AJP - Heart and Circulatory Physiology, Vol 243, Issue 6 856-H861, Copyright © 1982 by American Physiological Society
Morphometry of right ventricular hypertrophy induced by strenuous exercise in rat
P. Anversa, C. Beghi, V. Levicky, S. L. McDonald and Y. Kikkawa
Effects on the myocardium, particularly those structural properties of the
capillary network relevant to tissue oxygenation, were studied
morphometrically in rats subjected to a severe running program. Physical
conditioning produced a 31% increase in right ventricular weight and only a
12% increase in the weight of the left ventricle. Quantitative analysis of
right ventricular myocardium demonstrated relative decreases in capillary
luminal volume density (-27%) and capillary luminal surface density (-20%)
and an increase in the average maximum distance from the capillary wall to
the mitochondria of myocytes (14%). In contrast, the contractile mass
expanded in proportion to the growth of the ventricle through augmentation
of the cross-sectional area (17%) and length (19%) of the average myocyte.
Evaluation of the subcellular constituents of myocytes showed no change in
the mitochondria-to-myofibril volume ratio. In conclusion, the capillary
bed controlling oxygen availability, diffusion, and transport suggests that
excessive physical activity may be detrimental to the myocardium.
