Increased concentration of neurotensin-like immunoreactivity (NTLI) in rat plasma after administration of bombesin and bombesin-related peptides (porcine and chicken gastrin-releasing peptides).

Abstract

The present experiments in the rat were designed to study the effect of bombesin on plasma concentrations of neurotensin‐like immunoreactivity (NTLI), to localize the gastrointestinal site(s) of bornbesin‐induced NTLI release and to compare the effects of bombesin and mammalian and avian bombesin‐related peptides (porcine and chicken gastrin‐releasing peptides) on the plasma concentrations of NTLI. Tail vein injections of bombesin (7.8–500 pmol X kg‐l) increased plasma NTLI in a dose‐related fashion and a peak concentration was obtained one min after the injection. Bombesin was injected into the arteries supplying certain vascular beds. A significant increase in plasma NTLI was found only after injection into the cranial mesenteric artery—the artery which supplies the intestinal area containing the highest concentration of NTLI. lntralurninal instillation of bombesin (1.25 nmol × kg‐1) into the distal part of the small intestine had no effect upon plasma NTLI. but intraperitoneal injection of bombesin (1.25 nmol × kg‐1) caused a significant increase in plasma NTLI. Intravenous injection of natural porcine and chicken gastrin‐releasing peptides and of synthetic porcine gastrin‐releasing peptide caused similar increases in plasma NTLI as bombesin. Chronic bilateral vagotomy did not change the effect of bombesin on plasma NTLI. The results show that the administration of bombesin and mammalian and avian bombesin‐related peptides markedly elevates the plasma concentration of NTLl in the rat and suggest that this elevation is largely due to release of NTLI from the area of the intestine supplied by the cranial mesenteric artery, i.e. jejunum and ileum.