The distribution of polypeptide YY-like immunoreactivity in rat tissues.

The distribution of peptide YY (PYY)-like immunoreactivity (IR) in rat tissues was determined by specific RIA after extraction with boiled 1 N acetic acid. The high concentration of PYY-IR was observed in the gastrointestinal tract, with concentrations gradually increasing from the duodenum to the end of colon. The concentration of PYY-IR in the colon was 298.7-449.5 pmol/g tissue (approximately 100-200 times more than that in the duodenum). Pituitary and pancreas contained measurable amounts of PYY-IR (6.8 and 6.3 pmol/g tissue). The concentration of PYY-IR in the mucosa was higher than that in the muscular layer in the small intestine, cecum, colon, and rectum. The ratio of the mucosal PYY-IR to the muscular PYY-IR was highest in the distal small intestine (4.7-6.8). Sephadex G-50 gel chromatography of the colon extracts revealed the one PYY-IR peak which corresponds to [125I]PYY. The gradual increase of PYY-IR from the duodenum to the end of the colon is different from the distribution of other known gut peptides.