Journal of Applied Physiology, Vol 64, Issue 3 1179-1185, Copyright © 1988 by American Physiological Society
Coronary vasodilator reserve, capillarity, and mitochondria in trained hypertensive rats
R. J. Tomanek, C. V. Gisolfi, C. A. Bauer and P. J. Palmer
Department of Anatomy, University of Iowa, Iowa City 52242.
To test the hypothesis that exercise training can reverse the decrements in
coronary reserve, capillary density, and mitochondrial volume density
evident during established hypertension, we trained spontaneously
hypertensive (SHR) and normotensive (WKY) rats on a treadmill over a 3-mo
period. At 7 mo of age we used microspheres to evaluate myocardial
perfusion in conscious rats. Exercise training did not alter hypertension
or left ventricular hypertrophy but did increase maximal O2 consumption in
both SHR and WKY. A decrement in left and right ventricular coronary
reserve in SHR, compared with WKY, was indicated by 1) a smaller increment
in myocardial perfusion during maximal vasodilation with dipyridamole and
2) a higher minimal coronary vascular resistance per unit mass. Exercise
training had no significant effect on any index of myocardial perfusion in
SHR or WKY. A 12% decrement in capillary numerical density in the
endomyocardium of SHR was not reversed by exercise training. We estimated
the volume densities of mitochondria, myofibrils, and sarcoplasm using
electron microscopy and point-counting stereology on perfusion-fixed
hearts. None of the parameters in either SHR or WKY was changed by exercise
training. It is concluded that exercise training does not reverse the
decrements in coronary reserve and capillary numerical density associated
with hypertension in adult rats. Moreover the previously observed
enhancement of mitochondrial volume density due to exercise in young
hypertensive rats was not observed in adult SHR.
