TY - JOUR T1 - High Affinity Binding of [<sup>3</sup>H]Propionyl-[Met(O<sub>2</sub>)<sup>11</sup>]Substance P(7–11), a Tritiated Septide-Like Peptide, in Chinese Hamster Ovary Cells Expressing Human Neurokinin-1 Receptors and in Rat Submandibular Glands JF - Molecular Pharmacology JO - Mol Pharmacol SP - 120 LP - 127 DO - 10.1124/mol.52.1.120 VL - 52 IS - 1 AU - Sandrine Sagan AU - Jean-Claude Beaujouan AU - Yvette Torrens AU - Monique Saffroy AU - Gérard Chassaing AU - Jacques Glowinski AU - Solange Lavielle Y1 - 1997/07/01 UR - http://molpharm.aspetjournals.org/content/52/1/120.abstract N2 - Propionyl-[Met(O2)11]substance P(7–11) [ALIE-124 or propionyl-[Met(O2)11]SP(7–11)] has been designed as a septide-like ligand adequate for tritiation and, therefore, adequate for binding studies. In Chinese hamster ovary (CHO) cells expressing human tachykinin neurokinin (NK)-1 receptors, ALIE-124 displaced [3H][Pro9]substance P (SP) from its binding site at micromolar concentrations. However, ALIE-124 stimulated phosphatidylinositol hydrolysis, as previously shown for septide-like peptides. With [3H]ALIE-124 (95 Ci/mmol), we have been able to reveal a high affinity binding site in CHO cells (Kd = 6.6 ± 1.0 nm), with a low maximal binding capacity. [3H]ALIE-124 specific maximal binding represented only 15–20% of that observed with [3H][Pro9]SP in CHO cells. Septide-like peptides, including septide and NKA, were potent competitors (in the nanomolar range) of [3H]ALIE-124 specific binding site. Interestingly, SP and [Pro9]SP were also potent competitors, with 10-fold greater potency for sites labeled with [3H]ALIE-124 than for sites labeled with [3H][Pro9]SP. The NK-1 antagonist RP 67580 also showed a higher potency for [3H]ALIE-124 than for [3H][Pro9]SP-specific binding sites. NKB and [Lys5,methyl-Leu9,Nle10]NKA(4–10) displaced [3H]ALIE-124 binding but with lower potency, whereas senktide had no affinity. The existence of [3H]ALIE-124 specific binding sites was also demonstrated in rat submandibular gland. In this tissue, [3H]ALIE-124 specific maximal binding was higher, reaching 40–50% of that achieved with [3H][Pro9]SP. ER -