Ca2+ metabolism during cholinergic stimulation of acid secretion.
Carbachol-induced changes in 45Ca fluxes and cytosolic free Ca2+ were characterized in rabbit gastric glands and isolated dog parietal cells. Cholinergic stimulation was expressed as changes in the membrane permeability of the parietal cell to Ca2+ without Ca2+ release from intracellular stores. The changes in the membrane permeability to Ca2+ were sustained as long as the cells were exposed to carbachol, independent of extracellular Ca2+, and had the properties of a passive pathway across which Ca2+ distributed according to its chemical gradient. As a consequence of the changes in membrane permeability to Ca2+, carbachol caused a sustained increase in free cytosolic Ca2+ from a resting level of 134 +/- 11 to 533 +/- 81 nM (n = 14). After carbachol stimulation, calcium ions were sequestered in mitochondrial and probably nonmitochondrial compartments. When cell stimulation was terminated by atropine or La3+, the cells restored the resting level of the intracellular Ca2+ activity ([Ca2+]in), independent of uncoupling of mitochondrial oxidation phosphorylation. Reduction in [Ca2+]in was mainly through Ca2+ efflux across the plasma membrane of the parietal cell. Manipulation of intracellular Na+ ion activity in intact cells and studies with basal-lateral membrane vesicles from gastric mucosa indicated the absence of extracellular Na+-intracellular Ca2+ exchange activity in the plasma membrane of the parietal cell. A calmodulin-regulated, ATP-dependent Ca2+ pump that could maintain active Ca2+ extrusion from parietal cells was found in the basal-lateral membrane of the parietal cells.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D002147:Calmodulin / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D005744:Gastric Acid / Q000378:metabolism*; D005753:Gastric Mucosa / Q000378:metabolism; D066298:In Vitro Techniques; D010275:Parasympathetic Nervous System / Q000502:physiology*; D010295:Parietal Cells, Gastric / Q000378:metabolism; D011817:Rabbits
D002132:Calcium Radioisotopes; D002147:Calmodulin; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D004533:Egtazic Acid; D001285:Atropine; D002217:Carbachol; D002118:Calcium