title: Morphology and contractility in cardiomyocytes of rats with low exercise performance.
abstract: BACKGROUND
  Aerobic capacity is essential to physical performance, and low aerobic capacity is related to the triggering of various cardiovascular diseases.
  
  
  OBJECTIVE
  To compare the morphology and contractility of isolated rat cardiomyocytes with low performance and standard performance for exercise.
  
  
  METHODS
  Wistar rats with 10 weeks of age underwent a protocol of treadmill running to fatigue, and were divided into two groups: Low Performance (LP) and Standard Performance (SP). Then, the animals were sacrificed, the heart was quickly removed and, by means of enzymatic dissociation, left ventricular cardiomyocytes were isolated. The cell and sarcomeres length and width of cardiomyocytes were measured using an edge detection system. The isolated cardiomyocytes were electrically stimulated at 1 and 3 Hz and cell contraction was measured by registering the change of their length.
  
  
  RESULTS
  The cell length was shorter in the LP group (157.2 ± 1.3 µm; p < 0.05) compared to SP (161.4 ± 1.3 µm), and the same result was observed for the volume of cardiomyocytes (LP, 25.5 ± 0.4 vs. SP, 26.8 ± 0.4 pL; p < 0.05). The time to peak contraction (LP, 116 ± 1 vs. SP 111 ± 2 ms) and total relaxation (LP, 143 ± 3 vs. SP 232 ± 3 ms) were higher in the LP group.
  
  
  CONCLUSIONS
  We conclude that left ventricular myocytes of animals with low performance for exercise are smaller than animals with standard performance. In addition to that, they present losses in contractile capacity.
authors.affiliation: Universidade Federal de Viçosa, Viçosa, MG, Brazil.
authors.forename: Judson Fonseca
authors.initials: JF
authors.lastname: Quintão-Júnior
authors.forename: Antônio José
authors.initials: AJ
authors.lastname: Natali
authors.forename: Miguel Araújo
authors.initials: MA
authors.lastname: Carneiro-Júnior
authors.forename: Cynthia Aparecida de
authors.initials: CA
authors.lastname: Castro
authors.forename: Lucas Rios
authors.initials: LR
authors.lastname: Drummond
authors.forename: Victor Neiva
authors.initials: VN
authors.lastname: Lavorato
authors.forename: Leonardo Bonato
authors.initials: LB
authors.lastname: Felix
authors.forename: Jader dos Santos
authors.initials: Jdos S
authors.lastname: Cruz
authors.forename: Thales Nicolau
authors.initials: TN
authors.lastname: Prímola-Gomes
mesh_terms: D000818:Animals; D015992:Body Mass Index; D048429:Cell Size; D005080:Exercise Test; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000166:cytology*; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000502:physiology*; D009929:Organ Size; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D016277:Ventricular Function, Left / Q000502:physiology