Calcium release by cholecystokinin analogue OPE is IP3 dependent in single rat pancreatic acinar cells.
Cholecystokinin (CCK) and carbachol raise intracellular Ca2+ concentration ([Ca2+]i) in pancreatic acinar cells by elevating inositol 1,4,5-trisphosphate (IP3). CCK analogues JMV-180 and OPE stimulate fully efficacious enzyme secretion and [Ca2+]i oscillations but release Ca2+ from intracellular stores by apparently IP3-independent mechanisms in permeabilized acinar cells. In the present study, we investigated whether OPE mobilizes Ca2+ from IP3-sensitive Ca2+ stores and whether IP3 mediates such responses in single intact cells. OPE and JMV-180 similarly elevated IP3 to low levels compared with those elicited by 10 nM CCK. Depletion of IP3-sensitive stores by elevation of intracellular IP3 using carbachol, microinjection of a nonmetabolizable IP3 analogue, or exposure to thapsigargin, in the absence of extracellular Ca2+, depleted the same Ca2+ stores that were sensitive to OPE. In converse experiments, OPE depleted carbachol- or thapsigargin-sensitive stores, indicating that carbachol-, thapsigargin-, IP3-, and OPE-sensitive Ca2+ stores overlap completely and that stores mobilized by OPE are IP3 sensitive. To determine whether IP3 mediates responses to OPE, cells were microinjected with low-molecular-weight heparin, a competitive inhibited the rise of [Ca2+]i in response to carbachol, OPE, or JMV-180, whereas de-N-sulfated heparin, an inactive heparin, was without effect. These results indicate that CCK analogues release Ca2+ from IP3-sensitive Ca2+ stores by mechanisms involving the IP3 receptor.
Gaisano
H Y
HY
Department of Medicine, University of Toronto, Ontario, Canada.
Wong
D
D
Sheu
L
L
Foskett
J K
JK
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002469:Cell Separation; D002766:Cholecystokinin / Q000031:analogs & derivatives* / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000378:metabolism; D008297:Male; D008845:Microinjections; D009994:Osmolar Concentration; D010179:Pancreas / Q000166:cytology / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D012844:Sincalide / Q000031:analogs & derivatives / Q000494:pharmacology
D010446:Peptide Fragments; C067408:cholecystokinin (26-32), Tyr-Gly-Nle(28,31) phenethyl ester-; C058451:JMV 180; D015544:Inositol 1,4,5-Trisphosphate; D002217:Carbachol; D002766:Cholecystokinin; D012844:Sincalide; D002118:Calcium