Gastroenterology

Gastroenterology

Volume 135, Issue 2, August 2008, Pages 632-641
Gastroenterology

Basic—Liver, Pancreas, and Biliary Tract
Direct Activation of Cytosolic Ca2+ Signaling and Enzyme Secretion by Cholecystokinin in Human Pancreatic Acinar Cells,

https://doi.org/10.1053/j.gastro.2008.05.026Get rights and content

Background & Aims: Cholecystokinin (CCK) has been thought to act only indirectly on human pancreatic acinar cells via vagal nerve stimulation, rather than by direct CCK receptor activation as on rodent pancreatic acinar cells. We tested whether CCK (CCK-8 and human CCK-58) can act directly on human pancreatic acinar cells. Methods: Human acinar cells were freshly isolated from pancreatic transection line samples, loaded with Fluo4-AM or quinacrine, and examined for Ca2+, metabolic and secretory responses to CCK-8, human CCK-58, or acetylcholine with confocal microscopy. Results: CCK-8 and human CCK-58 at physiologic concentrations (1–20 pmol/L) elicited rapid, robust, oscillatory increases of the cytosolic Ca2+ ion concentration, showing apical to basal progression, in acinar cells from 14 patients with unobstructed pancreata. The cytosolic Ca2+ ion concentration increases were followed by increases in mitochondrial adenosine triphosphate production and secretion. CCK-elicited Ca2+ signals and exocytosis were not inhibited by atropine (1 μmol/L) or tetrodotoxin (100 nmol/L), showing that CCK was unlikely to have acted via neurotransmitter release. CCK-elicited Ca2+ signals were inhibited reversibly by caffeine (5-20 mmol/L), indicating involvement of intracellular inositol trisphosphate receptor Ca2+ release channels. Acetylcholine (50 nmol/L) elicited similar Ca2+ signals. Conclusions: CCK at physiologic concentrations in the presence of atropine and tetrodotoxin elicits cytosolic Ca2+ signaling, activates mitochondrial function, and stimulates enzyme secretion in isolated human pancreatic acinar cells. We conclude that CCK acts directly on acinar cells in the human pancreas.

Section snippets

Collection of Human Pancreatic Samples

The study was approved by the Liverpool Adult Local Research Ethics Committee (Reference: 03/12/242/A) and written informed consent for sampling was obtained from all patients before surgery. Sampling for these experiments was restricted to patients undergoing surgery for left-sided or small unobstructing pancreatic tumors in otherwise normal pancreata, because preliminary experiments showed that samples from patients with ductal obstruction (eg, from pancreatic cancer) or chronic pancreatitis

Characteristics of Patients, Pancreatic Samples, and Acinar Cell Isolates

Pancreatic samples were donated by 14 patients (mean age, 59 y; range, 25–82 y) undergoing surgery between November 2005 and February 2008 (Table 1). Histopathologic examination of the excised specimen at the pancreatic transection line confirmed normal pancreatic histology in every case, but for mild fibrosis in 4. Isolated acinar cells typically showed excellent morphology, with strong polarity delineated by a distinct granular region in the apical pole of each cell, and no intracellular

Discussion

Our data show that 2 different forms of CCK, CCK-8 and human CCK-58, activate human pancreatic acinar cells at a range of CCK concentrations normally expected in vivo,13 generating robust and reversible intracellular Ca2+ signals that are followed by stimulation of mitochondrial metabolism and exocytosis of digestive enzymes, shown here in real time. Pancreatic enzyme secretion occurs by exocytosis and it is well established in general, as in the pancreas, that exocytosis is initiated by an

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    J.A.M. and D.N.C. contributed equally to this work.

    This work was supported by Programme, Cooperative, and Component grants from the Medical Research Council (UK), and by National Institutes of Health grants DK 33850 (J.R.R.), and DK 37482 (G.M.G.), by the Veterans Administration Research Service, and by the National Institutes of Health CURE: Digestive Diseases Research Center grant DK41301. O.H.P. is a Medical Research Council Professor; J.M. was, and R.M. is, supported by an Amelie Waring Clinical Research Fellowship from CORE; and E.M. is supported by a Clinical Training Fellowship from the Royal College of Surgeons of England.

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