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.
Laboratoire de Biochimie des Membranes du CNRS UPR-41, INSERM U-249, Faculté de Pharmacie, Montpellier, France.
A
A
Leonard
G
G
Guillon
A
A
Choquet
J P
JP
Bali
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