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Effect of administered potassium on the renin-aldosterone axis in young blacks compared with whites
J H Pratt1, A K Manatunga, M P Hanna
1Department of Medicine, Indiana University School of Medicine and the Veterans Administration Medical Center, Indianapolis, USA.
Insights
Potassium supplementation equally increased aldosterone production in Black and White children. Lower potassium intake may contribute to the suppressed renin-aldosterone system observed in Black individuals.
Area of Science:
- Endocrinology
- Renal Physiology
- Racial Health Disparities
Background:
- Previous observations indicated lower aldosterone excretion and plasma concentrations in Black children compared to White children.
- The underlying cause for this difference remained unclear, with possibilities including lower potassium intake or renin-angiotensin system suppression in Black individuals.
Purpose of the Study:
- To investigate racial differences in aldosterone secretion in response to potassium supplementation.
- To test the hypothesis that potassium's effect on aldosterone differs between Black and White children.
Main Methods:
- A randomized, double-blind, placebo-controlled crossover study was conducted with 12 Black and 12 White children.
- Participants received either placebo or 40 mmol/day potassium chloride for 7 days, with measurements of plasma renin activity (PRA), plasma aldosterone concentration, and urinary aldosterone excretion.
- Blood pressure was monitored for 24 hours.
Main Results:
- Potassium supplementation significantly increased plasma aldosterone concentration and urinary aldosterone excretion in both Black and White children, with no significant racial difference in response.
- Plasma renin activity (PRA) was significantly lower in Black children compared to White children.
- Potassium treatment tended to increase lower PRA levels, and blood pressure remained stable in both groups.
Conclusions:
- Aldosterone production increased similarly in both racial groups following potassium supplementation.
- The findings suggest that lower potassium intake may partially explain the suppressed renin-aldosterone system in Black individuals.
- Potassium supplementation appears to enhance PRA levels, particularly in those with initially lower levels.
Background:
We had observed previously that the aldosterone excretion rate and plasma aldosterone concentration were lower for black children than they were for white children. We did not know whether this was secondary to a lower intake of potassium or to suppression of the renin-angiotensin system in blacks.
Objective:
To test the hypothesis that the secretion of aldosterone in response to potassium would be different in blacks than in a control group of whites.
Design:
Black and white subjects were selected on the basis of their having aldosterone excretion rates that were in the lowest quartile for the entire original cohort. Since the blacks typically had lower aldosterone excretion rates than did the whites, the black participants were represented primarily by those with average rates of aldosterone production among blacks, whereas the whites were represented by those with the lowest aldosterone production rates among whites. The protocol consisted of a placebo-controlled, randomized cross-over study design.
Methods:
Twelve blacks and 12 whites, aged 14.1 +/- 1.6 (mean +/- SD) and 15.4 +/- 2.1 years, respectively, were allocated randomly to double-blind treatment either with placebo or with 40 mmol/day potassium chloride for 7 days and then the alternate treatment Measurements of the plasma renin activity (PRA), plasma aldosterone concentration, and urinary aldosterone excretion were performed in an inpatient research unit at the end of the treatment. The blood pressure was monitored for 24 h.
Results:
Treatment with potassium increased the plasma aldosterone concentration (P = 0.0006) and the urinary excretion of aldosterone (P = 0.0002) significantly both for blacks and for whites. There was no significant racial difference in the response to potassium. The PRA was overall 1.605-fold lower in the blacks than it was in the whites (P = 0.0124). The lowest PRA levels, such as those in the blacks when they were supine, tended to be increased with the potassium treatment. The blood pressure did not change significantly with the potassium supplement for either racial group.
Conclusions:
After we had supplemented the intake of potassium, aldosterone production increased in the blacks and in the control group of whites to the same extent The potassium treatment appeared to increase lower PRA levels. A lower intake of potassium could at least partially account for the suppression of the renin-aldosterone system in blacks.