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Calcium dependence of proteinase-activated receptor 2 and cholecystokinin- mediated amylase secretion from pancreatic acini

Calcium dependence of proteinase-activated receptor 2 and cholecystokinin- mediated amylase... Pancreatic acini secrete digestive enzymes in response to a variety of secretagogues including CCK and agonists acting via proteinase-activated receptor-2 (PAR2). We employed the CCK analog caerulein and the PAR2-activating peptide SLIGRL-NH 2 to compare and contrast Ca 2+ changes and amylase secretion triggered by CCK receptor and PAR2 stimulation. We found that secretion stimulated by both agonists is dependent on a rise in cytoplasmic Ca 2+ concentration (Ca 2+ i ) and that this rise in Ca 2+ i reflects both the release of Ca 2+ from intracellular stores and accelerated Ca 2+ influx. Both agonists, at low concentrations, elicit oscillatory Ca 2+ i changes, and both trigger a peak plateau Ca 2+ i change at high concentrations. Although the two agonists elicit similar rates of amylase secretion, the rise in Ca 2+ i elicited by caerulein is greater than that elicited by SLIGRL-NH 2 . In Ca 2+ -free medium, the rise in Ca 2+ i elicited by SLIGRL-NH 2 is prevented by the prior addition of a supramaximally stimulating concentration of caerulein, but the reverse is not true; the rise elicited by caerulein is neither prevented nor reduced by prior addition of SLIGRL-NH 2 . Both the oscillatory and the peak plateau Ca 2+ i changes that follow PAR2 stimulation are prevented by the phospholipase C (PLC) inhibitor U73122 , but U73122 prevents only the oscillatory Ca 2+ i changes triggered by caerulein. We conclude that 1 ) both PAR2 and CCK stimulation trigger amylase secretion that is dependent on a rise in Ca 2+ i and that Ca 2+ i rise reflects release of calcium from intracellular stores as well as accelerated influx of extracellular calcium; 2 ) PLC mediates both the oscillatory and the peak plateau rise in Ca 2+ i elicited by PAR2 but only the oscillatory rise in Ca 2+ i elicited by CCK stimulation; and 3 ) the rate of amylase secretion elicited by agonists acting via different types of receptors may not correlate with the magnitude of the Ca 2+ i rise triggered by those different types of secretagogue. caerulein; phospholipase C Address for reprint requests and other correspondence: G. Perides, Tupper 205, Dept. of Surgery #37, Tufts-New England Medical Center, 750 Washington St., Boston, MA 02111 (e-mail: gperides@tufts-nemc.org ) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png AJP - Gastrointestinal and Liver Physiology The American Physiological Society

Calcium dependence of proteinase-activated receptor 2 and cholecystokinin- mediated amylase secretion from pancreatic acini

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Publisher
The American Physiological Society
Copyright
Copyright © 2011 the American Physiological Society
ISSN
0193-1857
eISSN
1522-1547
DOI
10.1152/ajpgi.00342.2004
pmid
15976386
Publisher site
See Article on Publisher Site

Abstract

Pancreatic acini secrete digestive enzymes in response to a variety of secretagogues including CCK and agonists acting via proteinase-activated receptor-2 (PAR2). We employed the CCK analog caerulein and the PAR2-activating peptide SLIGRL-NH 2 to compare and contrast Ca 2+ changes and amylase secretion triggered by CCK receptor and PAR2 stimulation. We found that secretion stimulated by both agonists is dependent on a rise in cytoplasmic Ca 2+ concentration (Ca 2+ i ) and that this rise in Ca 2+ i reflects both the release of Ca 2+ from intracellular stores and accelerated Ca 2+ influx. Both agonists, at low concentrations, elicit oscillatory Ca 2+ i changes, and both trigger a peak plateau Ca 2+ i change at high concentrations. Although the two agonists elicit similar rates of amylase secretion, the rise in Ca 2+ i elicited by caerulein is greater than that elicited by SLIGRL-NH 2 . In Ca 2+ -free medium, the rise in Ca 2+ i elicited by SLIGRL-NH 2 is prevented by the prior addition of a supramaximally stimulating concentration of caerulein, but the reverse is not true; the rise elicited by caerulein is neither prevented nor reduced by prior addition of SLIGRL-NH 2 . Both the oscillatory and the peak plateau Ca 2+ i changes that follow PAR2 stimulation are prevented by the phospholipase C (PLC) inhibitor U73122 , but U73122 prevents only the oscillatory Ca 2+ i changes triggered by caerulein. We conclude that 1 ) both PAR2 and CCK stimulation trigger amylase secretion that is dependent on a rise in Ca 2+ i and that Ca 2+ i rise reflects release of calcium from intracellular stores as well as accelerated influx of extracellular calcium; 2 ) PLC mediates both the oscillatory and the peak plateau rise in Ca 2+ i elicited by PAR2 but only the oscillatory rise in Ca 2+ i elicited by CCK stimulation; and 3 ) the rate of amylase secretion elicited by agonists acting via different types of receptors may not correlate with the magnitude of the Ca 2+ i rise triggered by those different types of secretagogue. caerulein; phospholipase C Address for reprint requests and other correspondence: G. Perides, Tupper 205, Dept. of Surgery #37, Tufts-New England Medical Center, 750 Washington St., Boston, MA 02111 (e-mail: gperides@tufts-nemc.org )

Journal

AJP - Gastrointestinal and Liver Physiology – The American Physiological Society

Published: Oct 1, 2005

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