Functional TRP and ASIC-like channels in cultured urothelial cells from the rat.
Transient receptor potential (TRP) and acid-sensing ion channels (ASIC) are molecular detectors of chemical, mechanical, thermal, and nociceptive stimuli in sensory neurons. They have been identified in the urothelium, a tissue considered part of bladder sensory pathways, where they might play a role in bladder function. This study investigated functional properties of TRP and ASIC channels in cultured urothelial cells from the rat using patch-clamp and fura 2 Ca(2+) imaging techniques. The TRPV4 agonist 4alpha-phorbol-12,13 didecanoate (4alpha-PDD; 1-5 microM) and the TRPA1/TRPM8 agonist icilin (50-100 microM) elicited transient currents in a high percentage of cells (>70%). 4alpha-PDD responses were suppressed by the TRPV4 antagonist HC-010961 (10 microM). The TRPV1 agonist capsaicin (1-100 microM) and the TRPA1/TRPM8 agonist menthol (5-200 microM) elicited transient currents in a moderate percentage of cells ( approximately 25%). All of these agonists increased intracellular calcium concentration ([Ca(2+)](i)). Most cells responded to more than one TRP agonist (e.g., capsaicin and 4alpha-PDD), indicating coexpression of different TRP channels. In the presence of the TRPV1 antagonist capsazepine (10 microM), changes in pH induced by HCl elicited ionic currents (pH 5.5) and increased [Ca(2+)](i) (pH 6.5) in approximately 50% of cells. Changes in pH using acetic acid (pH 5.5) elicited biphasic-like currents. Responses induced by acid were sensitive to amiloride (10 microM). In summary, urothelial cells express multiple TRP and ASIC channels, whose activation elicits ionic currents and Ca(2+) influx. These "neuron-like" properties might be involved in transmitter release, such as ATP, that can act on afferent nerves or smooth muscle to modulate their responses to different stimuli.
Kullmann
F Aura
FA
Dept. of Pharmacology and Chemical Biology, Univ. of Pittsburgh School of Medicine, E 1340 Biomedical Science Tower, Pittsburgh, PA 15261, USA. flnst2@pitt.edu
Shah
M A
MA
Birder
L A
LA
de Groat
W C
WC
D062565:Acid Sensing Ion Channels; D000818:Animals; D017487:Ankyrins; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling; D002478:Cells, Cultured; D005260:Female; D006863:Hydrogen-Ion Concentration; D008297:Male; D008564:Membrane Potentials; D049990:Membrane Transport Modulators / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D009419:Nerve Tissue Proteins / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism*; D000074025:TRPA1 Cation Channel; D050052:TRPC Cation Channels / Q000187:drug effects / Q000378:metabolism*; D050053:TRPM Cation Channels / Q000378:metabolism; D050916:TRPV Cation Channels / Q000378:metabolism; D013997:Time Factors; D001743:Urinary Bladder / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D019459:Urothelium / Q000187:drug effects / Q000378:metabolism*
D062565:Acid Sensing Ion Channels; D017487:Ankyrins; D015220:Calcium Channels; D049990:Membrane Transport Modulators; D009419:Nerve Tissue Proteins; D015222:Sodium Channels; D000074025:TRPA1 Cation Channel; D050052:TRPC Cation Channels; D050053:TRPM Cation Channels; D050916:TRPV Cation Channels; C480976:Trpa1 protein, rat; C498947:Trpm8 protein, rat; C493922:Trpv1 protein, rat; C486577:Trpv4 protein, rat