Interaction of Vasoactive Intestinal Peptide with Isolated Intestinal Epithelial Cells from Rat

摘要: Specific binding sites for porcine vasoactive intestinal peptide have been characterized in isolated epithelial cells from rat using 125I-labeled and a variety of physicochemical conditions. At 15°C the reached plateau between 90 240 min incubation was linear function cell concentration up to about 8.8 × 105 cells/ml. Inactivation after 120 did not exceed 30% 15% controls, respectively. Optimal pH around 7.5. 30°C an apparent steady-state could be obtained, inactivation both were higher than those at 15°C. Native competitively inhibited range 0.1 nM–0.1 μM; half-maximal inhibition observed 3.1 nM peptide, as low 0.15 showed significant effect. Kinetics studies Scatchard analysis indicated existence two functionally independent classes sites. There are approximately 1.4 high affinity sites/cell with dissociation constant (Kd) 1.6 1.1 106 Kd 74 nM. Chicken exhibited seven times more competing cells, suggesting possible role aminothreonine residue 28 enhancing affinity. Secretin continuous parallel fashion unlabeled but seventy lower Competition experiments several synthetic analogs secretin that is partially related presence hydrophobic amino acids NH2-terminal hexapeptide sequence molecule. Glucagon gastric inhibitory ineffective displacing 10 μM, These properties receptors together earlier reports on biological actions strongly support concept this may act under physiological conditions regulator small function.