Intracellular localization of calcium in the chromaffin cells of the rat adrenal medulla.

The ulstrastructural localization of calcium in the chromaffin cells of the adrenal medulla was carried out by using potassium pyroantimonate during fixation. Calcium-containing deposits were either diffuse within the cytoplasm or associated with membrane-bounded organelles. Variable amounts of precipitates were found within the nucleus and in the Golgi complex. However, the major sites of calcium antimonate deposits were the secretory granules and the mitochondria. The morphological identification of calcium-storing organelles in the adreno-medullary cells may be useful in evaluating the involvement of such intracellular compartments during the secretory process.