Treadmill running training induced a shift from V1 to V3 myosin in younger rats (6 or 12 months old) but did not induce a cardiac myosin isozyme transition in older rats (20 or 27 months old).
Does treadmill running alter cardiac myosin isozyme composition across different age groups in female Fischer 344 rats?
Running training induces a shift in cardiac myosin isozymes in younger but not older rats, suggesting age-related alterations in cardiac muscle response to exercise.
We examined the effect of running training on age-related changes in cardiac myosin isozyme composition in rats. Female Fischer 344 rats (6, 12, 20, and 27 months old) were divided into two groups: sedentary control and trained. The trained group rats were trained by treadmill running for up to 60 minutes per day, 5 days per week for 8 weeks at up to 30 m per minute. In sedentary control rats, the proportion of V1 myosin, that is, alpha-myosin heavy chain (MyHC) isoform, decreased progressively from 6 to 27 months of age. In the younger age groups (6 or 12 months old), there was a shift from V1 myosin to V3 myosin (beta-MyHC isoform) in trained hearts. However, the training program did not induce a cardiac myosin isozyme transition in older rats (20 or 27 months old). These results suggest that the mechanisms mediating the responses of cardiac muscle to running training alter during aging.
Machida et al. (2002) studied this question. Treadmill running training vs. Sedentary control was evaluated on Cardiac myosin isozyme composition (proportion of V1 myosin). Treadmill running training induced a shift from V1 to V3 myosin in younger rats (6 or 12 months old) but did not induce a cardiac myosin isozyme transition in older rats (20 or 27 months old).