title: Cell volume regulation and apoptotic volume decrease in rat distal colon superficial enterocytes.
abstract: BACKGROUND
  The colon epithelium is physiologically exposed to osmotic stress, and the activation of cell volume regulation mechanisms is essential in colonocyte physiology. Moreover, colon is characterized by a high apoptotic rate of mature cells balancing the high division rate of stem cells.
  
  
  OBJECTIVE
  The aim of the present work was to investigate the main cell volume regulation mechanisms in rat colon surface colonocytes and their role in apoptosis.
  
  
  METHODS
  Cell volume changes were measured by light microscopy and video imaging on colon explants; apoptosis sign appearance was monitored by confocal microscopy on annexin V/propidium iodide labeled explants.
  
  
  RESULTS
  Superficial colonocytes showed a dynamic regulation of their cell volume during anisosmotic conditions with a Regulatory Volume Increase (RVI) response following hypertonic shrinkage and Regulatory Volume Decrease (RVD) response following hypotonic swelling. RVI was completely inhibited by bumetanide, while RVD was completely abolished by high K(+) or iberiotoxin treatment and by extracellular Ca(2+) removal. DIDS incubation was also able to affect the RVD response. When colon explants were exposed to H2O2 as apoptotic inducer, colonocytes underwent an isotonic volume decrease ascribable to Apoptotic Volume Decrease (AVD) within about four hours of exposure. AVD was shown to precede annexin V positivity. It was also inhibited by high K(+) or iberiotoxin treatment. Interestingly, treatment with iberiotoxin significantly inhibited apoptosis progression.
  
  
  CONCLUSIONS
  In rat superficial colonocytes K(+) efflux through high conductance Ca(2+)-activated K(+) channels (BK channels) was demonstrated to be the main mechanism of RVD and to plays also a crucial role in the AVD process and in the progression of apoptosis.
authors: Dept. of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Lecce, Italy.
authors: Stefania
authors: S
authors: Antico
authors: Maria Giulia
authors: MG
authors: Lionetto
authors: Maria Elena
authors: ME
authors: Giordano
authors: Roberto
authors: R
authors: Caricato
authors: Trifone
authors: T
authors: Schettino
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D003106:Colon / Q000166:cytology*; D020895:Enterocytes / Q000166:cytology*; D006861:Hydrogen Peroxide / Q000633:toxicity; D007413:Intestinal Mucosa / Q000166:cytology; D007477:Ions / Q000737:chemistry; D008297:Male; D018613:Microscopy, Confocal; D010455:Peptides / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D007477:Ions; D010455:Peptides; D015221:Potassium Channels; D002034:Bumetanide; C064719:iberiotoxin; D006861:Hydrogen Peroxide; D011188:Potassium; D002118:Calcium