Secretagogue effects on intracellular calcium in pancreatic duct cells.
Regulation of intracellular free calcium ([Ca2+]i) in single epithelial duct cells of isolated rat and guinea pig pancreatic interlobular ducts by secretin, carbachol and cholecystokinin was studied by microspectrofluorometry using the Ca2(+)-sensitive, fluorescent probe Fura-2. Rat and guinea pig duct cells exhibited mean resting [Ca2+]i of 84 nM and 61 nM, respectively, which increased by 50%-100% in response to carbachol stimulation, thus demonstrating the presence of physiologically responsive cholinergic receptors in pancreatic ducts of both species. The carbachol-induced increase in [Ca2+]i involved both mobilization of Ca2+ from intracellular stores and stimulation of influx of extracellular Ca2+. In contrast, neither cholecystokinin nor secretin showed reproducible or sizeable increases in [Ca2+]i. Both rat and guinea pig duct cells showed considerable resting Ca2+ permeability. Lowering or raising the extracellular [Ca2+]i led, respectively, to a decrease or increase in the resting [Ca2+]i. Application of Mn2+ resulted in a quenching of the fluorescence signal indicating its entry into the cell. The resting Ca2+ and Mn2+ permeability could be blocked by La3+ suggesting that it is mediated by a Ca2+ channel.
Stuenkel
E L
EL
Department of Physiology, University of Michigan, Ann Arbor 48109-0622.
Hootman
S R
SR
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology*; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D002766:Cholecystokinin / Q000494:pharmacology*; D006168:Guinea Pigs; D008297:Male; D010183:Pancreatic Ducts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012633:Secretin / Q000494:pharmacology*
D012633:Secretin; D002217:Carbachol; D002766:Cholecystokinin; D002118:Calcium