Characterization of [³H]Ouabain Binding Sites in Human Brain, Platelet, and Erythrocyte

[³H]Ouabain binding was investigated in membranes prepared from human brain, erythrocyte, and platelet. Scatchard analysis of [³H]ouabain binding to human hypothalamic membranes revealed a single class of noninteracting binding sites with an apparent affinity constant (K_D) of 21 nM. Though the number of [³H]ouabain binding sites was lower in human platelets than in erythrocytes, both tissues exhibited a single class of high‐affinity binding sites with an apparent K_D similar to that found in human brain. Specific [³H]ouabain binding in basal ganglia tissue from patients with Huntington's disease was more than 50% lower than in tissue from age‐ and sex‐matched controls. These results, along with previous findings in rat brain, suggest that high‐affinity [³H]ouabain binding labels the neuronal form of Na,K‐ATPase in human brain, and may prove useful in quantitating this enzyme in postmortem brain samples.