title: Capacitative calcium entry supports calcium oscillations in human embryonic kidney cells.
abstract: Treatment of human epithelial kidney (HEK293) cells with low concentrations of the muscarinic agonist methacholine results in the activation of complex and repetitive cycling of intracellular calcium ([Ca(2+)](i)), known as [Ca(2+)](i) oscillations. These oscillations occur with a frequency that depends on the concentration of methacholine, whereas the magnitude of the [Ca(2+)](i) spikes does not. The oscillations do not persist in the absence of extracellular Ca(2+), leading to the conclusion that entry of Ca(2+) across the plasma membrane plays a significant role in either their initiation or maintenance. However, treatment of cells with high concentrations of GdCl(3), a condition which limits the flux of calcium ions across the plasma membrane in both directions, allows sustained [Ca(2+)](i) oscillations to occur. This suggests that the mechanisms that both initiate and regenerate [Ca(2+)](i) oscillations are intrinsic to the intracellular milieu and do not require entry of extracellular Ca(2+). This would additionally suggest that, under normal conditions, the role of calcium entry is to sustain [Ca(2+)](i) oscillations. By utilizing relatively specific pharmacological manoeuvres we provide evidence that the Ca(2+) entry that supports Ca(2+) oscillations occurs through the store-operated or capacitative calcium entry pathway. However, by artificial introduction of a non-store-operated pathway into the cells (TRPC3 channels), we find that other Ca(2+) entry mechanisms can influence oscillation frequency in addition to the store-operated channels.
authors.affiliation: National Institute of Environmental Health Sciences/NIH, PO Box 12233, Research Triangle Park, NC 27709, USA. bird@niehs.nih.gov
authors.forename: Gary St J
authors.initials: GS
authors.lastname: Bird
authors.forename: James W
authors.initials: JW
authors.lastname: Putney
mesh_terms: D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D025802:Electric Capacitance; D005682:Gadolinium / Q000008:administration & dosage*; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D007668:Kidney / Q000187:drug effects / Q000196:embryology / Q000502:physiology*; D007700:Kinetics; D008657:Metabolic Clearance Rate; D016210:Methacholine Chloride / Q000008:administration & dosage*
chemical_list: D015220:Calcium Channels; D016210:Methacholine Chloride; D005682:Gadolinium; C038958:gadolinium chloride; D002118:Calcium