Extracellular ATP activates receptor-operated cation channels in mouse lacrimal acinar cells to promote calcium influx in the absence of phosphoinositide metabolism. |
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Authors: | T Sasaki D V Gallacher |
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Institution: | MRC Secretory Control Research Group, Liverpool University, UK. |
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Abstract: | 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. |
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