Gastrin-Releasing Peptide: Pharmacokinetics and Effects on Gastro-Entero-Pancreatic Hormones and Gastric Secretion In Normal Men*

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Abstract
Gastrin-releasing peptide (GRP) was infused at two dose levels [GRP I (0–30 min): bolus'dose of 1.41 pmol kg−1, followed by 0.12 pmol kg−1 min−1; GRP II (30–60 min): bolus dose of 5.67 pmol kg−1,followe d by 1.50 pmol kg−1 min−1] to six normal men to study the pharmacokinetics of GRP using a newly developed RIA and the effect of GRP on gastro-entero-pancreatic hormones and gastric acid secretion. The half-life of disappearance of GRP was 2.8 ± 0.4 min (±SEM). The MCR and the apparent space of distribution were 33.0 ± 4.0 ml kg−1 min−1 and 133 ± 31 ml kg−1, respectively. GRP stimulated the secretion of gastrin, pancreatic polypeptide, insulin, glucagon, and glucose-dependent insulinotropic polypeptide in a dose-dependent manner. Gastric acid secretion was stimulated 15 min after the increase in gastrin secretion, suggesting that GRP stimulated gastric acid secretion via release of gastrin. GRP had no significant effect on the secretion of enteroglucagon or neurotensin. In the mammalian gastrointestinal tract, GRP is localized exclusively to nerve tissue. This fact and its potent effects demonstrated here make it a likely candidate for peptidergic nervous control of gastrointestinal function.