Plasma renin activity and plasma aldosterone concentrations in untreated Nigerians with essential hypertension.

On the basis of existing information we set out to test an 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 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 (P less than 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.