X-ray microanalysis of mitochondrial deposits in ischemic myocardium

The x-ray microanalysis technique was used to determine the chemical composition of intramitochondrial electron-dense deposits in ischemic myocardial cells. Semi-thin sections were cut from Araldite-embedded tissue and analyzed in a scanning electron microscope equipped with energy- and wavelength-dispersive spectrometers. The energy dispersive spectrum revealed calcium and phosphorus peaks over many mitochondrial deposits. Peak to background ratios of calcium, phosphorus and magnesium obtained with the wavelength dispersive spectrometer were 1.7, 8.8 and 1.2, respectively. There was no consistent relationship in the characteristic peaks of calcium and phosphorus in a given mitochondrial granule. Magnesium appears to be negligible, except in some mitochondrial deposits which lacked calcium, where it was present with a peak to background ratio of two. These results suggest formation of calcium or magnesium phosphate in the mitochondria during ischemia. X-ray microanalysis can provide detailed information on subcellular electrolyte distribution in normal and ischemic myocardial cells and should be attempted with improved methods of tissue preparation.