Dietary Protein Level Influences on Neurotensin-immunoreactive Cells in the Chicken Ileum

Neurotensin is secreted from intestinal N cells in response to the food ingestion. Influences of different dietary protein levels on neurotensin-immunoreactive cells in the chicken ileum were examined by using immunohistochemical and morphometrical techniques. The results showed that dietary protein had an obvious influence on neurotensin-immunoreactive cells in the chicken ileum. Four experimental groups were used, with dietary crude protein (CP) levels of 18% (control), 9%, 4.5% and 0%. Enteroendocrine cells showing neurotensin-immunoreactivity were located in crypts and villous epithelium in all groups. Most of the neurotensin-immunoreactive cells in the villous epithelium showed pyramidal or spindle-like shape with a long cytoplasmic process reaching the intestinal lumen, but cells with round or oval shape were found in the CP4.5% and 0% groups. Frequencies of occurrence of neurotensin-immunoreactive cells in the CP18%, 9%, 4.5% and 0% groups were 42.4±3.3, 36.6±2.2, 30.8±2.6 and 25.4±3.8 (cell count per mucosal area: cells/mm², mean±SD), respectively. There were significant differences in neurotensin-immunoreactive cell frequency between the control and lower CP level, 4.5% and 0%, groups. A significant correlation was found between frequency of occurrence of neurotensin-immunoreactive cells and daily protein intake. These results indicate that ingested protein is likely to be a potential signal for neurotensin production and secretion of N cells in the chicken ileum.