title: ATP enhances spontaneous calcium activity in cultured suburothelial myofibroblasts of the human bladder.
abstract: BACKGROUND
  Suburothelial myofibroblasts (sMF) are located underneath the urothelium in close proximity to afferent nerves. They express purinergic receptors and show calcium transients in response to ATP. Therefore they are supposed to be involved in afferent signaling of the bladder fullness. Since ATP concentration is likely to be very low during the initial filling phase, we hypothesized that sMF Ca(2+) activity is affected even at very low ATP concentrations. We investigated ATP induced modulation of spontaneous activity, intracellular calcium response and purinergic signaling in cultured sMF.
  
  
  RESULTS
  Myofibroblast cultures, established from cystectomies, were challenged by exogenous ATP in presence or absence of purinergic antagonist. Fura-2 calcium imaging was used to monitor ATP (10(-16) to 10(-4) mol/l) induced alterations of calcium activity. Purinergic receptors (P2X1, P2X2, P2X3) were analysed by confocal immunofluorescence. We found spontaneous calcium activity in 55.18% ± 1.65 of the sMF (N = 48 experiments). ATP significantly increased calcium activity even at 10(-16) mol/l. The calcium transients were partially attenuated by subtype selective antagonist (TNP-ATP, 1 µM; A-317491, 1 µM), and were mimicked by the P2X1, P2X3 selective agonist α,β-methylene ATP. The expression of purinergic receptor subtypes in sMF was confirmed by immunofluorescence.
  
  
  CONCLUSIONS
  Our experiments demonstrate for the first time that ATP can modulate spontaneous activity and induce intracellular Ca(2+) response in cultured sMF at very low concentrations, most likely involving P2X receptors. These findings support the notion that sMF are able to register bladder fullness very sensitively, which predestines them for the modulation of the afferent bladder signaling in normal and pathological conditions.
authors: Department of Urology, University of Leipzig, Leipzig, Germany.
authors: Sheng
authors: S
authors: Cheng
authors: Frank Peter
authors: FP
authors: Scigalla
authors: Pietro
authors: P
authors: Speroni di Fenizio
authors: Zhi Geng
authors: ZG
authors: Zhang
authors: Jens-Uwe
authors: JU
authors: Stolzenburg
authors: Jochen
authors: J
authors: Neuhaus
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D058628:Myofibroblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D058913:Purinergic Agonists / Q000494:pharmacology; D058914:Purinergic Antagonists / Q000494:pharmacology; D011983:Receptors, Purinergic / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D001743:Urinary Bladder / Q000166:cytology*; D019459:Urothelium / Q000166:cytology*
chemical_list: D058913:Purinergic Agonists; D058914:Purinergic Antagonists; D011983:Receptors, Purinergic; D000255:Adenosine Triphosphate; D002118:Calcium