title: Myocardial remodeling after large infarcts in rat converts post rest-potentiation in force decay.
abstract: BACKGROUND
  Post-rest contraction (PRC) of cardiac muscle provides indirect information about the intracellular calcium handling.
  
  
  OBJECTIVE
  Our aim was to study the behavior of PRC, and its underlying mechanisms, in rats with myocardial infarction.
  
  
  METHODS
  Six weeks after coronary occlusion, the contractility of papillary muscles (PM) obtained from sham-operated (C, n=17), moderate infarcted (MMI, n=10) and large infarcted (LMI, n=14) rats was evaluated, following rest intervals of 10 to 60 seconds before and after incubation with lithium chloride (Li(+)) substituting sodium chloride or ryanodine (Ry). Protein expression of SR Ca(2+)-ATPase (SERCA2), Na(+)/Ca(2+) exchanger (NCX), phospholamban (PLB) and phospho-Ser(16)-PLB were analyzed by Western blotting.
  
  
  RESULTS
  MMI exhibited reduced PRC potentiation when compared to C. Opposing the normal potentiation for C, post-rest decays of force were observed in LMI muscles. In addition, Ry blocked PRC decay or potentiation observed in LMI and C; Li(+) inhibited NCX and converted PRC decay to potentiation in LMI. Although MMI and LMI presented decreased SERCA2 (72±7% and 47±9% of Control, respectively) and phospho-Ser(16)-PLB (75±5% and 46±11%, respectively) protein expression, overexpression of NCX (175±20%) was only observed in LMI muscles.
  
  
  CONCLUSIONS
  Our results showed, for the first time ever, that myocardial remodeling after MI in rats may change the regular potentiation to post-rest decay by affecting myocyte Ca(2+) handling proteins.
authors.affiliation: Departamento de Medicina, Divisão de Cardiologia, Universidade Federal de São Paulo, Brazil. bocalini@fcr.epm.br
authors.forename: Danilo Sales
authors.initials: DS
authors.lastname: Bocalini
authors.forename: Leonardo
authors.initials: L
authors.lastname: dos Santos
authors.forename: Ednei Luiz
authors.initials: EL
authors.lastname: Antonio
authors.forename: Alexandra Alberta dos
authors.initials: AA
authors.lastname: Santos
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Davel
authors.forename: Luciana V
authors.initials: LV
authors.lastname: Rossoni
authors.forename: Dalto Valentim
authors.initials: DV
authors.lastname: Vassalo
authors.forename: Paulo José Ferreira
authors.initials: PJ
authors.lastname: Tucci
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D004195:Disease Models, Animal; D018021:Lithium Chloride / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects* / Q000502:physiology; D009203:Myocardial Infarction / Q000145:classification / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism; D010210:Papillary Muscles / Q000378:metabolism; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D012433:Ryanodine / Q000494:pharmacology; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*; D020257:Ventricular Remodeling / Q000502:physiology*; D000099211:Phospholamban
chemical_list: D002118:Calcium; D002135:Calcium-Binding Proteins; D018021:Lithium Chloride; D012433:Ryanodine; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D019831:Sodium-Calcium Exchanger; D000099211:Phospholamban; C506948:Atp2a2 protein, rat