A gastric housekeeping Cl- channel activated via prostaglandin EP3 receptor-mediated Ca2+/nitric oxide/cGMP pathway.
Prostaglandin E2 (PGE2) has a cytoprotective role in the gastric parietal cell. PGE2 opened a housekeeping basolateral Cl- channel of rabbit gastric parietal cells, the single channel conductance of which was about 0.3 picosiemens. In the present patch-clamp and Fura 2 fluorescence studies, we found that PGE2 increased the intracellular free Ca2+ concentration ([Ca2+]i) and that PGE2-induced opening of the Cl- channel depended on the increase of [Ca2+]i. A novel bifunctional prostaglandin EP3 agonist/EP1 antagonist, 5(Z)-7-[1S, 2S, 3S, 5R)-3-(trans-beta-styren) sulfonamido-6,6-dimethylbicyclo- (3.1.1)hept-2-yl]-5-heptenoic acid, also increased both [Ca2+]i and channel opening. The PGE2-induced effect was mediated via production of nitric oxide (NO); that is, NG-monomethyl-L-arginine, an inhibitor of NO production, markedly inhibited the PGE2-induced channel opening, and nitroprusside, a NO donor, induced the channel opening in the absence of PGE2. Both PGE2 and A23187, Ca2+ ionophore, elevated the cGMP content of isolated parietal cells. The A23187-induced channel opening was abolished by methylene blue, a guanylate cyclase inhibitor. In conclusion, we found that the PGE2-induced opening of the housekeeping Cl- channel in the parietal cell involves the EP3 receptor-mediated increase in [Ca2+]i via a pertussis toxin-sensitive GTP-binding protein, resulting in successive production of NO and cGMP.
Sakai
H
H
Department of Pharmaceutical Physiology, Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Japan.
Kumano
E
E
Ikari
S
S
Takeguchi
N
N
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D018118:Chloride Channels / Q000187:drug effects*; D006152:Cyclic GMP / Q000502:physiology*; D015232:Dinoprostone / Q000494:pharmacology*; D019204:GTP-Binding Proteins / Q000502:physiology; D005753:Gastric Mucosa / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000502:physiology*; D037342:Pertussis Toxin; D011817:Rabbits; D011982:Receptors, Prostaglandin / Q000502:physiology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D018118:Chloride Channels; D011982:Receptors, Prostaglandin; D010566:Virulence Factors, Bordetella; D009569:Nitric Oxide; D000001:Calcimycin; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D006152:Cyclic GMP; D015232:Dinoprostone; D002118:Calcium