title: Hypertrophied myocardium is more dependent on extracellular calcium than the normal cardiac muscle.
abstract: BACKGROUND
  The aim of this study was to analyze stable hypertrophied myocardial function and its response to inotropic maneuvers in rats submitted to renovascular hypertension for a 10-week period (RHT group, n=10).
  
  
  METHODS
  Myocardial performance was studied in isolated left ventricle papillary muscles in isometric contraction under the following conditions: at postrest contraction of 30 seconds (PRC), at extracellular calcium (ECa2+) chloride concentration of 1.25 and 5.20 mM, and after beta-adrenergic stimulation with 10-6 M isoproterenol (ISOP).
  
  
  RESULTS
  The results were compared with normotensive Wistar controls rats (C group, n=10). In basal condition, resting tension, and contraction time (TPT) were greater, while relaxation time (RT50) tended to be longer in RHT than C group. PRC and ISOP promoted a similar change in muscle function response intensity (delta) in both groups. ECa2+ shift did not change TPT in the C group and decreased TPT in the RHT animals; delta was different between these groups. RT50 increased in C and decreased in RHT, both without statistical significance; however, delta was different.
  
  
  CONCLUSIONS
  These results suggest that hypertrophied myocardial dysfunction may be attributed to changes in intracellular calcium cycling.
authors.affiliation: Botucatu Medical School, UNESP-São Paulo State University, Botucatu, Brazil.
authors.forename: Reginaldo
authors.initials: R
authors.lastname: de Barros
authors.forename: Leonardo A M
authors.initials: LA
authors.lastname: Zornoff
authors.forename: Henrique B
authors.initials: HB
authors.lastname: Ribeiro
authors.forename: Marina P
authors.initials: MP
authors.lastname: Okoshi
authors.forename: Carlos R
authors.initials: CR
authors.lastname: Padovani
authors.forename: Flavio F
authors.initials: FF
authors.lastname: Aragon
authors.forename: Antonio C
authors.initials: AC
authors.lastname: Cicogna
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism*; D006984:Hypertrophy; D007537:Isometric Contraction / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology*; D051381:Rats; D017208:Rats, Wistar; D012146:Rest / Q000502:physiology; D013599:Systole / Q000187:drug effects
chemical_list: D007545:Isoproterenol; D002118:Calcium