Regional Distribution of Peptide YY Concentrations in Human Lower Gastrointestinal Mucosa

ABSTRACT

PURPOSE: Peptide YY is composed of 36 amino acids, and its functions are suppression of gastric acid secretion, delay of gastric emptying, increase of intestinal motility, inhibition of pancreatic exocrine secretion, and enhanced postprandial colonic absorption of water and electrolyte. PYY is released from PYY cells, which are mainly distributed in the ileum and colon, in response to the presence of intraluminal lipids. This study was designed to determine the regional distribution of PYY in the normal human ileum, colon, rectum, and anal canal by studying mucosal concentrations. METHODS: Fresh tissues were obtained from specimens of segmental resections of the small bowel, colectomies, ileostomies, and abdominoperineal resections for the management of colonic or rectal carcinomas or benign diseases of the bowel. Only specimens devoid of advanced luminal obstruction were included. Mucosa was separately recruited by microdissection of frozen sections. Radioimmunoassays were performed using the methods of Adrian et al. RESULTS: The concentration of PYY was highest at 25 cm proximal to the ileocecal valve in the ileum (307.6 pmol/ g) and in the upper rectum at the colon (653.1 pmol/g). The concentration of PYY was 27.3 pmol/g in the anal canal distal to the dentate line. A clear differential distribution of PYY was shown in the ileum and colon. CONCLUSIONS: This study showed PYY was present in large amounts in the mucosa of the ileum and colon, with high concentrations in locations 25 cm proximal to ileocecal valve and in the upper rectum, respectively. The trend of regional differences in PYY in the colonic mucosa probably reflects local differences in functions, such as absorption and storage. Also, the peak concentration in the ileum at 25 cm proximal to ileocecel valve suggests that this region is the most abundant production site of PYY in the ileum.