such as "Introduction", "Conclusion"..etc
May 13, 2009 — When stress increases blood
pressure, a natural mechanism designed to bring it down by excreting
more salt in the urine doesn't work well in about one-third of healthy,
African-American adolescents, researchers report.
They hope the finding, presented May 8 at the American Society of
Hypertension 24th Annual Scientific Program in San Francisco, will lead
to early identification of youth at risk of becoming hypertensive
"The way it's supposed to work is the higher your blood pressure
goes, the system is supposed to be suppressed so you urinate out more
sodium and the blood pressure goes down in response," says Dr. Matthew
Diamond, nephrology fellow in the Medical College of Georgia School of
Medicine. Dr. Diamond, who is presenting the findings, is a finalist
for the society's 2009 Young Investigator-in-Training abstract
The renin-angiotensin-aldosterone system helps regulate blood
pressure, prompting the kidneys to hold onto more salt – and fluid – if
it's too low and to get rid of salt when it's high.
But when MCG researchers looked at the system's activity by
measuring levels of the hormones it uses to help regulate sodium
excretion, the system – which worked essentially perfectly in healthy
white adolescents – appeared dysfunctional in a significant number of
the black adolescents.
The study involved168 15-18-year-olds with normal pressures who had
been on sodium- and potassium- controlled diets for two weeks.
Researchers took blood pressure, urine and blood samples as
participants rested for two hours, played video games intended to
stimulate environmental stress, then recovered for two hours at MCG's
Georgia Prevention Institute.
"For reasons we don't understand, the black kids have improper
suppression of this renin-angiotensin-aldosterone system," Dr. Diamond
To make sure the "fight-or-flight" mechanism designed to raise blood
pressure to escape a tight spot was not to blame for holding onto
sodium, the researchers measured heart rates but could find no
relationship. Fat, which produces aldosterone, a hormone that can
increase sodium retention, also was ruled out because participants were
"There is nothing we know about that is explaining what we are
seeing yet we have some pathology here that could potentially explain
difficult hypertension in kids," he says.
One of his next steps is screen participants for a genetic mutation
that has been linked to hypertensive kidney disease to see if that's a
factor that can be used to help identify those at risk for hypertension
and kidney disease.
Study contributors include Dr. John J. White, MCG nephrologist, and
Dr. Gregory Harshfield, director of the Georgia Prevention Institute.
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