Characterization of “High‐Affinity”[3H]Ouabain Binding in the Rat Central Nervous System

R. Hauger, H. M.D. Luu, D. K. Meyer, F. K. Goodwin, S. M. Paul

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Abstract

The characteristics of [3H]ouabain binding were examined in various areas of rat brain. In the striatum, Scatchard analysis revealed a single class of “high‐affinity” binding sites with an apparent binding affinity (KD) of 10.4 ± 0.9 nM and an estimated binding capacity (Bmax) of 7.6 ± 1.9 pmol/mg protein. Similar monophasic Scatchard plots were found in the brainstem, cerebellum, hypothalamus, and frontal cerebral cortex. [3H]Ouabain binding to rat brain was sodium‐ and ATP‐dependent and strongly inhibited by potassium. Proscillariden A was the most potent cardiac glycoside tested in inhibiting specific [3H]ouabain binding to brain membranes, and the rank order of inhibitory potencies for a series of cardiac glycosides was similar to that previously reported for inhibition of heart Na,K‐ATPase. To assess whether the high‐affinity binding sites for [3H]ouabain were localized to neuronal or nonneuronal membranes, the effect of discrete kainic acid lesions on striatal [3H]ouabain binding was examined. Kainic acid lesions of the striatum reduced [3H]ouabain binding to striatal homogenates by 79.6 ± 1.6%. This suggests that the “high‐affinity”[3H]ouabain binding sites measured in our experiments are localized to neuronal elements. Thus, the high‐affinity binding of [3H]ouabain to brain membranes may selectively label a neuronal form or conformation of Na,K‐ATPase.

Original languageEnglish
Pages (from-to)1709-1715
Number of pages7
JournalJournal of Neurochemistry
Volume44
Issue number6
DOIs
StatePublished - Jun 1985

Keywords

  • Brain
  • Kainic acid
  • Na,K‐ATPase
  • “High‐affinity”[H]ouabain binding

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