Michael Braukus
Headquarters, Washington, DC         November 14, 1996
(Phone:  202/358-1979)

Ann Hutchison
Ames Research Center, Mountain View, CA
(Phone:  415/604-4968)


RELEASE:  96-237

 SHUTTLE EXPERIMENT TO STUDY HIGH BLOOD PRESSURE

     Rats with high blood pressure flying on the next Space 
Shuttle mission, STS-80, may help scientists better 
understand how calcium helps maintain human health.
 
      An experiment by Drs. David McCarron and Daniel Hatton, 
hypertension specialists from the Oregon Health Sciences 
University in Portland, will examine calcium's role in blood 
pressure regulation.  Calcium has long been recognized as a 
critical mineral in the normal development and function of 
bone and muscle.
 
     "A large body of evidence indicates that problems in the 
way the body processes calcium also can lead to hypertension, 
or high blood pressure," Hatton said.  "This flight 
experiment will help us clarify the role calcium levels play 
in this condition." 

     Hypertension affects over 50 million Americans and 
contributes to heart attack, stroke and kidney disease.  It 
costs the nation's health care system billions of dollars 
annually, McCarron said.  Dietary calcium appears to have its 
greatest effect on blood pressure when calcium demands on the 
body are highest.

     McCarron and Hatton were among the first to propose that 
adequate dietary calcium is essential for normal 
cardiovascular function.  They have tested their hypothesis 
in studies with humans and rats, with both normal and 
elevated blood pressures.  The model for their studies is 
known as the Spontaneously Hypertensive Rat, which is 
genetically predisposed to calcium-related high blood 
pressure.  It is thought that space flight causes a decrease 
in intestinal absorption of dietary calcium.  Study of this 
animal model will enable the investigators to determine how 
the changes occurring in dietary calcium absorption affect 
blood pressure control.

     NASA is interested in how changes in gravity affect the 
metabolism of calcium, since loss of bone mass during space 
flight may cause osteoporosis in astronauts earlier than in 
people on Earth.  Because bones, which support the body 
against gravity's pull, are not stressed in space, they shed 
calcium into the blood and then out of the body.  The process 
begins immediately upon leaving Earth's gravity and appears 
to continue unabated for the entire time in microgravity.  
After just a few months in space, an astronaut's mass in 
supporting bones will drop 8 -10 times faster than 
corresponding loss of bone mass for aging people on Earth.

     This is NASA's first study on calcium and blood pressure 
in space.  Known as NIH-R4, this experiment is the fourth in 
a series of life sciences studies jointly sponsored by NASA 
and the National Institutes of Health (NIH).  The NIH-R 
experiments use rodents to study various biological aspects 
of space flight.  NASA's Ames Research Center, Mountain View, 
CA, is the experiment developer. 

     This flight experiment will include two groups of rats, 
one on a high-calcium diet, the other on a diet low in 
calcium.  After the flight, scientists will conduct tests on 
tissues from the rats to find out how the different calcium 
intakes affected blood pressure and cardiovascular 
functioning in the microgravity environment.

     "This research offers hope to the tens of millions of 
people suffering from calcium-related conditions such as 
osteoporosis and hypertension," McCarron said.

     For more information about the NIH-R4 study, see the 
home page at URL 
http://weboflife.arc.nasa.gov/EXPLORATIONS/MISSIONS/nihr4.htm
l.

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