Evidence for Increased Levels of a Circulating Ouabainlike Factor in Essential Hypertension

SUMMARY The effect of plasma from normotensive and hypertensive subjects on the binding of [3H]ouabain on human erythrocytes was investigated. The binding of [3H]ouabain on human erythro-cytes was saturable and highly specific; linear Scatchard plots indicated the presence of a single type of binding site. Human plasma decreased the binding of ['HJouabain on its receptor to a greater extent than could be accounted for by the plasma potassium concentration. The level of this circulating ouabainlike factor (or factors) was quantitated using a radioreceptor assay. Plasma from 22 hyperten-sive subjects (systolic blood pressure> 160 mm Hg or diastolic blood pressure>90 mm Hg) displayed higher levels than that from 24 normotensive subjects; furthermore there was a positive and signifi-cant correlation (r = 0.42, n — 46, p < 0.004) between the ouabainlike content and the individual subject's systolic blood pressure. The receptor assay described is relatively simple and should be useful for further work on the nature and clinical importance of the endogenous ouabainlike factor. (Hypertension 8: 433-437, 1986) KEY WORDS • hypertension • Na+-K+ pump inhibitor radioreceptor assay ouabainlike facto