title: Calcium responses in subserosal interstitial cells of the guinea-pig proximal colon.
abstract: BACKGROUND
  In the subserosal layer between the longitudinal muscle layer and mesothelium, heterogeneous populations of interstitial cells are distributed. As the distribution of nerve elements in this layer is sparse as compared with the nerve plexus layer or tunica muscularis, there may be unique communication among subserosal interstitial cells (SSICs). This study aimed to explore functional properties of SSICs.
  
  
  METHODS
  In subserosal preparations of the guinea-pig proximal colon, changes in intracellular Ca(2+) ([Ca(2+) ]i ) were visualized using Fluo-4 Ca(2+) imaging. Immunohistochemistry was also performed to identify the SSICs exhibiting Ca(2+) transients.
  
  
  RESULTS
  A majority of SSICs responded to adenosine triphosphate (ATP, 10 μM) by increasing [Ca(2+) ]i , but remained quiescent during the application of acetylcholine (10 μM). ATP-induced Ca(2+) responses were mimicked by adenosine 5'-diphosphate (10 μM), MRS2365 (10 nM) but not α, β-methylene ATP (10 μM) or uridine triphosphate (10 μM), and could be reproduced in Ca(2+) -free solution, suggesting that ATP acts via P2Y receptors, most likely P2Y1 subtype, but not P2X receptors. Live staining of the same preparations after Ca(2+) imaging indicated the ATP-sensitive SSICs were not positive for c-Kit antibody, a specific marker for gastrointestinal interstitial cells of Cajal (ICC). Immunohistochemistry identified vimentin (mesenchymal cell marker)+/Kit- and SK3 (fibroblast-like cell (FLC) marker)+/Kit- cells that had a similar morphology to the ATP-sensitive SSICs in Ca(2+) imaging.
  
  
  CONCLUSIONS
  A majority of the SSICs in the guinea-pig proximal colon, presumably FLC, are capable of responding to ATP and thus may contribute to smooth muscle relaxation upon stimulation with ATP released from non-neuronal cells.
authors: Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Mizuho-ku, Nagoya, Japan; Japan Society for the Promotion of Science, Chiyoda-ku, Tokyo, Japan.
authors: H
authors: H
authors: Tamada
authors: H
authors: H
authors: Hashitani
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000502:physiology*; D003106:Colon / Q000737:chemistry / Q000166:cytology* / Q000502:physiology*; D004848:Epithelium / Q000737:chemistry / Q000502:physiology; D006168:Guinea Pigs; D056885:Interstitial Cells of Cajal / Q000737:chemistry / Q000502:physiology*; D008297:Male; D032389:Myocytes, Smooth Muscle / Q000737:chemistry / Q000502:physiology*; D009924:Organ Culture Techniques
keywords: ATP; c-Kit; intracellular Ca2+; proximal colon; subserosa