Changes in the plasma membrane associated with endocrine activity
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Membrane events occurring during and after the process of exocytosis have been studied in highly stimulated human parathyroid chief cells. These chief cells were derived from adenomas removed from three patients with the clinical and ultrastructural findings of a very active (pernicious) hyperparathyroidism. Comparison of thin sections with freeze-fracture replicas shows that the release of secretory granules is preceded by a frequent tandem-like arrangement, and a close attachment of the granules to the plasma membrane by an area of increased cytoplasmic density. In freeze-fracture replicas fusion between granule and plasma membrane is marked by a conspicuous clearing of particles, followed by an extrusion of the core. Membrane recycling after this discharge process is suggested by the finding in thin sections of large invaginations and endocytic vesicles with a bristle coating. Freeze-fracture replicas demonstrate that the split membranes of these large infoldings of the plasmalemma are studded by intramembranous particles identical to those of the surrounding plasma membrane. Detachment of the endocytic vesicles is characterized by a small impression devoid of particles, which is indicative of an area of membrane fusion, following collapse of the invaginations. Our results support the view that membrane fusion occurs between protein-depleted, lipid-containing layers and that a relationship exists between exocytosis of secretory granules and subsequent retrieval of residues of the granule membrane.
Key wordsHuman parathyroid cells Plasma membrane Secretory granules Exo-endocytosis Membrane recycling
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- Chandler DE (1979) Quick freezing avoids specimen preparation artifacts in membrane-fusion studies. In: Rash JE, Hudson CS (eds) Freeze fracture: Methods, artifacts, and interpretations. Raven Press, New York, p 81–87Google Scholar
- Hesketh JE, Aunis D, Mandel P, Devilliers G (1978) Biochemical and morphological studies of bovine adrenal medullary myosin. Biol Cell 33:199–208Google Scholar
- Heuser JE, Reese TS (1979) Synaptic-vesicle exocytosis captured by quick-freezing. In: Schmitt FO, Worden FG (eds.) The neurosciences. The MIT Press, Cambridge (Mass) London, p 573–600Google Scholar
- Ravazzola M, Orci L (1977) Intercellular junctions in the rat parathyroid gland: a freeze-fracture study. Biol Cell 28:137–144Google Scholar