Extracellular ATP activates receptor-operated cation channels in mouse lacrimal acinar cells to promote calcium influx in the absence of phosphoinositide metabolism.
In exocrine acinar cells a variety of neurotransmitters (e.g. acetylcholine) stimulate phosphatidylinositol 4,5-bisphosphate hydrolysis elevating intracellular calcium to activate calcium-dependent membrane currents (outward K+ and inward Cl-). This study shows that in lacrimal acinar cells extracellular application of ATP is also associated with outward and inward current responses; these, however, are not the result of phosphoinositide metabolism. ATP directly activates receptor-operated cation channels which permit influx of Na+ and Ca+ (the inward current). The elevation in [Ca2+]i which results is sufficient to activate the outward K+ current. ATP thus promotes Ca+ influx in the absence of phosphoinositide metabolism.
Sasaki
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MRC Secretory Control Research Group, Liverpool University, UK.
Gallacher
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D000109:Acetylcholine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007765:Lacrimal Apparatus / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009355:Neomycin / Q000494:pharmacology; D010716:Phosphatidylinositols / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000378:metabolism; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D007473:Ion Channels; D010716:Phosphatidylinositols; D011956:Receptors, Cell Surface; D013757:Tetraethylammonium Compounds; D004533:Egtazic Acid; D019789:Tetraethylammonium; D000255:Adenosine Triphosphate; D012964:Sodium; D009355:Neomycin; D000109:Acetylcholine; D002118:Calcium