Enterochromaffin and serotonin cells are abnormal for patients with colonic inertia

In recent studies, serotonin and several gut peptides have been shown to serve as regulators of colonic transit. Thus, the distribution, density, and intensity of cells secreting serotonin or certain gut peptides could be abnormal in patients with colonic inertia. The aim of this study was to evaluate the distribution, density, and staining intensity of enterochromaffin and serotonin cells in the colonic mucosa of patients with colonic inertia compared with a control group.

Between 1993 and 1998 tissue blocks from the right and left side of the colon were obtained in 19 consecutive patients (18 females; mean age, 43.7 +/- 11.5 years) who underwent subtotal colectomy for colonic inertia. The control group consisted of colonoscopic biopsies from the right and left colon of 15 patients (all females; mean age, 52.7 +/- 16.5 years) for indications other then constipation, inflammatory bowel diseases, or carcinoma. Immunocytochemical staining of enterochromaffin and serotonin cells were performed on 4 microm tissue sections with the primary rabbit antibody against chromogranin A or serotonin, and the biotinylated secondary antibody and enzyme-labeled-streptavidin. The average cell number per microscopic field (x200) was calculated and the proportion of cells with various staining distribution was expressed as the percentage of the entire positive cell population as low, moderate, and high intensity. Student's t-test and chi-squared test were used for statistical analysis, with significance level set at P < 0.05.

The quantity of both enterochromaffin cells (16.8 +/- 10.2) and serotonin cells (12.1 +/- 6.4) in the mucosa of the left colon in patients with colonic inertia was significantly higher when compared with the right side of the colon (enterochromaffin cells, 9.4 +/- 6.0; serotonin cells, 7.8 +/- 3.6; P < 0.01). The percentage of both types of cells with low staining intensity was increased, whereas the cells with high and moderate staining intensity were decreased (P < 0.01) in the left colon as compared with the right. The number of enterochromaffin cells in left-sided colonic mucosa was significantly higher in the colonic inertia group than in the control group (16.8 +/- 10.1 vs. 10.4 +/- 6.0; P < 0.05). Moreover, the numbers of serotonin cells in both the right and left colon was also significantly higher in the colonic inertia group than in the control group (right, 7.8 +/- 3.6 vs. 4.1 +/- 2.4; left, 12.1 +/- 6.4 vs. 5.8 +/- 3.7; P < 0.01). In both sides of the colon, the percentage of enterochromaffin and serotonin cells with low staining was significantly higher, whereas percentage of those cells with high or moderate staining was significantly lower in the colonic inertia group than in the control group. In the colonic inertia group there was a significantly positive correlation between numbers of enterochromaffin and serotonin cells (right side, P < 0.01; left side, P < 0.05).

In patients with colonic inertia, the number of both enterochromaffin and serotonin cells are significantly increased in the colonic mucosa, especially in the left colon. As indicated by staining distribution, enterochromaffin and serotonin cells contain significantly less hormone than do the same cells in the control group.