Serotonin and serotonin transporter in the rectum of patients with irritable bowel disease

Irritable bowel syndrome (IBS) is a common chronic gastrointestinal disorder, which considerably reduces the quality of life of patients and represents an economic burden to society. In previous studies, the density of serotonin-expressing cells in the rectum of IBS patients did not differ from that of control subjects. The present study was undertaken to investigate the immunoreactivity intensity of serotonin and serotonin-selective reuptake transporter (SERT) in the rectum of IBS patients. A cohort of 50 patients with IBS (41 females and 9 males) were included in the study. Thirty patients had diarrhoea (IBS-D) and 20 had constipation (IBS-C) as the predominant symptom. Twenty-seven subjects were included as controls (19 females and 8 males). Rectal biopsy specimens were immunostained using the avidin-biotin complex method for serotonin and SERT. The immunoreactivity intensity was quantified by computerised image analysis using Olympus cell Sens imaging software. There was no statistical difference of serotonin immunoreactivity intensity in multiple comparisons between controls, IBS-total, IBS-D and IBS-C. Dunn's post test did not reveal any statistical differences among the four groups. There was a significant statistical difference in multiple comparisons between controls, IBS-total, IBS-D and IBS-C regarding the SERT immunoreactivity intensity. SERT immunoreactivity intensity of IBS-total, IBS-D and IBS-C differed significantly from that of controls. It was concluded that the reduced rectal SERT in the IBS patients could be one of the factors contributing to the development of both diarrhoea and constipation in these patients, and that the increasing body of evidence of a genetic abnormality involving SERT underlines the importance of the role of SERT in the pathophysiology of IBS.