[Myocardial hypertrophy during experimental hypertension in young and old animals]

The myocardium of young rabbits aged 6-10 months and old rabbits aged 3.5-4.5 years and that of rabbits of the same age with experimental hypertension (the renal pattern) was studied by the morphometry and gravimetry techniques and electron microscopy. The myocardial mass and the number of hypertrophied fibers 16.5-22.1 microns in diameter were discovered to increase in old animals with advancing age. Young rabbits with hypertension of a 4-month standing manifested an increment in the myocardial mass and in the number of hypertrophied muscle fibers. The pattern of the distribution of cardiomyocytes as per diameter and connective tissue content of the heart in such rabbits was similar to that seen in the old heart. Old animals with hypertension showed an insignificant rise of the myocardial mass at the same times and a statistically significant lowering in the number of hypertrophied fibers in contradistinction to young hypertensive rabbits. At the same time the myocardium exhibited an increase in the number of dystrophic and necrotic cells and enlargement of the foci on substitutive sclerosis.