Low-intensity physical training and detraining: evaluation of morphological and mechanical properties of cardiac myocytes from spontaneously hypertensive rats / Treinamento físico de baixa intensidade e destreinamento: avaliação das propriedades morfológicas e mecânicas de miócitos cardíacos de ratos espontaneamente hipertensos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The aim of this study was to verify whether low-intensity treadmill running training and detraining affect blood pressure, morphological and contractile properties of single left ventricular myocytes in spontaneously hypertensive rats (SHR). Sixteen-week old SHR male rats with initial body weight of 328.8 6.58 g (mean SEM) and blood pressure of 174.1 3.75 mmHg, where randomly allocated into one of the four groups: G1, sedentary 8 weeks (n = 7); G2, exercised 8 weeks (n = 7); G3, detrained 4 weeks (n = 7); G4 = sedentary 12 weeks (n = 6). Animals from G2 and G3 groups were submitted to a low-intensity treadmill running training (16m/min), 60 min/day, 5 days/week, for 8 weeks. Animals from G3 were kept sedentary in their cages for the following 4 weeks. At sacrifice, the heart was removed and left ventricular myocytes were enzymatically dispersed. Cell length and width were measured using an image capture system and cell volume was calculated. Myocytes were stimulated at 1 Hz at room temperature (25C) and cell contractility was measured by using an edge detection system. The results showed that by the end of experimental period no between group differences was observed in body weight, heart weight, ventricular weight and the ratios heart weight:body weight and ventricular weight:body weight. Initial and final blood pressure were not different in all groups. Cell length of G2 rats was higher than that of G1 (P <0.05) and detraining did not affect such adaptation. However, neither exercise training nor detraining affected cell width and volume (P >0.05). The amplitude of contraction was not affected by either exercise training or detraining (P >0.05). The time to peak of contraction was reduced by exercise training (P <0.05), but after detraining such adaptation has disappeared. The time to 50% of relaxation tended to be reduced by the exercise training program (P=0.08), but after detraining such trend disappeared. The maximal velocity of contraction of myocytes from G2 animals was higher than that of G1 (P <0.05) and detraining did not affect such adaptation. The maximal velocity of relaxation was higher in cells from G2 animals, as compared to that of G1 (P <0.05), which was maintained after detraining. In conclusion: a) The low-intensity running training and detraining did not affect SHR blood pressure; b) The running training program increased SHR cardiac length without affecting cell width and volume, but detraining did not affect cell morphology; and c) The training program did not affect SHR cardiac amplitude of contraction, however, it increased the maximal velocity of contraction and relaxation, nevertheless detraining reversed the time to peak of contraction.

ASSUNTO(S)

cardiac myocytes hypertension sedentarism miócitos cardíacos physical activity atividade física hipertensão educacao fisica inatividade

ACESSO AO ARTIGO

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