Buds of the Golgi apparatus in parotid acinar cells.

The Golgi apparatus (GA) is a membranous organelle composed of stacked cisterns with associated vesicles. This study was undertaken to determine its origin in rat parotid acinar cells. The morphogenesis of the GA could be recognized in the developmental process as well as in mitotic division of cells. EM studies depicted an aggregation of small vesicles in the early stage of postnatal development or mitosis, that appeared to be the rudimental element of GA. Brefeldin A induced rapid degradation of the cisternal structure to vesicular aggregates. Reconstruction of the GA structure based on these remnant vesicles was observed upon removal of the drug. Similar membranous assembly could be observed after destruction of microtubules. These membranous aggregates presumably corresponded to 'buds of the GA' in parotid acinar cells. However, conventional cytochemical markers for GA were not detected on such immature form of GA. We found that the GA matrix protein GM130 and osmium reductivity (a classical marker for cis-Golgi elements) were consistently localized in the GA elements. Therefore, immunohistochemical distribution of GM130 and osmium impregnation of parotid acinar cells were studied under various dynamic conditions that produced structural modification of the GA.