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Abstract

The ultrastructure and cytochemistry of the Golgi apparatus was studied in acinar cells of the parotid and von Ebner's glands of the rat. The Golgi apparatus was composed of four to six stacked cisternae, numerous small vesicles, and condensing vacuoles. The latter appeared to form as dilatations of the innermost Golgi cisterna, and their irregular membrane suggested fusion with or fission of small vesicles. Nucleoside diphosphatase and thiamine pyrophosphatase activities were localized to the inner Golgi cisternae. Acid phosphatase activity was localized to condensing vacuoles, coated vesicles, and an irregular, narrow cisterna found in the internal region of the Golgi apparatus and termed the internal Golgi lamella. The morphology and relationships of the Golgi apparatus indicate that it plays an important role in secretory granule formation. The presence of nucleoside diphosphatase activity may reflect the role of the Golgi apparatus in the addition of carbohydrates to the secretory proteins. It is suggested that the internal Golgi lamella develops from the inner Golgi cisterna after secretory granule formation is completed. Acid phosphatase activity in condensing vacuoles may be a mechanism for lysosomal regulation of the secretory process.