Calcium dependence of proteinase-activated receptor 2 and cholecystokinin-mediated amylase secretion from pancreatic acini.
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.
Sharma
Anupriya
A
Dept. of Surgery, Tufts-New England Medical Center, Boston, MA 02111, USA.
Tao
Xiaohong
X
Gopal
Arun
A
Ligon
Brooke
B
Steer
Michael L
ML
Perides
George
G
D000681:Amylases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002108:Ceruletide / Q000494:pharmacology; D002766:Cholecystokinin / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009842:Oligopeptides / Q000494:pharmacology; D010179:Pancreas / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D044464:Receptor, PAR-2 / Q000502:physiology*; D011949:Receptors, Cholecystokinin / Q000187:drug effects; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors
D004791:Enzyme Inhibitors; D004963:Estrenes; D009842:Oligopeptides; D010726:Phosphodiesterase Inhibitors; D011760:Pyrrolidinones; D044464:Receptor, PAR-2; D011949:Receptors, Cholecystokinin; C112356:seryl-leucyl-isoleucyl-glycyl--arginyl-leucinamide; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D002108:Ceruletide; D002766:Cholecystokinin; D010738:Type C Phospholipases; D000681:Amylases; D002118:Calcium