Uraemic myocardial disease. An experimental study, with special reference to the effect of parathyroidectomy.

A histopathological study of the myocardium was performed in rats made uraemic by a 5/6 kidney resection. The examinations were performed after intervals up to 36 weeks. Uraemia caused focal myocardial necroses, the incidence and severity of which were related to the length and severity of the uraemic state. In the myocardium of some animals intracellularly located calcifications were found. The calcifications usually appeared only in the necrotic areas. The coronary arteries showed only slight or moderate arteriosclerosis without severe obturation of the lumens and the genesis of the necroses is suggested to be factors other than ischaemia or hypoxia. Since secondary hyperparathyroidism might be one such factor, the effect of prior parathyroidectomy was studied. Parathyroidectomy prevented the development of calcifications but not the development of necrosis. However, the significance of secondary hyperparathyroidism in the development of myocardial necroses cannot be fully evaluated from the present study. The protecting effect of parathyroidectomy was probably counterbalanced by the deleterious effect of further elevated serum phosphate levels in the parathyroidectomized animals.