Objective: To investigate the changes of the mast cells (MCs) and substance P (SP), and to elucidate their possible roles in visceral hypersensitivity in patients with irritable bowel syndrome (IBS).
Methods: In 22 diarrhea-predominant IBS, 20 constipation-predominant IBS and 19 controls, the biopsies were carried out from the terminal ileum, the ileocecal junction, the ascending colon, and the sigmoid colon. The MCs and the SP-ergic nerve terminals, SP receptor (SPR) cells were stained by histochemistry and immunohistochemistry respectively, and the results were investigated qualitatively and quantitatively by color image analyzer. The biopsies of the ICJ and the sigmoid colon were measured by radioimmunoassay. The structure relation between the MCs and SP-ergic terminals, SPR-ergic cells were studied through an ultramicroscopy using in situ embedding technique and a light microscopic study in serial sections respectively.
Results: The number of MCs in the terminal ileum, the ileocecal junction, and the ascending colon were significantly elevated in IBS patients (P < 0.01), and the MCs in IBS have great variations. Significantly increased the SP-ergic nerve terminals were found in patients with IBS of intestine compared with the control. The correlation between mucosal MC and the SP-ergic nerve terminals was found, and MCs were close to these terminals in lamina propria, which were demonstrated SP-ergic nerve terminals. Some MCs were demonstrated to be SPR-positive cells.
Conclusions: The MCs and SP of intestinal mucosa may play a central role in the gut hypersensitivity in both motor response and visceral perception in IBS.