The Characterization of Low Renin Hypertension by Plasma Renin Activity and Plasma Aldosterone Concentration*

Low renin hypertension (LRH) is characterized by suppression of plasma reninactivity (PRA) in the absence of demonstrable hypersecretion of aldosterone. We have investigated the dynamics of PRA and plasma aldosterone (PA) in 10 normal subjects and 12 LRHpatients during 6 h of upright posture on both normal and low sodium diets. Angiotensin Irecovery experiments excluded an inhibitor of either angiotensin I generation or binding to specific antibody which could account for low PRA. LRH patients could be divided into two groups on the basis of their PRA response to sodium depletion and upright posture. Those patients whose PRA never exceeded 3.0 ng/ml/h were assigned to group I. Those whose PRA achieved this level at any time were assigned togroup II. Whereas PRA and PA levels were lower in both group I and group II patients thanin the normal subjects, the ratio ofPA to PRA was consistently higher in LRH group I patients than in normal subjects; this ratio was not significantly different from normal in grou...