Delineation of the chemomechanosensory regulation of gastrin secretion using pure rodent G cells.
OBJECTIVE
Gastrin is a key regulator of gastric acid secretion. We aimed to isolate pure G cells to identify the mechanistic basis of luminal- and strain-mediated regulation.


METHODS
Using gradient centrifugation and fluorescence-activated cell sorting, rat G cells were prepared and luminal, neural, hormonal, and mechanical activation of secretion and signaling pathways studied.


RESULTS
Pure G-cell preparations (>97%) were isolated. Reverse-transcription polymerase chain reaction identified neural, hormonal, bacterial, and luminal G protein-coupled receptors, and immunostaining visualized specific sweet/bitter receptors and the tastant-associated G protein alpha-gustducin. Gastrin release was stimulated by forskolin (adenosine 3',5'-cyclic monophosphate [cAMP] inducer, 10 micromol/L; >3-fold), potentiated by 3-isobutyl-1-methylxanthine (IBMX; phosphodiesterase type 5 inhibitor and adenosine antagonist, 10 micromol/L) and phorbol myristate acetate (phorbol ester, 10 micromol/L), and inhibited by H-89 (protein kinase A inhibitor, 10 micromol/L), PD98059 (MEK1 inhibitor, 0.1 micromol/L), and wortmannin (phosphatidylinositol 3-kinase inhibitor, 1 nmol/L). Gastrin release was stimulated by neuronal G protein-coupled receptor ligands, pituitary adenylate cyclase-activating protein (20 pmol/L, >8-fold) and bombesin (0.1 micromol/L, 8-fold) through cAMP signaling. The tastants sucralose, glucose, caffeine, denatonium, and the vanilloid receptor activator capsaicin all stimulated secretion (>3-fold), as did bacterial lipopolysaccharides Salmonella enteritidis (0.24 nmol/L, 5-fold) greater than Helicobacter pylori (0.57 micromol/L, 3-fold). Secretion was associated with elevated cAMP levels (approximately 2-fold) and could be inhibited by H-89 and PD98059 and potentiated by IBMX and cholera toxin (250 microg/mL). Bacterially mediated secretion also involved activation of nuclear factor kappaB and the c-Jun-N-terminal kinase pathway. Mechanical strain stimulated (2-fold to 8-fold) gastrin release, and decreasing pH from 7.4 to 5.5 inhibited release. The adenosine receptor 2B antagonist MRS1754 inhibited mechanically induced gastrin release.


CONCLUSIONS
G cells are luminal sampling chemomechanosensory cells whose secretion is regulated by neural, hormonal, luminal, and mechanical factors through protein kinase A activation, cAMP signaling, and mitogen-activated protein kinase phosphorylation.
Kidd
Mark
M
Gastrointestinal Pathobiology Research Group, Department of Gastroenterology, Yale University School of Medicine, New Haven, Connecticut 06520-8062, USA.
Hauso
Øyvind
Ø
Drozdov
Ignat
I
Gustafsson
Bjorn I
BI
Modlin
Irvin M
IM
D000818:Animals; D001427:Bacterial Toxins / Q000494:pharmacology; D002469:Cell Separation; D002470:Cell Survival; D002478:Cells, Cultured; D002628:Chemoreceptor Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D020536:Enzyme Activators / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D019863:Gastrin-Secreting Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D005755:Gastrins / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D040542:Mechanotransduction, Cellular / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D013314:Stress, Mechanical
D001427:Bacterial Toxins; D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D005755:Gastrins; D008070:Lipopolysaccharides; D018377:Neurotransmitter Agents; D043562:Receptors, G-Protein-Coupled; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases