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Radioligand Binding Assays and Their Analysis

  • Janet J. MaguireEmail author
  • Rhoda E. Kuc
  • Anthony P. Davenport
Protocol
Part of the Methods in Molecular Biology book series (MIMB, volume 897)

Abstract

Radioligand binding is widely used to characterize receptors and determine their anatomical distribution, particularly the superfamily of seven transmembrane-spanning G protein-coupled receptors for both established transmitters such as endothelin-1 and an increasing number of orphan receptors recently paired with their cognate ligands. Three types of assay are described. In saturation experiments, tissue sections, cultured cells, or homogenates are incubated with an increasing concentration of a radiolabeled ligand, which can be a labeled analog of a naturally occurring transmitter, hormone, or synthetic drug. Analysis using iterative nonlinear curve-fitting programs, such as KELL, measures the affinity of the labeled ligand for a receptor (equilibrium dissociation constant, K D ), receptor density (B max), and Hill slope (nH). The affinity and selectivity of an unlabeled ligand to compete for the binding of a fixed concentration of a radiolabeled ligand to a receptor are determined using a competition binding assay. Kinetic assays measure the rate of association to or dissociation from a receptor from which a kinetic K D may be derived. Quantitative autoradiography and image analysis is a sensitive technique to detect low levels of radiolabeled ligands and determine the anatomical distribution of receptors in sections that retain the morphology of the tissue. The measurement of bound radioligand within discrete regions of autoradiographical images using ­computer-assisted image analysis is described.

Key words

Endothelin Apelin Ghrelin Motilin Neuropeptide W Urocortin II/III Urotensin II Equilibrium dissociation constant Bmax Hill slope Orphan receptor Quantitative autoradiography Image analysis Knockout mouse 

Notes

Acknowledgements

We thank the British Heart Foundation for support, grant numbers PG/09/050/27734 and RG/10/077/28300. Supported in part by the NIHR Cambridge Biomedical Research Centre.

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Copyright information

© Springer Science+Business Media, LLC 2012

Authors and Affiliations

  • Janet J. Maguire
    • 1
    Email author
  • Rhoda E. Kuc
    • 1
  • Anthony P. Davenport
    • 2
  1. 1.Clinical Pharmacology UnitAddenbrooke’s Centre for Clinical Investigation, University of CambridgeCambridgeUK
  2. 2.Clinical Pharmacology UnitUniversity of Cambridge, Addenbrooke’s Centre for Clinical InvestigationCambridgeUK

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