Characterization of "high-affinity" [3H]ouabain binding in the rat central nervous system.
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.
Hauger
R
R
Luu
H M
HM
Meyer
D K
DK
Goodwin
F K
FK
Paul
S M
SM
D000818:Animals; D001923:Brain Chemistry; D002301:Cardiac Glycosides / Q000494:pharmacology; D003342:Corpus Striatum / Q000378:metabolism; D066298:In Vitro Techniques; D007608:Kainic Acid / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D009711:Nucleotides / Q000494:pharmacology; D010042:Ouabain / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D011955:Receptors, Drug / Q000032:analysis*; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis; D014316:Tritium
D002301:Cardiac Glycosides; D009711:Nucleotides; D011955:Receptors, Drug; C028996:cardiac glycoside receptors; D014316:Tritium; D010042:Ouabain; D011189:Potassium Chloride; D000254:Sodium-Potassium-Exchanging ATPase; D007608:Kainic Acid