Document Detail


Ethnic differences in titratable acid excretion and bone mineralization.
MedLine Citation:
PMID:  11828240     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
PURPOSE: To test our hypothesis that differences in urinary calcium excretion among blacks and whites may be secondary to ethnic variations in acid (H(+)) metabolism and to prove that increases in titratable acid excretion would be found among individuals predisposed to the development of stress fractures. METHODS: We administered 8 g NH(4)Cl acutely to 11 black and 18 white healthy volunteers and measured urinary sodium, calcium, and acid excretions. We measured the Na(+)/H(+) antiporter activity using acid-loaded platelets as surrogate markers for this exchanger expressed in renal epithelial cells. We also compared differences in titratable acid excretion among a cohort of subjects with, and without, a history of stress fracture. RESULTS: NH(4)Cl-induced increases in titratable urinary acid correlated with changes in the renal excretion of calcium and sodium, and stimulated acid excretion correlated with basal acid loss. Despite comparable changes in plasma pH, whites, when compared to blacks, had much greater basal acid excretion and NH(4)Cl-induced acid excretion. Whites also had much greater baseline calcium excretion rates when compared to blacks. Following acid loading, whites continued to exhibit greater calcium excretion rates than blacks. Acid loading significantly decreased sodium excretion in whites but not in blacks. Blacks also had significantly attenuated Na(+)/H(+) exchange activity. In a cohort of resting, athletic students, we found enhanced basal H(+) and phosphate excretion among subjects who experienced stress fractures during their rigorous physical training when compared to those individuals who did not. CONCLUSION: Blacks may have a greater endogenous buffering capacity than whites, or the reported ethnic differences in sodium and calcium excretion rates between blacks and whites may be secondary to racial variations in renal H(+) excretion. We conclude that both ethnic differences in bone mineralization and bone integrity in athletes are mediated by heritable differences in titratable acid excretion.
Authors:
Henrikas Vaitkevicius; Richard Witt; Matthew Maasdam; Kevin Walters; Mark Gould; Steven Mackenzie; Stephen Farrow; Warren Lockette
Publication Detail:
Type:  Clinical Trial; Comparative Study; Controlled Clinical Trial; Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Medicine and science in sports and exercise     Volume:  34     ISSN:  0195-9131     ISO Abbreviation:  Med Sci Sports Exerc     Publication Date:  2002 Feb 
Date Detail:
Created Date:  2002-02-05     Completed Date:  2002-03-19     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  8005433     Medline TA:  Med Sci Sports Exerc     Country:  United States    
Other Details:
Languages:  eng     Pagination:  295-302     Citation Subset:  IM; S    
Affiliation:
Department of Medicine, Wayne State University School of Medicine, Detroit, MI, USA.
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MeSH Terms
Descriptor/Qualifier:
Acid-Base Equilibrium / physiology
Acids / blood,  urine*
African Continental Ancestry Group
Ammonium Chloride / administration & dosage
Biological Markers / urine
Calcification, Physiologic / physiology*
Calcium / urine*
European Continental Ancestry Group
Female
Fractures, Stress / ethnology*,  urine*
Humans
Male
Risk Factors
Sodium / urine*
Titrimetry
Grant Support
ID/Acronym/Agency:
1T35-HL07862/HL/NHLBI NIH HHS; 2R01-HL50849/HL/NHLBI NIH HHS
Chemical
Reg. No./Substance:
0/Acids; 0/Biological Markers; 12125-02-9/Ammonium Chloride; 7440-23-5/Sodium; 7440-70-2/Calcium

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