Secretory vesicles from pancreatic acinar cells have recently been shown to release Ca2+ after stimulation with Ins(1,4,5)P3 [Gerasimenko, Gerasimenko, Belan and Petersen, (1996) Cell 84, 473-480]. These observations have been used in support of the hypothesis that Ca2+ release from secretory vesicles could be an important component of stimulus secretion coupling in exocrine acinar cells. In the rat, ligation of the parotid duct causes a reversible atrophy of the parotid gland. Most notably, after atrophy the acinar cells are reduced in size and no longer contain secretory vesicles [Liu, Smith, and Scott (1996) J. Dent. Res. 74, 900]. We have measured cytosolic free-Ca2+ concentration ([Ca2+]i) in single, acutely isolated, rat parotid acinar cells, and compared Ca2+ mobilization in response to acetylcholine (ACh) stimulation in cells obtained from control animals to that in cells lacking secretory vesicles obtained after atrophy of the parotid gland. Application of 50-5000 nM ACh to control cells gave rise to a typical, dose-dependent, biphasic increase in [Ca2+]i, of which the later, plateau, phase was acutely dependent on the extracellular Ca2+ concentration. An identical pattern of response was observed with cells obtained from atrophic glands. Low concentrations of ACh (10-100 nM) occasionally produced [Ca2+]i oscillations of a similar pattern in cells from both control and atrophic glands. We were able to show that Ca2+ rises first in the apical pole of the cell and the increase then spreads to the rest of the cell in cells from control glands but not in cells from atrophic glands. However, at present we are unable to determine whether this is due to the lack of secretory vesicles or whether the separation is too small to measure in the smaller acinar cells obtained from atrophic glands. We conclude therefore, that secretory vesicles make no significant contribution to overall Ca2+ mobilization in rat parotid acinar cells, nor are they required for oscillatory changes in [Ca2+]i to occur. However we are unable to eliminate completely any role for secretory vesicles in initiating Ca2+ mobilization at the apical pole of the cell.
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Research Article|
March 01 1998
Intracellular calcium signalling in rat parotid acinar cells that lack secretory vesicles Available to Purchase
Peixin LIU;
Peixin LIU
1
1Oral Biology Unit, Department of Clinical Dental Sciences, The University of Liverpool, Liverpool L69 3BX, U.K.
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John SCOTT;
John SCOTT
1Oral Biology Unit, Department of Clinical Dental Sciences, The University of Liverpool, Liverpool L69 3BX, U.K.
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Peter Matthew SMITH
Peter Matthew SMITH
2
1Oral Biology Unit, Department of Clinical Dental Sciences, The University of Liverpool, Liverpool L69 3BX, U.K.
2To whom correspondence should be addressed.
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Publisher: Portland Press Ltd
Received:
August 29 1997
Revision Received:
November 12 1997
Accepted:
November 14 1997
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1998
1998
Biochem J (1998) 330 (2): 847–852.
Article history
Received:
August 29 1997
Revision Received:
November 12 1997
Accepted:
November 14 1997
Citation
Peixin LIU, John SCOTT, Peter Matthew SMITH; Intracellular calcium signalling in rat parotid acinar cells that lack secretory vesicles. Biochem J 1 March 1998; 330 (2): 847–852. doi: https://doi.org/10.1042/bj3300847
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