Pharmaceutisch Weekblad

, Volume 6, Issue 6, pp 241–244 | Cite as

Does the tissue concentration in receptor binding studies change the affinity of the labelled ligand?

  • K. Ensing
  • R. A. De Zeeuw
Short Communications


When the tissue concentration in a radioreceptor assay for anticholinergic drugs was varied in order to obtain optimum conditions, and the receptor concentration Ct and the equilibrium dissociation constant KD were determined by Scatchard analysis, the KD increased with increasing tissue concentrations. This phenomenon was considered as an artefact caused by non-specific binding of the labelled ligand to constituents of the receptor preparation which were not completely retained on the glassfibre filters used for the separation of bound and free fraction of radio-labelled ligand. The increase in KD in these experiments could be described with a mathematical model of the binding experiments.


Receptor Binding Tissue Concentration Binding Study Binding Experiment Free Fraction 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Ensing K, Kluivingh F, Gerding TK, De Zeeuw RA. Development of a sensitive radioreceptor assay for oxyphenonium in plasma and urine. J Pharm Pharmacol 1984;3:235–9.Google Scholar
  2. 2.
    Ensing K, De Zeeuw RA. Radioreceptor assay of anticholinergic drugs in biological fluids. In: Reid E, ed. Drug determination in therapeutic and forensic contexts. London: Plenum Press, 1984:287–96.Google Scholar
  3. 3.
    Scatchard G. The attraction of proteins for small molecules. Ann NY Acad Sci 1991;51:660–72.Google Scholar
  4. 4.
    Ensing K, De Zeeuw RA. Radioreceptor assay — a tool for the bioanalysis of drugs. Trends Anal Chem 1984;3:102–6.CrossRefGoogle Scholar
  5. 5.
    Mackerer CR, Kochman RL, Bierschenk BA, Bremner SS. The binding of (3H)-diazepam to rat brain homogenates. J Pharmacol Exp Ther 1978;206:405–13.PubMedGoogle Scholar
  6. 6.
    Möhler H, Okada T. Properties of (3H)-diazepam binding to benzodiazepine receptors in rat cerebral cortex. Life Sci 1977;20:2101–10.CrossRefPubMedGoogle Scholar
  7. 7.
    Lazareno S, Nahorski SR. Errors in KD estimates related to tissue concentration in ligand binding assays using filtration. Br J Pharmacol 1982;77:571.Google Scholar

Copyright information

© Royal Dutch Association for Advancement of Pharmacy 1984

Authors and Affiliations

  • K. Ensing
    • 1
  • R. A. De Zeeuw
    • 1
  1. 1.Department of ToxicologyState University of GroningenAW GroningenThe Netherlands

Personalised recommendations