Increase in neurotensin-like immunoreactivity in rat plasma after administration of calcium, bombesin and fat and its inhibition by somatostatin

Abstract

Neurotensin-like immunoreactivity (NTLI) is released from the small intestine into the blood after enteral administration of fat and systemic administration of bombesin. The purpose of the present investigation in the rat was to study the effect of intravenously (i.v.) administered CaCl2 on the plasma concentration of NTLI (p-NTLI) and to investigate the effect of i.v. infusion of somatostatin on basal NTLI release, as well as that stimulated by fat, bombesin and CaCl2. Administration of CaCl2 (5-25 mg X kg-1) increased p-NTLI levels in a significant and dose-dependent manner. In contrast, somatostatin 25-200 ng X min-1) reduced the basal p-NTLI levels, as well as the increase in p-NTLI levels induced by CaCl2 (10 and 25 mg X kg-1), fat (oleic acid, 0.5 ml) and bombesin (25 and 125 pmol X kg-1), in a dose-related manner. Injection of bombesin released immunoreactive material that was indistinguishable from synthetic bovine neurotensin (1-13) upon gel-filtration. This material seemed to be rapidly converted to the more stable metabolite neurotensin (1-8).