AJP - Heart and Circulatory Physiology, Vol 248, Issue 1 8-14, Copyright © 1985 by American Physiological Society
Exercise training modifies myocardial mitochondria and myofibril growth in spontaneously hypertensive rats
R. P. Crisman and R. J. Tomanek
We tested the hypothesis that exercise training provides a stimulus that
could modify the decrement in mitochondria-to-myofibril volume ratio
characteristic of myocardial cells hypertrophied in response to a pressure
overload. Spontaneously hypertensive rats (SHR) were trained 5 days/wk on a
treadmill at 70-90% maximal VO2 between the ages of 6 and 16 wk
corresponding to the development of hypertension and cardiac hypertrophy.
The training program increased maximal VO2 and effected a resting
bradycardia but did not alter blood pressure, left ventricular hypertrophy,
or peak cardiac output. Our stereological data from electron micrographs
shows that the decrement in mitochondrial volume density and the increase
in myofibril volume density characteristic of SHR compared with their
normotensive controls (WKY, Wistar-Kyoto rats) were reversed. Thus the
relative volumes of mitochondria and myofibrils and their ratio in trained
SHR were similar to those of the WKY group. The similarity was noted in
myocytes from both the subepicardium and subendocardium. These data suggest
that exercise training facilitates a proportional growth of
energy-producing and energy-consuming organelles in SHR and that this
effect is not secondary to modification of blood pressure or left
ventricular mass.
