Varying Influences of Aldosterone on the Plasma Potassium Concentration in Blacks and Whites.
BACKGROUND
Aldosterone acts to restrain the extracellular potassium (K+) concentration. Blacks have on average lower plasma aldosterone concentrations (PACs) than Whites. Whether this ethnic difference is associated with similar changes in the concentration of K+ is unclear.


METHODS
Subjects were Blacks and Whites from an observational study of blood pressure regulation. PAC was known to be significantly lower in Blacks than Whites. We sought to test the hypothesis that the concentration of K+ remains constant despite variability in PAC. Initial enrollment took place in childhood in 1986. Some of the original enrollees were studied again in adulthood: 160 healthy Blacks and 271 healthy Whites (ages 5 to 39 years; all were studied as children and as adults).


RESULTS
Plasma renin activity [a biomarker of angiotensin II and, more proximally, extracellular fluid volume (ECFV)] and PAC were lower in Blacks (P < 0.0354 and P < 0.001, respectively, for all ages). At the same time no ethnic difference in levels of K+ was observed regardless of age. Plasma K+ concentration and PAC associated differently based on ethnicity: PAC increased in Blacks by 1.5-2.0 and in Whites by 2.3-3.0 ng/dl per mmol/l increase in K+ (P < 0.001).


CONCLUSIONS
Lower aldosterone levels in Blacks did not translate into higher K+ concentrations. We speculate that reaching the right concentration of K+ was an endpoint of aldosterone production in the presence of varying levels of ECFV and angiotensin II.
Department of Biostatistics, Indiana University Center for Aging Research, Regenstrief Institute, Indianapolis, Indiana, USA.|Indiana University Center for Aging Research, Regenstrief Institute, Indianapolis, Indiana, USA.
Wanzhu
W
Tu
Department of Biostatistics, Indiana University Center for Aging Research, Regenstrief Institute, Indianapolis, Indiana, USA.
George J
GJ
Eckert
Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.
Brian S
BS
Decker
Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.|Roudebush V.A. Medical Center, Indianapolis, Indiana, USA.
John
J
Howard Pratt
D000293:Adolescent; D000328:Adult; D001741:Black or African American; D000367:Age Factors; D000450:Aldosterone / Q000097:blood*; D001794:Blood Pressure; D002648:Child; D002675:Child, Preschool; D005260:Female; D054624:Health Status Disparities; D006801:Humans; D007196:Indiana; D008297:Male; D011188:Potassium / Q000097:blood* / Q000652:urine; D011446:Prospective Studies; D012083:Renin / Q000097:blood; D012084:Renin-Angiotensin System; D012964:Sodium / Q000652:urine; D014882:Water-Electrolyte Balance; D044465:White People; D055815:Young Adult
D000450:Aldosterone; D012964:Sodium; D012083:Renin; D011188:Potassium
aldosterone; angiotensin II; blood pressure; ethnicity; extracellular fluid volume; hypertension; potassium.