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Changes in microfilament distribution during amylase exocytosis in rat parotid salivary glands in vitro
K Okumura1, Y Tojyo, M Kanazawa
1Department of Oral Surgery (1st division) School of Dentistry, Higashi-Nippon-Gakuen University, Hokkaido, Japan.
Abstract:
In parotid acini, microfilaments were predominantly localized at the luminal border when visualized with the fluorescent probe, rhodamine-phalloidin. There was no fluorescence in the cytoplasm. When acini were stimulated by isoprenaline, the membranes of the secretory granules appeared to become undercoated by microfilaments immediately after fusion with the luminal membrane. The intensity of fluorescence was correlated with the extent of enlargement of the lumina. These findings indicate that the microfilament system (actin-myosin contractile system) may play a role in regulating the movement of the luminal plasma membrane rather than in the control of transport and access of secretory granules to the lumen.
Insights
Microfilaments in parotid glands are located at the luminal border. They may regulate plasma membrane movement, not granule transport, after isoprenaline stimulation.
Area of Science:
- Cell Biology
- Histology
- Biochemistry
Background:
- Parotid acini secrete saliva via exocytosis.
- The role of microfilaments in exocytosis is not fully understood.
Purpose of the Study:
- To investigate the localization and function of microfilaments in parotid acini during secretion.
Main Methods:
- Visualization of microfilaments using rhodamine-phalloidin fluorescence.
- Stimulation of parotid acini with isoprenaline.
Main Results:
- Microfilaments were concentrated at the luminal border of parotid acini.
- Following isoprenaline stimulation and granule fusion, microfilaments undercoated the luminal membrane.
- Increased fluorescence intensity correlated with lumen enlargement.
Conclusions:
- The microfilament system, likely actin-myosin, is involved in regulating luminal plasma membrane dynamics.
- Microfilaments do not appear to control secretory granule transport or access to the lumen.