Effects of extracellular ATP on cytosolic Ca2+ concentration and secretory responses in rat parotid acinar cells.
At concentrations >50 microM, extracellular ATP dose-dependently increased cytosolic Ca2+ concentration ([Ca2+]i) via activation of P(2Z) purinoceptors in rat parotid acinar cells. This increase in [Ca2+]i is primarily due to entry of Ca2+ from the extracellular medium. Inositol trisphosphate formation and Ca2+ release from intracellular Ca2+ stores were slightly stimulated by ATP. These responses seem to result from the activation of a P2 purinoceptor subtype different from P(2Z) because the maximum responses were induced by much lower concentrations ( <0.25 mM) of ATP than those (> 1 mM) required to produce the maximum activation of Ca2+ entry. ATP did not stimulate amylase release, supporting the view that an increase in [Ca2+]i is not a sufficient stimulus. In addition, ATP evoked a marked K+ release in the presence and absence of extracellular Ca2+, while in carbachol-stimulated cells. only a transient release of K+ was observed in the absence of extracellular Ca2+. The ATP-induced K+ release may be mediated by a mechanism independent of the opening of the Ca(2+)-sensitive K+ channels.
Tojyo
Y
Y
Department of Dental Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Japan.
Tanimura
A
A
Matsui
S
S
Matsumoto
Y
Y
D000255:Adenosine Triphosphate / Q000008:administration & dosage / Q000494:pharmacology*; D000681:Amylases / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000032:analysis* / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects; D002217:Carbachol / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D003600:Cytosol / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D005110:Extracellular Space / Q000201:enzymology*; D007295:Inositol Phosphates / Q000096:biosynthesis; D008297:Male; D018721:Muscarinic Agonists / Q000494:pharmacology; D010306:Parotid Gland / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D011983:Receptors, Purinergic / Q000187:drug effects
D015220:Calcium Channels; D007295:Inositol Phosphates; D018721:Muscarinic Agonists; D015221:Potassium Channels; D011983:Receptors, Purinergic; D000255:Adenosine Triphosphate; D002217:Carbachol; D000681:Amylases; D011188:Potassium; D002118:Calcium