The effect of peptide YY (PYY) on gastric and pancreatico-biliary secretion was studied in humans. Peptide YY was infused into groups of 6 healthy volunteers at doses of 0.59, 0.20, and 0.064 pmol · kg-1 · min-1. The two higher doses caused a significant suppression of gastric acid and pepsin output during background stimulation with pentagastrin. The middle dose of PYY (0.20 pmol · kg-1 · min-1) that increased plasma PYY levels by 27 ± 2 pM caused a 90% ± 18% (mean ± SEM; p < 0.001) reduction in the incremental gastric volume response to pentagastrin. Similarly this dose of PYY caused a substantial inhibition of the acid (77% ± 14%; p < 0.005) and pepsin (96% ± 22%; p < 0.01) response to pentagastrin; in 2 subjects, pepsin output fell to below basal levels. In contrast, the highest dose of PYY (0.62 pmol · kg-1 · min-1) had no significant influence on duodenal juice volume, output of bicarbonate, trypsin, or bilirubin during low dose stimulation with secretin (0.25 pmol · kg-1 · min-1) and cholecystokinin-8 (0.15 pmol · kg-1 · min-1). Thus PYY concentrations in the circulation similar to those seen after the ingestion of food cause a marked reduction in gastric secretion. This peptide should therefore be considered as one of the possible candidates for the classical enterogastrone.
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