-bone cellular systems, e.g., skeletal muscle and breast cells. Pretreatment of the ROS 17/2.8 cells with the Ca2+ channel blockers nifedipine and verapamil markedly reduced (>70%) the influx phase of the response to OPD and almost completely inhibited that of IG-9402, indicating the participation of voltage-dependent Ca2+ channels in the action of both compounds. Moreover, preincubation with the phospholipase C inhibitors U73122 and neomycin or depletion of inner stores with thapsigargin completely blocked the response to either olpadronate or its amino-derivative. Both OPD and IG-9402 significantly increased osteocalcin release into the culture medium of osteosarcoma cells. The results support the involvement of the Ca2+ signaling pathway as part of the mechanism by which bisphosphonates induce bone cellular responses.

Keywords

Verapamil Osteosarcoma Nifedipine Bisphosphonates Osteocalcin 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag New York Inc. 2003

Authors and Affiliations

  • G. Vazquez
    • 1
  • G. Santillan
    • 1
  • R. Boland
    • 1
  • E. Roldán
    • 2
  • A. Pérez-Lloret
    • 2
  1. 1.Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, San Juan 670, (8000) Bahía Blanca, ArgentinaAR
  2. 2.Departamento de Farmacología Clínica, Gador S.A. Darwin 429, (1414) Buenos Aires, ArgentinaAR

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