Racial differences in potassium homeostasis in response to differences in dietary sodium in girls.
BACKGROUND
Racial differences in the renal disposition of potassium may be related to mechanisms for the greater susceptibility to hypertension in blacks than in whites.


OBJECTIVE
Our objective was to study the racial differences in the renin-angiotensin-aldosterone system and in potassium balance in black and white girls consuming a controlled diet that was low in potassium with 2 amounts of sodium intake (low compared with high).


METHODS
The studies reported here were performed in 40 black and 28 white girls, aged 11-15 y, under highly controlled metabolic conditions. The studies comprised 2 sessions of 20-d metabolic balance sessions, at 2 amounts of dietary sodium intake (58 and 170 mmol . L(-1) . d(-1)), in a crossover design and with a constant dietary potassium intake of 50 mmol . L(-1) . d(-1). Repeated-measures analysis of variance was used to test for racial differences in potassium output and retention by sodium intakes.


RESULTS
Thirty black and 20 white girls completed the study. Urinary potassium excretion was lower in blacks than in whites, regardless of sodium intake (P < 0.05), with no differences in fecal or sweat potassium excretion. Cumulative potassium retention was significantly higher in blacks while consuming the low sodium diet. Plasma aldosterone concentrations after upright posture were significantly lower in blacks than in whites but were similar when supine, as were urinary aldosterone excretion rates. On week 3, blood pressure, body weight, urinary volume, creatinine, and serum sodium and potassium were similar.


CONCLUSIONS
The well-known racial difference in urinary potassium excretion appears to be at least in part due to greater renal retention of potassium in black girls.
Palacios
Cristina
C
Graduate School of Public Health, University of Puerto Rico, San Juan, Puerto Rico. cristina.palacios@upr.edu
Wigertz
Karin
K
Martin
Berdine R
BR
Braun
Michelle
M
Pratt
J Howard
JH
Peacock
Munro
M
Weaver
Connie M
CM
D000293:Adolescent; D001741:Black or African American; D000450:Aldosterone / Q000378:metabolism; D000704:Analysis of Variance; D001794:Blood Pressure; D001835:Body Weight; D002648:Child; D003404:Creatinine / Q000652:urine; D018592:Cross-Over Studies; D004032:Diet; D004039:Diet, Sodium-Restricted; D005243:Feces / Q000737:chemistry; D005260:Female; D006706:Homeostasis; D006801:Humans; D006973:Hypertension / Q000378:metabolism*; D011187:Posture; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000097:blood; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage / Q000009:adverse effects*; D013542:Sweat / Q000737:chemistry; D044465:White People
D017673:Sodium Chloride, Dietary; D000450:Aldosterone; D012964:Sodium; D003404:Creatinine; D011188:Potassium