Postprandial platelet-poor plasma 5-hydroxytryptamine concentrations during diarrhea and constipation periods of alternatingtype irritable bowel syndrome patients

Abstract

Background/aims: Our aim was to measure concentrations of platelet-poor plasma 5-hydroxytryptamine and to assess any relationship with gastrointestinal symptomatology under fasting and fed conditions in alternating-type irritable bowel syndrome during both constipation and diarrhea periods separately. Results of the two periods were compared with each other as well as with the results of the controls.

Methods: Nine patients with alternating diarrhea and constipation symptoms and 9 controls were enrolled. Serial plasma 5-hydroxytryptamine was measured for 1 hour under fasting and for 3 hour after a standard carbohydrate meal. Patients underwent the same measurements during constipation and diarrhea periods separately. Serum 5-hydroxytryptamine concentrations were determined by high-performance liquid chromatography. Symptomatology was assessed throughout the study.

Results: Patients exhibited higher concentrations of platelet-poor plasma 5-hydroxytryptamine under fed conditions during diarrhea, especially at postprandial 30 minutes (p<0.05) compared with concentrations during constipation. Increases in postprandial plasma 5-hydroxytryptamine concentrations relative to fasting concentrations were also significantly higher during the diarrhea period than during constipation and in controls (p<0.05). Although there was no significant correlation between plasma 5-hydroxytryptamine concentrations and symptom scores, patients had worse postprandial symptomatology during diarrhea compared with controls (p<0.05).

Conclusions: Platelet-poor plasma 5-hydroxytryptamine concentrations after meal ingestion differ between constipation and diarrhea periods in alternating-type irritable bowel syndrome. Postprandial symptomatology is also more prominent during diarrhea. These results suggest that differences in plasma levels of serotonin between diarrhea and constipation may underlie the pathogenesis of alternating-type irritable bowel syndrome and could be involved in some aspects of symptomatology.