Patients with constipation-predominant irritable bowel syndrome (IBS) may have elevated serotonin concentrations in colonic mucosa as compared with diarrhea-predominant patients and subjects with normal bowel habits.
BACKGROUND
Serotonin (5-HT) may play an important role in the regulation of colonic motility in humans. However, it is not known whether alterations in the colonic 5-HT system are involved in the pathophysiology of irritable bowel syndrome (IBS).


METHODS
Colonic mucosal specimens ranging from the ascending colon to the rectum were obtained from patients with diarrhea- or constipation-predominant IBS (n = 7 and n = 8, respectively) and from subjects with normal bowel habits (n = 7) by endoscopic biopsy in order to determine whether patients with different clinical manifestations of IBS have different mucosal disposition of 5-HT. The tissue concentrations of 5-HT and its major metabolite, 5-hydroxyindoleacetic acid, were determined by reversed-phase high-performance liquid chromatography with fluorescence detection.


RESULTS
In all study groups, the mean mucosal 5-HT concentrations obtained from the rectum were significantly (p < 0.05) higher than those obtained from more cephalic regions of the colon. In addition, the overall mean mucosal 5-HT concentrations obtained from patients with constipation-predominant IBS were significantly (p < 0.05) higher than those obtained from the control subjects and patients with diarrhea-predominant IBS. No significant differences were observed in 5-hydroxyindoleacetic acid concentrations among the three groups.


CONCLUSIONS
The mucosal 5-HT concentrations in the colon showed an ascending cephalocaudal gradient in all study groups. Although the mucosal 5-HT concentrations were elevated in patients with constipation-predominant IBS as compared with those with diarrhea-predominant IBS and the control subjects, further studies are necessary to determine whether the elevated mucosal 5-HT is a cause or a result of abnormal colonic motility.
Miwa
J
J
Division of Gastroenterology, International Medical Center of Japan, Tokyo, Japan. jun.miwa@po.toshiba.co.jp
Echizen
H
H
Matsueda
K
K
Umeda
N
N
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D003109:Colonic Diseases, Functional / Q000150:complications / Q000378:metabolism*; D003248:Constipation / Q000150:complications / Q000175:diagnosis / Q000378:metabolism*; D003967:Diarrhea / Q000150:complications / Q000175:diagnosis / Q000378:metabolism; D005260:Female; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011336:Probability; D012680:Sensitivity and Specificity; D012701:Serotonin / Q000032:analysis*
D012701:Serotonin