title: Hypo-osmotic stress induces calcium-dependent actin reorganization in articular chondrocytes.
abstract: OBJECTIVE
  The aim of this study was to investigate the effects of hypo-osmotically induced calcium (Ca(2+)) transients on the organization of the actin cytoskeleton in articular chondrocytes. The secondary hypothesis tested was that actin restructuring following hypo-osmotic stress is mediated by gelsolin.
  
  
  METHODS
  Isolated porcine chondrocytes were exposed to hypo-osmotic stress, and [Ca(2+)](i)was monitored using laser scanning microscopy. Calcium transients were monitored using fluorescent ratiometric imaging. The intracellular distribution of actin was examined using fluorescent immunohistochemistry and transient transfection with the pEGFP-actin plasmid. The intracellular distribution of gelsolin was investigated using fluorescent immunohistochemistry.
  
  
  RESULTS
  Osmotic stress induced transient increases in [Ca(2+)](i)caused reorganization of intracellular actin through a mechanism that required Ca(2+)in the extracellular media. Fluorescence microscopy revealed that gelsolin was colocalized with F-actin immediately following hypo-osmotic stress but dissociated over time.
  
  
  CONCLUSIONS
  These results indicate that hypo-osmotic stress induces a gelsolin-mediated reorganization of actin through a transient increase in [Ca(2+)](i).
authors.affiliation: Orthopaedic Research Laboratories, Department of Surgery, Duke University Medical Center, 27710, Durham,NC, USA
authors.forename: G R
authors.initials: GR
authors.lastname: Erickson
authors.forename: D L
authors.initials: DL
authors.lastname: Northrup
authors.forename: F
authors.initials: F
authors.lastname: Guilak
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000493:pharmacokinetics*; D002358:Cartilage, Articular / Q000378:metabolism*; D019902:Chondrocytes / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D018260:Gelsolin / Q000378:metabolism; D049452:Green Fluorescent Proteins; D007202:Indicators and Reagents; D015544:Inositol 1,4,5-Trisphosphate / Q000032:analysis; D008164:Luminescent Proteins; D018613:Microscopy, Confocal; D009995:Osmosis / Q000502:physiology; D013552:Swine
chemical_list: D000199:Actins; D018260:Gelsolin; D007202:Indicators and Reagents; D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium