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The adrenalin-producing cells of the rat adrenal medulla have been studied by light and electron microscopy. Frozen sections of glutaraldehyde-perfused material were incubated for demonstration of "marker" enzymes for lysosomes (acid phosphatase, aryl sulfatase) and Golgi apparatus (thiamine pyrophosphatase). In addition, the uptake and fate of intravenously administered horseradish peroxidase was followed. Acid phosphatase activity is demonstrable in secretory granules, Golgi saccules, vesicles in the Golgi area and in the agranular tubules and cisternae (GERL) from which secretory granules appear to form at the inner surface of the Golgi apparatus. Endoplasmic reticulum with ribosomes on only one surface is closely apposed to both inner and outer aspects of the Golgi apparatus. Peroxidase is taken up in vesicles, tubules and "cup-like" bodies. The latter apparently transform into multivesicular bodies. A possible source of the acid phosphatase found in multivesicular bodies is the small vesicles from the Golgi apparatus or GERL.
Holtzman et al. (Wed,) studied this question.