[Aldosterone excretion and plasma renin activity in patients with essential hypertension and with primary aldosteronism (author's transl)]

Cardiovascular and adrenal sensitivity to angiotensin II in essential hypertension

Regulation of aldosterone secretion by sodium chloride is impaired in a group of essential hypertensives: high-salt diet fails to suppress aldosterone in these patients despite low renin values. The mechanism of this impaired regulation of aldosterone has not been clarified so far. We tested the sensitivity of aldosterone secretion and blood pressure to A II in 20 normotensive controls (aged 20-60, MAP 92 +/- 3 mm Hg), in ten normotensives with one or two parents with hypertension, and in 21 patients with essential hypertension (aged 17-65, MAP 119 +/- 4 mm Hg). After a period of 6 days on high-salt intake (300-320 mEq Na+/day), A II (0.1, 0.5, 1.0 and 2.0 ng/kg/min) was infused, each concentration for 30 min. According to aldosterone excretion during sodium loading, patients were divided into group A with complete suppression (n = 12, aldosterone excretion 3.6 +/- 0.4 microgram/day) and in group B with insufficient suppression (n = 9, aldosterone excretion 15.5 +/- 2.3 micrograms/day). Despite similarly low plasma renins, rise of serum aldosterone levels during A II infusion was significantly higher in group B patients than in group A patients and normotensive controls. Rise in mean arterial blood pressure, however, brought about by graded A II infusion was similar in both groups of hypertensives and in normotensive controls. The results demonstrate an increased adrenal sensitivity to A II in a subgroup of essential hypertensives only. A similar adrenal hypersensitivity to A II found by others in patients with hyperaldosteronism due to adrenal hyperplasia supports the hypothesis that the same mechanism underlies both disorders.

Characterization of a group of essential hypertensives with impaired regulation of aldosterone

The pattern of aldosterone excretion during high sodium intake in 100 patients with essential hypertension allowed the differentiation of two groups: in the majority of patients (group A, n = 64) aldosterone excretion was suppressed below 6 micrograms/day similar to the normotensive control group. In a second group (group B, n = 36), aldosterone remained above the control range despite forced sodium loading. In group B, serum potassium was significantly lower than in patients of group A (3.81 +/- 0.44 meq/l vs. 4.26 +/- 0.57 meq/l, p less than 0.001). The blood pressure lowering effect of spironolactone (200 mg/d) was more pronounced among patients in group B. Plasma renin values tended to be lower in group B compared to patients with suppressed aldosterone. Infusion of Angiotensin II (0.1 - 2 micrograms/kg/min) led to a similar relative rise of plasma aldosterone levels in both groups despite higher baseline values in group B. The exact mechanism of the impaired regulation of aldosterone in a subgroup of patients with essential hypertension remains to be elucidated.