title: Isometric tension development and its calcium sensitivity in skinned myocyte-sized preparations from different regions of the human heart.
abstract: OBJECTIVE
  In this study we investigated whether differences exist or develop in patients with aortic or mitral valve disease in myofibrillar contractile function and contractile protein composition between subendo- and subepicardial human ventricular tissue. Isometric tension, its calcium sensitivity and contractile protein composition were studied in left ventricular subendo- and subepicardial and in atrial biopsies obtained during open heart surgery from 24 patients with mitral or aortic valve disease.
  
  
  METHODS
  Isometric tension was measured in mechanically isolated skinned myocyte-sized preparations at different free calcium concentrations at 15 degrees C. Protein composition was analysed by one-dimensional gel electrophoresis. A comparison was made between the results of subendo- and subepicardial ventricular tissue within each New York Heart Association class and within the different hemodynamically overloaded groups.
  
  
  RESULTS
  Maximal isometric tension was significantly lower in atrial than in ventricular preparations. The concentration of calcium required for half-maximal activation was significantly higher in atrial than in ventricular preparations. Within the ventricle no differences were found in contractile protein composition, isometric tension and its calcium sensitivity between subendo- and subepicardial tissue when all patients were treated as one group or when patients were subdivided according to severity of heart disease or hemodynamic overload.
  
  
  CONCLUSIONS
  In this group of patients with ventricular volume or pressure overload no regional differences exist or develop during cardiac disease in left ventricular myofibrillar protein composition and force production. Maximal isometric tension and its calcium sensitivity are smaller in atrial than in ventricular preparations.
authors.affiliation: Laboratory for Physiology, Free University, Amsterdam, Netherlands. J.van_der_Velden.physiol@med.vu.nl
authors.forename: J
authors.initials: J
authors.lastname: van der Velden
authors.forename: L J
authors.initials: LJ
authors.lastname: Klein
authors.forename: M
authors.initials: M
authors.lastname: van der Bijl
authors.forename: M A
authors.initials: MA
authors.lastname: Huybregts
authors.forename: W
authors.initials: W
authors.lastname: Stooker
authors.forename: J
authors.initials: J
authors.lastname: Witkop
authors.forename: L
authors.initials: L
authors.lastname: Eijsman
authors.forename: C A
authors.initials: CA
authors.lastname: Visser
authors.forename: F C
authors.initials: FC
authors.lastname: Visser
authors.forename: G J
authors.initials: GJ
authors.lastname: Stienen
mesh_terms: D000704:Analysis of Variance; D001021:Aortic Valve; D002118:Calcium / Q000378:metabolism*; D003285:Contractile Proteins / Q000032:analysis / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006325:Heart Atria / Q000378:metabolism; D006349:Heart Valve Diseases / Q000378:metabolism / Q000503:physiopathology*; D006352:Heart Ventricles / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007537:Isometric Contraction; D016014:Linear Models; D008297:Male; D008943:Mitral Valve; D009200:Myocardial Contraction; D009210:Myofibrils / Q000737:chemistry / Q000378:metabolism
chemical_list: D003285:Contractile Proteins; D002118:Calcium