Calcium and Pancreatic Secretion. I. Subcellular Distribution of Calcium and Magnesium in the Exocrine Pancreas of the Guinea Pig

The distribution of calcium and magnesium has been studied in the acinar cells of the pancreas of the guinea pig. Most of the magnesium was found to be associated with the rough microsomes (probably bound to the ribosomes) and with the postmicrosomal supernate. In contrast, calcium was distributed a...

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Bibliographic Details
Published in:The Journal of cell biology 1975-04, Vol.65 (1), p.88-102
Main Authors: Clemente, François, Meldolesi, Jacopo
Format: Article
Language:English
Subjects:
Acinar cells
Animals
Calcium
Calcium - analysis
Cell Fractionation
Cell Membrane - analysis
Cell Membrane - ultrastructure
Cell membranes
Chymotrypsinogen - analysis
Electron Transport Complex IV - analysis
Guinea Pigs
Homogenization
Magnesium
Magnesium - analysis
Microscopy, Electron
Mitochondria - analysis
Mitochondria - ultrastructure
Organelles
Pancreas
Pancreas - analysis
Pancreas - enzymology
Pancreas - ultrastructure
Potassium
Secretion
Secretory vesicles
Subcellular Fractions - analysis
Trypsinogen - analysis
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Summary:The distribution of calcium and magnesium has been studied in the acinar cells of the pancreas of the guinea pig. Most of the magnesium was found to be associated with the rough microsomes (probably bound to the ribosomes) and with the postmicrosomal supernate. In contrast, calcium was distributed among all the particulate fractions, primarily the mitochondria, microsomes (especially smooth surfaced), zymogen granules, and the plasmalemma, and was low in the postmicrosomal supernate. Most of the calcium recovered in the particulate fractions was found to be membrane bound. The highest concentrations were found in the membranes of the zymogen granules and in the plasmalemma. By means of control experiments using 45Ca as the tracer, it was established that a considerable redistribution of calcium occurs during homogenization and cell fractionation. At least some of the resulting artifacts were estimated quantitatively and the data were corrected accordingly. The biochemical results were confirmed with the cytochemical antimonate technique carried out on the tissue as well as on isolated fractions. The role of calcium associated with the zymogen granules and with their limiting membranes is discussed in relation to the architecture of the granule and to the functionality of the pancreatic juice.
ISSN:0021-9525
1540-8140
DOI:10.1083/jcb.65.1.88