title: Effect of exercise training on aging-induced changes in rat papillary muscle.
abstract: BACKGROUND
  The effects of aging on papillary muscle have been widely demonstrated, but no data on the effects of exercise on the age-related changes are available.
  
  
  OBJECTIVE
  To analyze the effects of aging on the morphological and quantitative properties of papillary muscle and investigate whether a long-term moderate exercise program would exert a protective effect against the effects of aging.
  
  
  METHODS
  We used electron microscopy to study the density of myocytes, capillaries and connective tissue and the cross-sectional area of myocytes of the papillary muscle of the left ventricle of 6- and 13-month-old untrained and exercised Wistar rats.
  
  
  RESULTS
  As expected, the volume density of myocytes declined significantly (p<0.05) with aging. The length density of myocardial capillaries also declined with aging, but not significantly. The interstitial volume fraction of the papillary muscle tissue increased significantly (P<0.05) with age. The number of myocyte profiles showed a reduction of 20% that was accompanied by myocyte hypertrophy in the aged rats (P<0.05). Animals submitted to a 60-minute daily session,, 5 days/wk at 1.8 km x h(-1) of moderate running on a treadmill for 28 weeks showed a reversion of all the observed aging effects on papillary muscle.
  
  
  CONCLUSIONS
  The present study supports the concept that long-term exercise training restrains the aging-related deleterious changes in the papillary muscle.
authors.affiliation: Laboratório de Biodinâmica, Universidade São Judas Tadeu, São Paulo, SP, Brasil. lmaifrino@uol.com.br
authors.forename: Laura Beatriz Mesiano
authors.initials: LB
authors.lastname: Maifrino
authors.forename: Rubens Correa
authors.initials: RC
authors.lastname: Araújo
authors.forename: Cristiane Castro
authors.initials: CC
authors.lastname: Faccini
authors.forename: Edson Aparecido
authors.initials: EA
authors.lastname: Liberti
authors.forename: Eliane Florêncio
authors.initials: EF
authors.lastname: Gama
authors.forename: Antonio Augusto Coppi Maciel
authors.initials: AA
authors.lastname: Ribeiro
authors.forename: Romeu Rodrigues de
authors.initials: RR
authors.lastname: Souza
mesh_terms: D000375:Aging / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D006352:Heart Ventricles / Q000648:ultrastructure; D008297:Male; D032383:Myocytes, Cardiac / Q000502:physiology* / Q000648:ultrastructure; D010210:Papillary Muscles / Q000502:physiology* / Q000648:ultrastructure; D010805:Physical Conditioning, Animal / Q000379:methods; D051381:Rats; D017208:Rats, Wistar