Regulation of cell volume by the osteosarcoma cell line UMR-106-01

M. Khademazad, B. X. Zhang, P. Loessberg, S. Muallem

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10 Scopus citations


Determination of cell volume by an electronic cell-sizing technique was used to study the role of ion transporters in cell volume regulation by the osteosarcoma cell line UMR-106-01. Swelling the cells in hypotonic medium was followed by regulatory volume decrease (RVD). The rate of RVD was strongly dependent on the subpassage used and increased with increasing subpassages. Swelling-evoked changes in cytosolic free Ca2+ ([Ca2+](i)) did not account for this behavior, since it was similar in cells from all subpassages. Increasing plasma membrane K+ permeability with valinomycin resulted in a similar rate of RVD in cells from different subpassages, suggesting increased K+ channel activity or other electrogenic transporter with increased subpassages. In contrast, the mechanisms responsible for regulatory volume increase (RVI) were fully active in cells from all subpassages. Increasing medium osmolarity of cells bathed in isotonic medium induced slow and incomplete RVI. In addition, shrinking cells exposed to hypotonic medium before completion of RVD resulted in impaired RVI. Effective RVI could be observed only after completion of RVD of cells exposed to hypotonic medium. Removal of extracellular Na+ or K+ completely blocked RVI, whereas removal of external Cl- partially blocked RVI. The effect of K+ removal probably reflects in part inhibition of Na-K-2Cl cotransport and in part inhibition of the Na+ pump. Furosemide inhibited RVI by ~70% while amiloride inhibited RVI by 25%. The combination of furosemide and amiloride almost completely blocked RVI. The dominant role of the Na-K-2Cl cotransporter in RVI in osteoblasts was further demonstrated by testing the effect of protein kinases on RVI. Inhibition of the cotransporter by activation of protein kinase C reduced RVI, whereas stimulation of the cotransporter by activation of protein kinase A increased RVI.

Original languageEnglish (US)
Pages (from-to)C441-C447
JournalAmerican Journal of Physiology - Cell Physiology
Issue number3 30-3
StatePublished - 1991


  • Amiloride
  • Furosemide
  • Subpassage
  • Volume regulatory decrease
  • Volume regulatory increase

ASJC Scopus subject areas

  • Physiology
  • Cell Biology


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