Radioimmunoassay, pharmacokinetics, and neuronal release of gastrin-releasing peptide in anesthetized pigs.

Using a newly developed radioimmunoassay for porcine gastrin-releasing peptide in plasma, we studied the pharmacokinetics of this peptide after infusing it into pigs at two dose levels. The disappearance of the peptide from plasma was characterized by two components, a fast one (t 1/2 1.4 min) and a slow one (t 1/2 6.6 min). With the same assay the release of gastrin releasing-peptide from the stomachs of 8 pigs that had been catheterized for selective sampling of fundic and antral blood was studied during vagal and splanchnic stimulation with or without acute adrenalectomy at neutral, acidic, and alkaline intragastric pH. Electrical stimulation of the vagal nerves resulted in a marked increase in both antral and fundic gastrin-releasing peptide release, whereas splanchnic stimulation was without effect. The effects of nerve stimulation were neither influenced by intragastric pH nor by adrenalectomy. Because of its presence in nerves in all layers of the gastric wall, its potent effect on gastrin release, and its release after vagal stimulation, gastrin-releasing peptide is likely to play a role in the vagal control of gastrin release, gastric motility, and acid secretion.