Regulation of Ca(2+) signals in a parotid cell line Par-C5.
The Ca(2+) signaling system in an established immortalized rat parotid acinar cell line, Par-C5, was examined using the Ca(2+)-sensitive fluorescent indicator fura-2 and by measuring inositol 1,4,5-trisphosphate (IP(3)) formation. Agonist-induced increase in intracellular Ca(2+) ([Ca(2+)](i)) by mobilization of intracellular stores and influx across the cell membrane was stimulated by acetylcholine (ACh) and ATP, whereas noradrenaline-(NA)-induced a small [Ca(2+)](i) increase mediated primarily by release from intracellular Ca(2+) stores. [Ca(2+)](i) increase by ACh and ATP was mediated through the phosphoinositide signal pathway since both agonists significantly increased 1,4,5-IP(3) formation and Ca(2+) mobilization was abolished by the phospholipase C inhibitor U73122. In Ca(2+)-free medium, ACh or ATP discharged the IP(3)-sensitive Ca(2+) store and essentially abolished subsequent [Ca(2+)](i) response to thapsigargin (TG). Exposure to ionomycin and monensin after TG induced a further mobilization of Ca(2+), suggesting IP(3)-insensitive stores are present. Furthermore, depletion of IP(3)-sensitive Ca(2+) stores by TG, ACh and ATP enhanced plasmalemmal Ca(2+)-entry pathways. Exposure to tumor necrosis factor-alpha (TNF-alpha), a cytokine associated with lymphocyte invasion of salivary epithelial cells in autoimmune disorders, significantly reduced ACh-stimulated Ca(2+) mobilization. TNF-alpha inhibitory effect on Ca(2+) mobilization was not directly due to an interaction on muscarinic receptors since ACh-induced 1,4,5-IP(3) formation was not altered. These results in the Par-C5 cell line indicate 1) [Ca(2+)](i) is regulated by muscarinic and P2Y-nucleotide receptors and partly by alpha(1)-adrenergic receptors; 2) IP(3)-sensitive and -insensitive Ca(2+) stores exist; 3) Ca(2+) influx activated by ACh, ATP or TG is mediated by the store-operated Ca(2+) entry pathway; and 4) muscarinic agonist-stimulated Ca(2+) mobilization is altered by the cytokine TNF-alpha.
Liu
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Secretory Cell Physiology Laboratory, Department of Pediatrics, University of Texas Health Center, Mail Code 7827, 7703 Floyd Curl Dr., San Antonio, TX 78229-3900, USA.
Mörk
A C
AC
Sun
X
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Castro
R
R
Martinez
J R
JR
Zhang
G H
GH
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D002118:Calcium / Q000819:agonists / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002461:Cell Line, Transformed; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis; D018721:Muscarinic Agonists / Q000494:pharmacology; D010306:Parotid Gland / Q000166:cytology / Q000378:metabolism*; D058910:Purinergic P2 Receptor Agonists; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000502:physiology; D011976:Receptors, Muscarinic / Q000502:physiology; D018048:Receptors, Purinergic P2 / Q000502:physiology; D058473:Receptors, Purinergic P2Y2; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D002120:Calcium Channel Agonists; D018721:Muscarinic Agonists; C546387:P2ry2 protein, rat; D058910:Purinergic P2 Receptor Agonists; D011942:Receptors, Adrenergic, alpha; D011976:Receptors, Muscarinic; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; D014409:Tumor Necrosis Factor-alpha; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium