Postprandial plasma 5-hydroxytryptamine in diarrhoea predominant irritable bowel syndrome: a pilot study.
BACKGROUND
Increased concentrations of 5-hydroxytryptamine (5-HT) can be detected in the systemic circulation after a meal and may be involved in the physiological control of gastrointestinal motility. Abnormalities of 5-HT release after a meal might explain some of the postprandial symptoms associated with the irritable bowel syndrome (IBS).


OBJECTIVE
To investigate the effect of a standard meal on plasma 5-HT and urinary 5-hydroxyindole acetic acid (5-HIAA) concentrations in patients with diarrhoea predominant IBS and in healthy volunteers.


METHODS
After an overnight fast, six volunteers and five patients with IBS were given a carbohydrate-rich meal. Blood and urine samples were taken before and for four hours after the meal. Platelet-poor plasma 5-HT and urinary 5-HIAA were analysed by reversed phase high performance liquid chromatography with fluorometric detection. 5-HIAA was expressed as a ratio with urinary creatinine concentration, which was measured by spectrophotometry.


RESULTS
During the four hour postprandial period, 5-HT concentrations were significantly higher in patients with IBS than in healthy volunteers at 0.5 hours (p < 0.05), 2 hours (p < 0.05) and 2.5 hours (p < 0.05). 5-HT was not detected in the plasma in the fasting state in patients or volunteers. Median peak 5-HT in patients with IBS (359 (198-796) nmol/l) was significantly greater than volunteers (83 (7-190)) (p < 0.05). "Area under the curve" for 5-HT detection was greater for patients with IBS (317 (138-771)) than for healthy volunteers (51 (4-129); p < 0.05). The duration of the 5-HT peak was significantly longer in patients with IBS (3 (1-3) hours) than in the healthy volunteers (1 (1-1) hours; p < 0.01). Postprandial urinary median 5-HIAA values in controls (5.6 (5.5-5.8) mumol/mmol creatinine) and patients with IBS (3.0 (2.5-6.8) mumol/mmol creatinine) were not significantly different from preprandial values (controls: 5.9 (5.5-6.6) mumol/mmol creatinine; patients with IBS: (6.2 (2.4-9.3) mumol/mmol creatinine).


CONCLUSIONS
These findings indicate that there may be a difference in the way that 5-HT is released in patients with diarrhoea predominant IBS, and could suggest a possible role for 5-HT in the postprandial symptoms of these patients.
Bearcroft
C P
CP
Digestive Diseases Research Centre, London, UK.
Perrett
D
D
Farthing
M J
MJ
D000293:Adolescent; D000328:Adult; D019540:Area Under Curve; D002851:Chromatography, High Pressure Liquid; D003109:Colonic Diseases, Functional / Q000097:blood* / Q000652:urine; D003404:Creatinine / Q000652:urine; D003967:Diarrhea / Q000097:blood*; D004435:Eating; D005260:Female; D005470:Fluorometry; D006801:Humans; D006897:Hydroxyindoleacetic Acid / Q000652:urine; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D019518:Postprandial Period; D012701:Serotonin / Q000097:blood*; D018709:Statistics, Nonparametric
D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D003404:Creatinine