ANALYTICAL ELECTRON MICROSCOPY OF ADRENAL CHROMAFFIN CELLS

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The elemental composition in various compartments of the bovine adrenal chromaffin cell was investigated by a combination of energy-dispersive x-ray spectroscopy and electron energy loss spectroscopy. Cryosections of quick-frozen cultured cells were transferred at low temperature (-170 C) into the Hitachi H700H analytical electron microscope and the samples were carefully dehydrated in situ. Spectra were recorded from: (1) secretory granules, (2) cytoplasm, (3) nuclei (4) mitochondria and (5) extracellular space. X-ray spectra were quantitated by means of specially prepared standards containing known amounts of protein and ions. Concentrations accurate to plus/minus 5% or 10% could be established for most of the major elements. Electron energy loss spectra were analyzed with software developed in BEIB to determine ratios of nitrogen-to-phosphorus. Experiments have been performed to investigate the effect of pH on catecholamine secretion and how this is correlated with changes in ionic distributions in the cell. Measurements have also been made on isolated secretory granules.