Exocytosis couples to endocytosis of ferritin in parotid acinar cells from isoprenalin stimulated rats.

Distribution of acid phosphatase as a marker enzyme for lysosomes was investigated in the isoprenalin stimulated rat parotid gland. The enzyme was localized in lipofuscin-like bodies as well as in non-discharged granules. The appearance of these bodies was correlated in time to the appearance of smooth vesicles and reduction of the acinar lumen. Ferritin, used as a tracer and introduced into the stimulated gland via cannulated parotid ducts, was found in smooth vesicles, vacuoles and lipofuscin-like bodies throughout the cytoplasm of the acinar cells. Very often ferritin-containing vesicles were found in the vicinity of the Golgi complex. In most cases the vesicles containing ferritin also showed acid phosphatase reaction product. A possible correlation between the lysosomal system and the process of recycling and degradation of membranes in the stimulated gland is discussed.