Calcium immobilization in mitochondria of failing myocardium: X-ray microanalytical evidence

Electron microscopic study of myocardial cells from rat failing heart (chronic congestive heart failure—advanced, near-terminal state—produced by stenosis of the descending aorta) showed that about 80% of mitochondrial profiles contained electron-opaque deposits, which occupied about 5% of the mitochondrial volume. X-ray analytical electron microscopy of mitochondria in situ (line-scanning and spot analyses) indicated that these electron-opaque deposits contained a significant amount of calcium. The mitochondrial electron-opaque deposits represent sites of calcium immobilization in a complex of proteins and lipids, presumably derived from damaged mitochondrial membranes.