Journal
BRAZILIAN JOURNAL OF MEDICAL AND BIOLOGICAL RESEARCH
Volume 43, Issue 11, Pages 1042-1046Publisher
ASSOC BRAS DIVULG CIENTIFICA
DOI: 10.1590/S0100-879X2010007500117
Keywords
Physical activity; Inactivity; Hypertension; Cardiomyocytes
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Funding
- FAPEMIG [CDS 2286-5.01/07]
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We determined the effects of exercise training and detraining on the morphological and mechanical properties of left ventricular myocytes in 4-month-old spontaneously hypertensive rats (SHR) randomly divided into the following groups: sedentary for 8 weeks (SED-8), sedentary for 12 weeks (SED-12), treadmill-running trained for 8 weeks (TRA, 16 m/min, 60 min/day, 5 days/week), and treadmill-running trained for 8 weeks followed by 4 weeks of detraining (DET). At sacrifice, left ventricular myocytes were isolated enzymatically, and resting cell length, width, and cell shortening after stimulation at a frequency of 1 Hz (similar to 25 degrees C) were measured. Cell length was greater in TRA than in SED-8 (161.30 +/- 1.01 vs 156.10 +/- 1.02 mu m, P < 0.05, 667 vs 618 cells, respectively) and remained larger after detraining. Cell width and volume were unaffected by either exercise training or detraining. Cell length to width ratio was higher in TRA than in SED-8 (8.50 +/- 0.08 vs 8.22 +/- 0.10, P < 0.05) and was maintained after detraining. Exercise training did not affect cell shortening, which was unchanged with detraining. TRA cells exhibited higher maximum velocity of shortening than SED-8 (102.01 +/- 4.50 vs 82.01 +/- 5.30 mu m/s, P < 0.05, 70 cells per group), with almost complete regression after detraining. The maximum velocity of relengthening was higher in TRA cells than in SED-8 (88.20 +/- 4.01 vs 70.01 +/- 4.80 mu m/s, P < 0.05), returning to sedentary values with detraining. Therefore, exercise training affected left ventricle remodeling in SHR towards eccentric hypertrophy, which remained after detraining. It also improved single left ventricular myocyte contractile function, which was reversed by detraining.
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