Xenopsin- and neurotensin-like peptides in gastric juice from patients with duodenal ulcers.

Using an anti-serum directed against the COOH-terminal region of neurotensin and an anti-serum raised xenopsin in radioimmunoassays, the presence of neurotensin- and xenopsin-like immunoreactivity in Sep-pak extracts of human gastric juice was demonstrated. An anti-serum directed against the NH2-terminal to central residues of neurotensin and an anti-serum directed against a conformation, present only in the intact peptide, did not detect immunoreactivity in the juice. Infusions of pentagastrin at doses of 0.75 micrograms kg-1 h-1 and 1.5 micrograms kg-1 h-1 resulted in significant (P less than 0.05) increases in the total amount of xenopsin-like, but not neurotensin-like, immunoreactivity released in the juice compared with basal release. No significant differences in the release of xenopsin- or neurotensin-like immunoreactive were observed between patients with selective proximal vagotomy and patients without operation. Analysis by gel permeation chromatography and high performance liquid chromatography demonstrated that both the neurotensin- and xenopsin-like immunoreactivity was heterogeneous and an increase in molecular complexity on pentagastrin-stimulation was observed. As both neurotensin and xenopsin inhibit gastric exocrine activity, the presence of immunochemically related substances in gastric juice may have physiological relevance.