Intracellular transport of sulfated macromolecules in parotid acinar cells.

Intracellular transport of sulfated macromolecules in parotid acinar cells was investigated by electron microscopic radioautography after injection of 35S-sulfate. Ten minutes after injection radiosulfate was concentrated in the Golgi region. By 1 hr, much of the radioactive material had been transported to condensing vacuoles. These vacuoles were subsequently transformed into zymogen granules which contained almost 70% of the radioactivity 4 hrs after injection. These results indicate that, in addition to its packaging function, the Golgi apparatus in parotid acinar cells is capable of utilizing inorganic sulfate for the production of sulfated macromolecules. These molecules, following an intracellular route similar to that taken by digestive enzymes, become an integral component of zymogen granules. The possibility that sulfated macromolecules play a role in exocrine secretion by aiding in the packaging of exportable proteins is discussed.