Determination of hydroxyproline content in human heart muscle

Hydroxyproline content was chemically determined on 45 human hearts obtained at autopsy in order to study whether hydroxyproline contents vary in proportion to heart weight or not. There were no significant differences in the mean hydroxyproline content between the epicardium and the endocardium, between the left ventricle and the right ventricle, or among cardiovascular and renal disease group, malignant disease group and miscellaneous disease group. Total hydroxyproline content per mg dry weight of the left ventricle increased proportionally with heart weight. Hydroxyproline content in neutral salt soluble fraction increased more proportionally than that in acid soluble fraction. This tendency was more evident in the endocardium than in the epicardium of the left ventricle. These results seem to be well consistent with those of histometrical estimation of scar tissue in human heart muscle. Hydroxyproline content in acid soluble fraction of the right ventricle was increased proportionally with heart weight.