title: [Effects of aging on mechanical performance of Wistar rat papillary muscles].
abstract: OBJECTIVE
  To evaluate the effects of age on mechanical performance of rat myocardium.
  
  
  METHODS
  Left ventricular papillary muscles were isolated from male Wistar rats at 1, 3, 6 and 12 months of age. Muscles were studied isometrically and isotonically, stimulated at 0.2 Hz, perfused with Krebs-Henseleit solution having an external calcium concentration of 2.52 mM, and maintained at 28 degrees C.
  
  
  RESULTS
  Peak isometric developed tension was significantly higher in 1 month than 3, 6 and 12 months. Peak rate of isometric tension rise decreased substantially between 1, 3 and 12 months. Time to peak isometric developed tension showed a significant increase of both 3 and 12 months of age. Time to half relaxation increased significantly from 3 to 6 and from 3 to 12 months. Maximum rate of tension decline decreased from 3 to 6 and from 3 to 12 months. No difference in resting tension was noted among any group. Isotonically, peak shortening and time to peak shortening increased from 1 to 3 months of age. Time to half re-lengthening increased from 3 to 6 and from 3 to 12 months of age. No difference in peak shortening velocity, peak relaxation velocity and relative change in muscle length was noted among any groups.
  
  
  CONCLUSIONS
  The maturation affects the mechanical performance of cardiac muscle.
authors.affiliation: Faculdade de Medicina, UNESP, São Paulo.
authors.forename: A C
authors.initials: AC
authors.lastname: Cicogna
authors.forename: C R
authors.initials: CR
authors.lastname: Padovani
authors.forename: S C
authors.initials: SC
authors.lastname: Nardi
authors.forename: M P
authors.initials: MP
authors.lastname: Okoshi
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D007537:Isometric Contraction / Q000502:physiology; D007551:Isotonic Contraction / Q000502:physiology; D008297:Male; D010210:Papillary Muscles / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
vernacular_title: Efeito do envelhecimento sobre o comportamento mecânico dos músculos papilares de ratos Wistar.