title: Extracellular nucleotides increase cytosolic free calcium by activating P2u-receptors in single human gastric mucous cells.
abstract: In single human gastric mucous cells extracellular ATP, ATP-gamma-S, ADP and UTP at micromolar concentrations caused a biphasic increase in [Ca2+]i. Consistent with a P2u-receptor the rank-order of potency was ATP > or = UTP > ATP-gamma-S > ADP, and cross-desensitization of the Ca2+ responses occurred between ATP and UTP. The initial transient peak in [Ca2+]i was resistant to extracellular Ca2+ depletion which demonstrates mobilization of internal Ca2+. By contrast, the sustained plateau phase required influx of external Ca2+. Ca2+ influx occurs most likely through a capacitative Ca2+ entry mechanism, which was shown to exist in these cells by experiments performed with thapsigargin. Thus, extracellular ATP and UTP activate a common P2u-receptor most likely coupled to the Ca(2+)-phosphatidylinositol signalling cascade. Extracellular nucleotides from various sources might be an important factor in the regulation of human gastric mucous cells.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D005753:Gastric Mucosa / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D013997:Time Factors; D014544:Uridine Triphosphate / Q000494:pharmacology
chemical_list: D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2; C022571:adenosine 5'-O-(3-thiotriphosphate); D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D002118:Calcium; D014544:Uridine Triphosphate