Collagen content in different areas of normal and hypertrophied rat myocardium.

Hydroxyproline concentration, representing the collagen content, in different areas of hypertrophied hearts from spontaneously hypertensive rats aged 109 and 16 months and in similar areas of hearts from control rats of the same age was investigated. As was expected, the hydroxyproline concentration in the left ventricular free wall from normal rats was lower than in the right ventricle and septum. In different parts of the normal left ventricle (endomyocardial and epimyocardial areas, papillary muscles) the hydroxyproline concentration was approximately the same. In all myocardial parts from the 16-month-old normal rats, the hydroxyproline concentration was greater than in respective tissue from younger (10-month-old) rats. The hydroxyproline concentration was increased in all parts of the hypertrophied myocardium in spontaneously hypertensive rats. The increase was greatest in endomyocardial areas of the left ventricular wall. The difference in increase of hydroxyproline concentration between epimyocardial and endomyocardial areas was greater in 10, than in 16-month-old spontaneously hypertensive rats. In the hypertrophied left ventricular papillary muscles the hydroxyproline concentration was lower than the average hydroxyproline concentration in the hypertrophied left ventricle as a whole. The results of this study demonstrate that pathophysiological changes in the hypertrophied left myocardium of spontaneously hypertensive rats are not the same in all ventricular areas.