Postprandial plasma 5-hydroxytryptamine in diarrhoea predominant irritable bowel syndrome: a pilot study
- aDigestive Diseases Research Centre and St Bartholomew’s and the Royal London School of Medicine and Dentistry, Turner Street, London E1 2AD, UK, bDepartment of Medicine, St Bartholomew’s and the Royal London School of Medicine and Dentistry
- Dr Bearcroft.
- Accepted 31 July 1997
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).
Aim—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) μmol/mmol creatinine) and patients with IBS (3.0 (2.5–6.8) μmol/mmol creatinine) were not significantly different from preprandial values (controls: 5.9 (5.5–6.6) μmol/mmol creatinine; patients with IBS: (6.2 (2.4–9.3) μmol/mmol creatinine).
Conclusion—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.