Characterization of ouabain receptor in neuronal tissue: evidence for endogenous ouabain-like compound

This study shows that [3H]ouabain binds specifically to a single, saturable binding site located on rat brain membranes with an affinity constant of 6.21 X 10(-8) M. As expected from studies on the mechanics of the Na+,K+-ATPase, sodium increased while potassium and lithium decreased ouabain binding. The occupation of other neurotransmitter receptors did not affect [3H]ouabain binding. Based on its ability to compete with [3H]ouabain binding and to inhibit Na+,K+-ATPase, it is suggested that rat brain extract contains an endogenous ouabain-like compound. The results are discussed with respect to the possibility that the ouabain receptor is a physiological regulatory site of the Na+,K+-ATPase activity.