sincalide and phosphoramidon

Topics: Astrocytoma; Cell Line; Cell Membrane; Cholecystokinin; Glycopeptides; Humans; Hydrolysis; Kinetics; Neprilysin; Neuroblastoma; Sincalide; Tumor Cells, Cultured

1. Cholecystokinin-octapeptide (CCK-OP, 10(-10)-3 x 10(-6) M) produced a concentration-dependent contractile response in guinea-pig trachea which was enhanced by both the mechanical removal of the epithelium and by indomethacin (10(-5) M), with an EC50 of 6.18 +/- 0.10 x 10(-8) M. 2. Sub-threshold concentrations of CCK-OP, which did not alter the resting tone of the smooth muscle, did not alter responses produced to electrical field stimulation (EFS) or to vagal nerve stimulation in an intact tracheal tube preparation. Atropine (2 x 10(-6) M) did not alter the concentration-response curve to CCK-OP, indicating that CCK-OP contraction is not mediated by cholinergic mechanisms. 3. The inhibition of neutral endopeptidase (endopeptidase-24.11) by phosphoramidon (10(-5) M) gave a leftward shift in the CCK-OP concentration-response curve in tissues with intact epithelium obtained from normal animals, but had no effect in tissues denuded of epithelium or in tissues obtained from animals which had been actively sensitized and challenged with ovalbumin (OA). 4. CCK-OP-induced contractile responses were antagonized by the CCK-receptor antagonists dibutyryl cyclic guanosine monophosphate (pA2 = 4.3) and L-364,718 (pA2 = 9.6). 5. CCK-OP induced bronchoconstriction in large, but not small, human airways and was antagonized by the CCK-receptor antagonist L-364,718. CCK-OP had no effect on cholinergic neural responses elicited by EFS in human airways.

Topics: Animals; Benzodiazepinones; Bronchi; Devazepide; Electric Stimulation; Epithelium; Glycopeptides; Guinea Pigs; Humans; In Vitro Techniques; Indomethacin; Male; Muscle Contraction; Muscle, Smooth; Parasympathetic Nervous System; Respiratory Hypersensitivity; Sincalide; Trachea

Rat kidney membranes were solubilized by Triton X-100 and the CCK-8 degrading peptidases were resolved by chromatography on DEAE-cellulose. Four proteases were detected: two phosphoramidon-sensitive endopeptidases (EC 3.4.24.11), a bestatin-sensitive aminopeptidase and an unidentified enzyme. The pattern of cleavage of CCK-8 and shorter C-terminal fragments by endopeptidase 24.11 was investigated and indicated that the Gly29-Trp30, Trp30-Met31 and Asp32-Phe33 were scissile bonds. However, the cleavage pattern differed markedly from one CCK peptide to another: in the penta- and hexapeptide of CCK the bonds hydrolyzed were either Asp-Phe and Trp-Met or, Asp-Phe and Gly-Trp, respectively. The presence of the sulfate group on the tyrosine residue of CCK-8 influence markedly the nature of the major cleavage fragments produced by the endopeptidase. The major bonds cleaved were Asp-Phe, Trp-Met and Gly-Trp for unsulfated CCK-8, whilst for the sulfated octapeptide, the Trp-Met bond became a minor cleavage site.

Topics: Animals; Chromatography, DEAE-Cellulose; Chromatography, High Pressure Liquid; Endopeptidases; Glycopeptides; Hydrolysis; In Vitro Techniques; Kidney; Membranes; Neprilysin; Peptide Fragments; Protease Inhibitors; Rats; Sincalide; Solubility