Mobilization of intracellular calcium by methacholine and inositol 1,4,5-trisphosphate in rat parotid acinar cells.
In the rat parotid acinar cell, methacholine caused an increase in [Ca2+]i as determined by quin-2 fluorescence. The increase in [Ca2+]i was initially independent of, and subsequently dependent on, the presence of extracellular Ca2+, indicating mobilization of intracellular Ca2+, as well as activation of Ca2+ entry. Methacholine mobilization of the internal Ca2+ pool and stimulation of the initial transient phase of K+ efflux have similar concentration dependencies; the EC50 value for Ca2+ mobilization is 80 nmol/L, the EC50 value for K+ efflux is 200 nmol/L. In a permeable parotid cell preparation, inositol 1,4,5-trisphosphate, inositol 2,4,5-trisphosphate, and inositol 4,5-bisphosphate were able to release Ca2+ from an ATP-dependent, oligomycin-insensitive pool. These observations, when taken with the previous finding that methacholine stimulates Ca-independent inositol trisphosphate formation, support the view that inositol 1,4,5-trisphosphate acts as a second messenger mediating the release of an intracellular Ca2+ pool following muscarinic receptor activation in the parotid gland.
Aub
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Putney
J W
JW
D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D001826:Body Fluids / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects; D003593:Cytoplasm / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000494:pharmacology*; D007424:Intracellular Fluid / Q000378:metabolism*; D016210:Methacholine Chloride; D008688:Methacholine Compounds / Q000494:pharmacology*; D010306:Parotid Gland / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D051381:Rats; D013403:Sugar Phosphates / Q000494:pharmacology*
D000634:Aminoquinolines; D007295:Inositol Phosphates; D008688:Methacholine Compounds; D013403:Sugar Phosphates; D016210:Methacholine Chloride; D015544:Inositol 1,4,5-Trisphosphate; C035739:Quin2; D011188:Potassium; D002118:Calcium