The Renin-Aldosterone System in Essential Hypertension

Ageing, Low Renin Hypertension, and the Relation between Renin Secretion and Aldosterone Secretion

Abstract

The responsiveness of the renin-aldosterone system to the stimuli of an intravenous injection of 60 mg of furosemide followed by a 2 hour walk was studied in 106 patients with essential hypertension.
In the patients, the mean plasma renin activity (PRA) was 1.47 ± 0.15 (S.E.M) ng/ml/hr, and the mean plasma aldosterone concentration (PAC) was 8.0 ± 1.6 (S.E.M) ng/dl in a recumbent position. In response to the combined stimuli of furosemide and walking, the PRA and PAC rose to 3.17 ± 0.29 (S.E.M) ng/ml/hr and 17.8 ± 1.2 (S.E.M) ng/dl, respectively. The mean PRA and PAC fell with increasing age, remarkably. so among those patients over 40 years in a recumbent position and also after the stimuli of furosemide and walking.
PRA was subnormal in 36.8 percent, normal in 53.8 percent and elevated in 9.4 percent of the subjects. In low renin hypertension, there was a tendency for the blood pressure to be higher and the age older than in other groups.
The mean values of PAC in low renin hypertension, normal renin hypertension and high renin hypertension in a recumbent position were 5.8 ± 0.6 (S.E.M) ng/dl, 8.4 ± 0.9 (S.E.M) ng/dl and 18.2 3.0 (S.E.M) ng/dl, respectively, and the difference was statistically significant between each. Therefore, it was suggested that the regulation of aldosterone secretion in essential hypertension might be governed mainly by the renin-angiotensin system, but a direct correlation was not found between PRA and PAC.
It was impossible to differentiate primary aldosteronism from low renin hypertension by means of PRA after the stimuli of furosemide and walking, but it could be differentiated after 3 days of sodium restriction, 3 days of administration of hydrochlorothiazide (7 5 mg/ day) and 3 hours of walking.