PLASMA RENIN ACTIVITY AND PLASMA ALDOSTERONE CONCENTRATIONS IN UNTREATED NIGERIANS WITH ESSENTIAL HYPERTENSION

Abstract

On the basis of existing information, we set out to test a hypothesis that the blood volume and more specifically total body sodium and sodium disposition in the body play a more important role in blood pressure regulation and the pathophysiology of hypertension than other regulatory mechanisms in the indigenous African'. To achieve our objective, ninety-eight newly diagnosed unmedicated hypertensives with adequate renal function were admitted to the study. Fifty-one (52% ) of the subjects were males while forty-seven (48% ) were females. Their ages ranged between 21 and 70 years. All grades of the disease were adequately represented with thirty (31% ) being mild, fifty (51%) moderate and eighteen (18.4% ) in the severe phase of the disease. Blood-pressure measurements and blood samples were obtained in the supine position in all the patients after adequate preparation. Plasma renin activity (PRA ) and plasma aldosterone concentrations were measured by specific radioimmunoassays. Contrary to what obtains elsewhere, seventy-six (77% ) of our patients were of the low renin status, twelve (12%) of whom had undetectable levels by our assay system. Eighteen (18.4%) had PRA levels in the medium range and five (5.1% ) in the high range. In a cohort, forty-two (43% ) of our ninety-eight patients, we estimated plasma aldosterone levels. The results obtained showed that the plasma aldosterone concentrations were significantly higher in hypertensives than in our normal controls ( I* < 0.01 ). There was lack of correlation between PRA or plasma aldosterone when compared to mean arterial pressure or serum Na +. These results are discussed in relation to the management of hypertension in our environment.