The reversible combination of a ligand with specific sites on the surface of a receptor is one of the most important processes in biochemistry. A classic equation with a useful simple graphical method was introduced to obtain the equilibrium constant, Kd, and the maximum density of receptors, Bmax. The entire 125I-labeled ligand binding experiment includes three parts: the radiolabeling, cell s...

Radioligand assays were performed to demonstrate the presence of a receptor for mesotocin (MT) in the membrane fractions of the kidney of the hen. Specific [125I]MT bindings were decreased by the presence of Mg2+ and Ca2+, increased by the presence of EDTA, increased during the first 4 h of incubation and then reached a plateau, and increased with the increase in the protein concentration from ...

The dopamine D2 receptor subtype attracts considerable attention in research on the patophysiology and drug treatment of several neuropsychiatric disorders, such as schizophrenia and Parkinson’s disease. The brain imaging technology Positron Emission Tomography (PET) has since long allowed for reliable quantification of the high density of dopamine D2 receptors in large brain structures such as...

Radioligand binding studies with [(3)H](2E)-(5-hydroxy-5,7,8,9-tetrahydro-6H-benzo[a][7]annulen-6-ylidene) ethanoic acid ([(3)H]NCS-382), an antagonist of gamma-hydroxybutyric acid (GHB) receptor, revealed specific binding sites in the rat cerebral cortex and hippocampus. However, there was very little binding in the rat cerebellum, heart, kidney, liver, and lung membranes. Binding was rapid an...

The 5-hydroxytryptamine receptor of type 3 was investigated by fluorescence correlation spectroscopy (FCS). Binding constants of fluorescently labeled ligands, the stoichiometry, and the mass of the receptor are readily accessible by this technique, while the duration of measurement is on the order of seconds to minutes. The receptor antagonist 1,2,3, 9-tetrahydro-3-[(5-methyl-1H-imidazol-4-yl)...

Previous work from our laboratory indicates that bile acids, specifically lithocholic acid conjugates, interact with muscarinic receptors on gastric chief cells. Structural similarities between acetylcholine and lithocholyltaurine suggest a potential molecular basis for their interaction with the same receptor. We synthesized a hybrid molecule consisting of the steroid nucleus of lithocholyltau...

We have investigated the binding of soluble tenascin-C (TN-C) to several cell lines using a radioligand binding assay. Specific binding was demonstrated to U-251MG human glioma cells and to a line of bovine aortic endothelial cells, but hamster fibroblasts showed no specific binding. Recombinant proteins corresponding to specific domains of TN-C were used to map the binding site(s) in TN-C. The...

The angiotensin II subtype 1 receptor (AT(1)R) has been linked to the development and progression of renovascular hypertension. In this study we applied a pig model of renovascular hypertension to investigate the AT(1)R in vivo with positron-emission tomography (PET) and in vitro with quantitative autoradiography. AT(1)R PET measurements were performed with the radioligand [(11)C]KR31173 in 11 ...

Human breast cell carcinoma MCF-7 cells were found to bind 125I-labeled rat amylin (rAmylin) and the peptide amylin antagonist radioligand 125I-AC512 with high affinity. This high affinity binding possessed characteristics unique to the already defined high affinity binding site for amylin in the rat nucleus accumbens [Mol. Pharmacol. 44:493-497 (1993); J. Pharmacol. Exp. Ther. 270:779-787 (199...

In view of the therapeutic importance of dopamine D(3) and D(2) receptors, there remains considerable interest in novel ligands. Herein, we show that the tetrahydroisoquinoline 1H-indole-2-carboxylic acid {4-[2-(cyano-3,4-dihydro-1H-isoquinolin-2-yl)-ethyl]-cyclohexyl}-amide (SB269,652) behaves as an atypical, allosteric antagonist at D(3) and D(2) receptors. Accordingly, SB269,652 potently (lo...