Calcium involvement in the muscarinic response of the gastric parietal cell.
The influence of extracellular Ca2+ on the mediation of carbachol stimulation in isolated rabbit gastric parietal cells was studied. Removing Ca2+ from extracellular medium caused a 42% decrease of the aminopyrine accumulation due to carbachol with the same EC50 value (approximately 5 microM). A short time depletion in extracellular calcium suppressed the carbachol-dependent Ca2+ influx without affecting Ca2+ release from internal stores (fura-2 measurements). Similarly, the production of inositol phosphates under cholinergic stimulation was reduced by 29%. A rapid increase in Ins(1,4,5)P3 was obtained 5 s after carbachol stimulation, and this increase was not changed in Ca2(+)-depleted medium. In contrast, a 20 min incubation with carbachol caused a 50% reduction in both basal and carbachol-stimulated inositol phosphate accumulations. In conclusion, phospholipase C activation, intracellular Ca2+ release and aminopyrine accumulation were sequentially observed following carbachol stimulation of the isolated gastric parietal cell and extracellular calcium contributed to sustain this acid secretory response.
Leonard
A
A
Laboratoire de Biochimie des Membranes du CNRS UPR-41, INSERM U-249, Faculté de Pharmacie, Montpellier, France.
Guillon
G
G
Choquet
A
A
Bali
J P
JP
D000632:Aminopyrine / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology*; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D007295:Inositol Phosphates / Q000378:metabolism; D007700:Kinetics; D010295:Parietal Cells, Gastric / Q000378:metabolism*; D011817:Rabbits; D011976:Receptors, Muscarinic / Q000378:metabolism*
D007295:Inositol Phosphates; D011976:Receptors, Muscarinic; D000632:Aminopyrine; D002217:Carbachol; D002118:Calcium