title: Left ventricular length dependent activation in the isovolumetric rat heart.
abstract: OBJECTIVE
  The aim of the study was to examine, in a whole heart preparation, the relationship between length changes in cardiac muscle and tension development and length dependent activation.
  
  
  METHODS
  Rat hearts were perfused by the Langendorff technique and isovolumetric pressure changes in the left ventricle, produced by increasing diastolic pressures (0, 5, 10, 15, 20, 25 mm Hg), were studied at different calcium concentrations (0.5, 1.25, 2.5, 3.75 mmol.litre-1).
  
  
  METHODS
  20 whole heart preparations were obtained from albino rats of either sex, weight 180-240 g (females) and 220-330 g (males).
  
  
  RESULTS
  In a comparison of ventricular diastolic upsilon systolic pressure curves, normalised with respect to maximum isovolumetric systolic pressure, there was a separation and an upward displacement of the curves with increments in calcium concentration in the perfusate.
  
  
  CONCLUSIONS
  The results show, as in isolated preparations, that there is length dependent activation in the whole rat heart.
authors.affiliation: Departamento de Ciências Fisiológicas, Universidade Federal do Espirito Santo, Vitória, Brasil.
authors.forename: I
authors.initials: I
authors.lastname: Stefanon
authors.forename: D V
authors.initials: DV
authors.lastname: Vassallo
authors.forename: J G
authors.initials: JG
authors.lastname: Mill
mesh_terms: D000818:Animals; D001699:Biometry; D001794:Blood Pressure / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006321:Heart / Q000033:anatomy & histology / Q000502:physiology*; D006352:Heart Ventricles; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology*; D051381:Rats
chemical_list: D002118:Calcium