title: A beta-actin isotype is present in rat cardiac endothelial cells but not in cardiac myocytes.
abstract: OBJECTIVE
  Active constriction in cardiac capillary endothelial cells (CCECs) is controversial. It is thought by many researchers that CCECs are not actively involved in constriction; others believe that these cells do contribute some of the force required for capillary constriction. Because actin is a major component of most contractile mechanisms responsible for changing cell shape, we compared two probes as potential monitors of actin distribution in CCECs in situ.
  
  
  METHODS
  We used SDS-PAGE, Western blotting, electron microscopy, conventional epifluorescence and confocal microscopy to evaluate an antibody against non-muscle beta-actin and fluorescently labeled phalloidin to detect actin in CCECs.
  
  
  RESULTS
  Fluorescently labeled phalloidin detected actin in cardiac muscle and faintly in CCECs. The antibody probe detected non-muscle beta-actin CCECs. However, this actin isotype did not occur in cardiac myocytes. In endothelial cells non-muscle beta-actin was concentrated at the cell periphery, and arranged as bundles of fibers, not as typical stress fibers.
  
  
  CONCLUSIONS
  Phalloidin is not suitable as a probe to monitor actin distribution in CCEC's in situ. The antibody is a potentially useful tool in monitoring the actin cytoskeleton and determining the capacity of CCECs for active vasoconstriction in vivo. Non-muscle beta-actin in CCECs is arranged in filament bundles which are not typical stress fibers.
authors.affiliation: Department of Molecular and Cellular Biology, St. Bartholomew's, London, UK.
authors.forename: M C
authors.initials: MC
authors.lastname: Glyn
authors.forename: B J
authors.initials: BJ
authors.lastname: Ward
mesh_terms: D000199:Actins / Q000032:analysis* / Q000276:immunology; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D015153:Blotting, Western; D002196:Capillaries / Q000737:chemistry / Q000166:cytology; D003331:Coronary Vessels / Q000737:chemistry* / Q000166:cytology; D004591:Electrophoresis, Polyacrylamide Gel; D004730:Endothelium, Vascular / Q000737:chemistry*; D005455:Fluorescent Antibody Technique; D005456:Fluorescent Dyes; D008297:Male; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009206:Myocardium / Q000737:chemistry*; D010590:Phalloidine; D020033:Protein Isoforms / Q000032:analysis* / Q000276:immunology; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000199:Actins; D000911:Antibodies, Monoclonal; D005456:Fluorescent Dyes; D020033:Protein Isoforms; D010590:Phalloidine