Bombesin-induced gastrin release from canine G cells is stimulated by Ca2+ but not by protein kinase C, and is enhanced by disruption of rho/cytoskeletal pathways.
Isolated canine G cells in primary culture have been used to study calcium, protein kinase C (PKC), and rho/cytoskeletal-dependent intracellular pathways involved in bombesin- stimulated gastrin release. A method to obtain highly purified G cells by culture (64% G cells) after flow cytometry on elutriated fractions of cells from digested canine gastric antral mucosa has been developed. Pretreatment of G cells with thapsigargin (10(-8)-10(-6) M) and release experiments in Ca2+-containing or -depleted media showed that influx of Ca2+ into the cells and not acute release from intracellular stores plays an important role in bombesin-stimulated gastrin release. Inhibition of PKC by the specific inhibitor GF 109 203X did not affect bombesin-stimulated release. Rho, a small GTP-binding protein that regulates the actin cytoskeleton, is specifically antagonized by Clostridium botulinum C3 exoenzyme. C3 (10 microg/ml) enhanced basal and bombesin-stimulated gastrin release by 315 and 266%, respectively. The importance of the cytoskeleton for regulation of gastrin release was emphasized by a more pronounced release of gastrin when the organization of the actin cytoskeleton was disrupted by cytochalasin D (5 x 10(-)7 and 10(-)6 M). Wortmannin, a potent inhibitor of phosphoinositide-3-kinase, did not alter bombesin-stimulated gastrin release. Thus, it is concluded that bombesin-induced gastrin release from canine G cells is stimulated by Ca2+ but not by PKC, and is enhanced by disruption of rho/cytoskeletal pathways.
Seensalu
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CURE: Digestive Diseases Research Center, Department of Medicine, UCLA, Los Angeles, California 90073, USA.
Avedian
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Barbuti
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Song
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Slice
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Walsh
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JH
D036002:ADP Ribose Transferases / Q000494:pharmacology; D000818:Animals; D001839:Bombesin / Q000494:pharmacology*; D001905:Botulinum Toxins; D002118:Calcium / Q000502:physiology*; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000502:physiology*; D004285:Dogs; D005434:Flow Cytometry; D005753:Gastric Mucosa / Q000187:drug effects* / Q000378:metabolism; D005755:Gastrins / Q000378:metabolism*; D011493:Protein Kinase C / Q000502:physiology*; D012234:Rho Factor / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D005755:Gastrins; D012234:Rho Factor; D015638:Cytochalasin D; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D011493:Protein Kinase C; D001905:Botulinum Toxins; D013755:Tetradecanoylphorbol Acetate; D001839:Bombesin; D002118:Calcium