Increased contractile potential of papillary muscles from exercise-trained rat hearts
Female rats (n = 24) swam 6 h/day, 5 days/wk, for over 6 wk. Training increased both wet and dry weight of ventricles 15% above control. The active length-tension curve for trained left ventricular papillary muscles (LVPM) was elevated, with maximum tension (Tmax) at optimal length 37% higher than t...
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Published in | The American journal of physiology Vol. 234; no. 4; p. H421 |
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Main Author | |
Format | Journal Article |
Language | English |
Published |
United States
01.04.1978
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Subjects | |
Online Access | Get more information |
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Summary: | Female rats (n = 24) swam 6 h/day, 5 days/wk, for over 6 wk. Training increased both wet and dry weight of ventricles 15% above control. The active length-tension curve for trained left ventricular papillary muscles (LVPM) was elevated, with maximum tension (Tmax) at optimal length 37% higher than that of untrained LVPM. Training did not alter passive length-tension, time-to-peak tension (TPT), or half-relaxation time (1/2RT). The maximum rate of tension development (dT/dt), however, was increased 22% by training. The force-velocity curve of trained LVPM was shifted upward; both estimated Vmax and the minimum isometric load where shortening equals zero were greater than control. Exogenous isoproterenol (5.8 nM) did not affect Tmax but significantly decreased TPT and 1/2RT to the same extent for both groups of muscles. Maximum dT/dt was increased to a greater extent by isoproterenol for trained LVPM. These findings indicate hearts hypertrophied by exercise have an increased contractile potential per unit of myocardial mass. |
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ISSN: | 0002-9513 |
DOI: | 10.1152/ajpheart.1978.234.4.h421 |