Stimulation of pancreatic amylase release is associated with a parallel sustained increase of cytoplasmic calcium.
The kinetics of the changes in the cytoplasmic Ca2+ concentration (Ca2+i) and amylase release were measured in fura-2-loaded pancreatic acinar cells and perifused pancreatic acini, respectively. Cholecystokinin octapeptide (CCK-8) and its amphibian analogue caerulein induced similar dose-related increases of Ca2+i and amylase secretion with threshold concentrations of 2-6 x 10(-12) M, and maximal effects at 2 x 10(-10) M. The action of CCK/caerulein on Ca2+i was complex and similar to that of carbachol and bombesin with a prompt several-fold increase within seconds followed by a gradual decline over more than 5 min to a new sustained suprabasal level. The kinetics of amylase release in response to CCK and carbachol correlated with the changes in Ca2+i. Additions of the antagonists N2,O2-dibutyrylguanosine 3':5'-cyclic monophosphate and atropine after 30 min of CCK-8 and carbachol stimulation, respectively, were associated with prompt lowerings of Ca2+i and inhibitions of amylase secretion. The patterns observed with substance P (SP) and eledoisin were different with high concentrations (10(-8)-10(-7) M) giving monophasic increases of Ca2+i and amylase release. An initial stimulation of cells with a high dose of CCK eliminated the Ca2+i response to further stimulation with CCK, carbachol, bombesin and SP, whereas cells subjected to initial stimulation with SP responded to subsequent exposure to CCK with prolonged elevation of Ca2+i. The data indicate that stimulation with CCK, carbachol and bombesin may be associated with intracellular mobilization of calcium from more than one pool, and that an increase of Ca2+i is involved even in threshold stimulation of amylase release.
Sjödin
L
L
Department of Drugs, National Board of Health and Welfare, Uppsala, Sweden.
Dahlén
H G
HG
Lund
P E
PE
Gylfe
E
E
D000681:Amylases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002108:Ceruletide / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D010179:Pancreas / Q000201:enzymology / Q000378:metabolism*; D010477:Perfusion; D012844:Sincalide / Q000494:pharmacology; D013373:Substance P / Q000494:pharmacology
D013373:Substance P; D002108:Ceruletide; D002217:Carbachol; D000681:Amylases; D012844:Sincalide; D002118:Calcium