Studies on ultrastructure and cytochemical ATPase activity in human cardiac myocytes from biopsies from patients with various heart diseases.

Ultrastructural localization and intensity of ATPase activity were studied in myocardial cells from biopsies with reference to fine-structural alterations and cardiac functions in patients with various heart diseases. ATPase activity was found to be intense in the sarcoplasmic reticulum (SR), the matrices of the mitochondria (Mt), on the myofilaments (Mf) and along the gap-junctions of intercalated discs in the control myocardial cells. ATPase activity was more intense in cardiac myocytes from well-functioning or ultrastructurally well preserved hearts. In failing and degenerating hearts, ATPase activity was decreased. ATPase activity was more intense in clinically-improving than in clinically-worsening patients. However, the localized pattern of ATPase activity was similar in each heart disease. These results suggest that cytochemical observation of ATPase activity can reflect not only fine structural changes in cardiac myocytes, but also the metabolic state in the diseased heart, and is valuable therefore from the standpoint of clinical medicine.