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Gastrointestinal and renal excretion of potassium in African–Americans and White Americans

Rosa, Robert M.a; De Jesus, Ernesta; Sperling, Kevina; Suh, Anniea; Gmurczyk, Aleksandraa; Myrie, Kevin A.a; Rosner, Karola; Lerma, Edgara; Yu, Williama; Breuer, Richardc; Young, James B.b

doi: 10.1097/HJH.0b013e32835a27b3
ORIGINAL PAPERS: Kidney

Objective: Several studies have confirmed the remarkable observation that cumulative urinary potassium (K+) excretion is less in African–Americans than White Americans even when identical amounts of potassium are provided in the diet. This study was designed to examine whether this decrease in urinary potassium could be compensatory to an increase in gastrointestinal excretion of potassium in African–Americans.

Methods: Twenty-three young, healthy, normotensive participants of both sexes and races were placed on a fixed diet of 100 mEq per day of K+ and 180 mEq per day of sodium (Na+) for 9 days. All urine and stool were collected daily and analyzed for electrolytes. Blood was obtained for determination of electrolytes, blood urea nitrogen (BUN), creatinine, glucose, insulin, renin, and aldosterone at the beginning and at the end of the study period.

Results: Cumulative urinary excretion of K+ was significantly less in African–Americans (609 ± 31 mEq) compared with White Americans (713 ± 22 mEq, P = 0.015). There was no significant racial difference, however, in the cumulative gastrointestinal excretion of K+ (105 ± 11 versus 95 ± 9 mEq, P = 0.28) in African–Americans versus White Americans, respectively.

Conclusion: The racial difference in urinary K+ handling manifested by decreased excretion of K+ in African–Americans cannot be attributed to an increase in net gastrointestinal excretion of this cation.

aDivisions of Nephrology/Hypertension, Department of Medicine

bDivisions of Endocrinology, Metabolism and Molecular Medicine

cDivision of Gastroenterology, The Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA

Correspondence to Robert M. Rosa, MD, Feinberg School of Medicine, Arthur J. Rubloff Building, 420 East Superior St., Chicago, IL 60611-3008, USA. Tel: +1 312 908 5502; fax: +1 312 503 7654; e-mail: rrosa@northwestern.edu

Abbreviations: K+, Potassium, Na+, Sodium

Received 26 March, 2012

Revised 27 July, 2012

Accepted 6 September, 2012

© 2012 Lippincott Williams & Wilkins, Inc.