Trapping of labelled ligands in intact cells: a pitfall in binding studies

Biochem Pharmacol. 1983 Sep 1;32(17):2543-8. doi: 10.1016/0006-2952(83)90016-3.

Abstract

Binding on/in whole cells seems to be a more appropriate approach for studying receptor sites in physiological conditions. However, certain difficulties encountered throughout the characterization of [3H]spiperone binding in human lymphocytes led us to reconsider this problem. The IC50 values of [3H]spiperone binding to human lymphocytes did not correlate with those found in rat striatum; domperidone was inactive in lymphocytes whereas it is one of the most potent dopamine antagonists in rat striatal preparations in vitro. In contrast, chloroquine, a lysosomotropic drug, displaced [3H]spiperone at low concentration in intact lymphocytes but did not in the striatum. [3H]Spiperone binding was not displaceable in the membrane preparation of lymphocytes. Similar results were obtained with other intact cells, fibroblasts, hepatocytes and neuroblastoma cells using [3H]spiperone and other ligands, such as [3H]haloperidol, [3H]pyrilamine and [3H]ketanserin. Here again, displaceable binding was only present in intact cells but not in membrane fractions. Such a 'displaceable' binding was not related to receptor sites but may be regarded as non-specific binding which should correspond to a trapping phenomenon presumably in the lysosomes. Binding studies on intact cells need more caution than when performed on membrane preparations; indeed, permeation or trapping of ligands in the nanomolar range represents a serious drawback which, sometimes, can give the illusion of specific binding.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding, Competitive
  • Cell Line
  • Haloperidol / pharmacology
  • Humans
  • Kinetics
  • Lymphocytes / metabolism*
  • Mice
  • Neuroblastoma / metabolism
  • Receptors, Dopamine / drug effects
  • Receptors, Dopamine / metabolism*
  • Spiperone / metabolism
  • Tritium

Substances

  • Receptors, Dopamine
  • spiroperidol receptor
  • Tritium
  • Spiperone
  • Haloperidol