Constitutive expression of inducible nitric oxide synthase in the normal human colonic epithelium.
BACKGROUND
Inducible nitric oxide synthase (iNOS) in the human colon is considered expressed only in inflammatory states such as ulcerative or collagenous colitis. As subtle iNOS labelling was previously observed in some colonic mucosal biopsies from a heterogeneous group of controls with non-inflamed bowel, we studied whether bowel preparation with bisacodyl or polyethylene glycol prior to sigmoidoscopy might induce iNOS expression.


METHODS
Ten healthy, non-smoking male subjects were investigated. Mucosal biopsies were taken from the sigmoid colon prior to bowel preparation and again 12 h after rectal administration of bisacodyl or polyethylene glycol in randomized order. Expression of iNOS protein was quantified by Western blot analysis and localized by immunohistochemistry.


RESULTS
iNOS was expressed in the colonic mucosal biopsies from all subjects and localized in the epithelial cells, particularly at the luminal border of the epithelial cells and more pronounced in the crypt epithelium. The expression of iNOS was unaffected by bowel preparation with bisacodyl or polyethylene glycol.


CONCLUSIONS
iNOS is constitutively expressed in the normal colonic epithelium. The results suggest that synthesis of iNOS protein is unaffected by bowel preparation with the secretagogue laxative, bisacodyl, or polyethylene glycol.
Perner
A
A
Dept. of Gastroenterology, Herlev Hospital Hospital, Denmark.
Andresen
L
L
Normark
M
M
Rask-Madsen
J
J
D000328:Adult; D001726:Bisacodyl / Q000494:pharmacology; D015153:Blotting, Western; D002400:Cathartics / Q000494:pharmacology; D003106:Colon / Q000201:enzymology*; D006801:Humans; D007150:Immunohistochemistry; D007413:Intestinal Mucosa / Q000201:enzymology*; D008297:Male; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D011092:Polyethylene Glycols / Q000494:pharmacology
D002400:Cathartics; D001726:Bisacodyl; D011092:Polyethylene Glycols; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II