title: Morphometry of right ventricular hypertrophy induced by strenuous exercise in rat.
abstract: 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.
mesh_terms: D000818:Animals; D001835:Body Weight; D002196:Capillaries / Q000503:physiopathology; D006332:Cardiomegaly / Q000209:etiology / Q000503:physiopathology*; D003326:Coronary Circulation; D003331:Coronary Vessels / Q000503:physiopathology; D006321:Heart / Q000033:anatomy & histology*; D006325:Heart Atria / Q000033:anatomy & histology; D009929:Organ Size; D005082:Physical Exertion; D051381:Rats; D011919:Rats, Inbred Strains