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Granule swelling in stimulated bovine adrenal chromaffin cells: regulation by internal granule pH.
- Source :
-
Cell and tissue research [Cell Tissue Res] 1995 Jan; Vol. 279 (1), pp. 85-92. - Publication Year :
- 1995
-
Abstract
- Adrenal medullary chromaffin cells secrete catecholamines through exocytosis of their intracellular chromaffin granules. Osmotic granule swelling has been implicated to play a role in the generation of membrane stress associated with the fusion of the granule membrane. However, controversy exists as to whether swelling occurs before or after the actual fusion event. Using morphometric methods we have determined the granule diameter distributions in rapidly frozen, freeze-substituted chromaffin cells. Our measurements show that intracellular chromaffin granules increase in size from an average of 234 nm to 274 nm or 277 nm in cells stimulated to secrete with nicotine or high external K+, respectively. Granule swelling occurs before the formation of membrane contact. Ammonium chloride, an agent which inhibits stimulated catecholamine secretion by approximately 50% by altering the intragranular pH, also inhibits granule swelling. In addition, ammonium chloride-treated secreting cells show more granule-plasma membrane contacts than untreated secreting cells. Sodium propionate induces granule swelling in the absence of secretagogue and has been shown to enhance nicotine- and high K(+)- induced catecholamine release. These results indicate that in adrenal chromaffin cells granule swelling is an essential step in exocytosis before fusion pore formation, and is related to the pH of the granule environment.
- Subjects :
- Adrenal Medulla metabolism
Ammonium Chloride pharmacology
Animals
Catecholamines metabolism
Cattle
Cytoplasmic Granules chemistry
Cytoplasmic Granules drug effects
Freeze Substitution
Membrane Fusion
Nicotine pharmacology
Potassium pharmacology
Propionates pharmacology
Adrenal Medulla ultrastructure
Cytoplasmic Granules physiology
Exocytosis drug effects
Hydrogen-Ion Concentration
Subjects
Details
- Language :
- English
- ISSN :
- 0302-766X
- Volume :
- 279
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Cell and tissue research
- Publication Type :
- Academic Journal
- Accession number :
- 7895265
- Full Text :
- https://doi.org/10.1007/BF00300694