Effect of vasoactive intestinal peptide, somatostatin, neurotensin, cholecystokinin octapeptide, and secretin on intestinal absorption of amino acid in rat.

The effects of vasoactive intestinal peptide (VIP), somatostatin (SRIF), neurotensin (NT), cholecystokinin octapeptide (CCK-8), and secretin (SEC) on the intestinal absorption of amino acid were investigated. Six groups of Wistar rats were studied: (1) controls; (2) VIP treated; (3) SRIF treated; (4) NT treated; (5) CCK-8 treated; (6) SEC treated. [3H]Leucine was given intraluminally through a cannula at the ligament of Treitz, a number of blood samples were obtained through a superior mesenteric vein catheter 1-60 min after administration of [3H]leucine, and the radioactivity of plasma was measured to evaluate the absorption of [3H]leucine. It was shown that VIP and SRIF significantly inhibited the absorption of [3H]leucine (by 59.1% and 38.7%, respectively), whereas NT, CCK-8, and SEC significantly enhanced absorption (by 44.2%, 49.6%, and 39.1%, respectively). Radioimmunoassays of VIP, SRIF, and NT showed that at least some of the hormones or peptides exerted their effects on absorption of leucine at or near their physiological concentrations.