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Abstract
A radioimmunoassay has been developed for the new intestinal hormonal peptide tyrosine
tyrosine [peptide YY (PYY)]. Peptide YY concentrations were measured in separated
layers of the human gastrointestinal tract, where PYY was found exclusively in the
mucosal epithelium which contained the endocrine cells. Peptide YY was found throughout
the small intestine, in very low concentrations (5 pmol/g) in duodenum (6 pmol/g)
and jejunum (5 pmol/g), but in higher concentrations in the terminal ileum (84 pmol/g).
High concentrations were found throughout the colon (ascending 82 pmol/g, sigmoid
196 pmol/g), being maximum in the rectum (480 pmol/g). The major molecular form of
PYY-like immunoreactivity in human intestine appeared to be identical to pure porcine
hormone, both as judged by gel permeation chromatography and by reverse-phase high-pressure
liquid chromatography. Basal plasma concentrations of PYY were low but rose in response
to food, remaining elevated for several hours postprandially. The known potent biologic
actions of PYY, its high concentrations in gut endocrine cells, and its release into
the circulation after a normal meal suggest that this peptide may function physiologically
as a circulating gut hormone.