Salt
retention hormone a greater factor in
African-American high blood
pressure
Newswise — Hypertension, or high blood
pressure, is 50 percent more prevalent in African Americans than in
Caucasians, and salt retention may be a potent contributor to this
high rate among African Americans. Aldosterone is an adrenal hormone
that promotes salt-retention by the kidney.
A new study by teams at the Medical
College of Wisconsin and the University of Montreal, Canada suggests
a significant link between higher levels of this hormone and high
blood pressure in African Americans.
The teams evaluated aldosterone levels
in relation to blood pressure in two distinct genetic populations:
Milwaukee-area African Americans, and a group of geographically and
genetically isolated French Canadians. Participants underwent
physical assessments, medical histories and 24-hour in-patient
monitoring of blood pressure and blood chemistry, including plasma
aldosterone, while supine and standing.
Over 1,000 members of Milwaukee’s
African American community have contributed to this ongoing research
at Froedtert Hospital, and more volunteers are needed.
The study was led by Theodore A. Kotchen,
M.D., associate dean for clinical research and professor of medicine
at the Medical College, and Pavel Hamet, M.D., Ph.D., at the
University of Montreal. Their abstract appears in the October 2004
issue of Hypertension, where the full manuscript has been accepted
for publication soon.
The researchers reported that blood
levels of aldosterone are higher in African Americans with high
blood pressure than in Caucasians, and that there is a highly
significant correlation between blood levels of aldosterone and
blood pressure in African Americans. In an earlier study, they also
found that elevated aldosterone is directly related to
over-development of the left ventricle of the heart in African
Americans with high blood pressure.
These observations may point the way to
drug therapies that would be particularly beneficial for African
Americans with high blood pressure, according to Dr. Kotchen.
“Specifically, we could predict that drugs that block the salt
retaining effect of aldosterone in the kidney would be particularly
effective agents to lower blood pressure in hypertensive African
Americans,” he says.
Ongoing, parallel research in
experimental models of hypertension by Allen W. Cowley Jr., Ph.D.,
chairman and professor of physiology at the Medical College, may
also help identify which patients with high blood pressure would
benefit most from these new therapies.
Dr. Cowley, director of the National
Specialized Center of Research on the Molecular Genetics of
Hypertension, is working to translate the genetic codes of
salt-sensitive rats developed in his laboratory to the human genome.
The human studies are supported by
grants from the National Institutes of Health (NIH), and conducted
by Medical College researchers in the NIH funded General Clinical
Research Center at Froedtert Hospital in Milwaukee, and by
University of Montreal Preventive and Community Genomic Medicine
Center researchers at Chicoutimi Hospital in the Saguenay-Lac St.
Jean region of Canada.
African Americans
may be eligible to participate in this research if they have high
blood pressure and are ages 18 to 55, or if they have normal blood
pressure and are ages 30 to 55. They cannot have diabetes, be
pregnant or morbidly obese.
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