Michael Braukus
Headquarters, Washington, D.C.                                                     
October 8, 1993
(Phone:  202/358-1979)

Jane Hutchison
Ames Research Center, Mountain View, Calif.
(Phone:  415/604-9000)

RELEASE:  93-181

SHUTTLE RAT EXPERIMENT YIELDS UNEXPECTED RESULTS

     Unexpected results from a recent Space Shuttle experiment on 
rats some day may lead to the discovery of the genes that direct 
bone cells to produce more bone.

     Last April's third Physiological and Anatomical Rodent 
Experiment (PARE-3) studied changes in the activity of 
bone-forming cells after 9 days of space flight.  It also 
investigated whether these changes were reversed within 3 days of 
return to Earth.

     "We were totally surprised by some of the data from this 
flight experiment," said Dr. Emily Morey-Holton of NASA's Ames 
Research Center, Mountain View, Calif.

     Although she cautioned that much research remains to be done, 
Morey-Holton said the findings may accelerate the development of 
drugs to stimulate the production of new bone.  Such medications 
could be important not only for astronauts on long-duration space 
missions but also for people on Earth suffering from 
bone-weakening disorders. 

     At the end of the mission Morey-Holton and co-investigators 
Drs. Kim Westerlind and Russell Turner of the Mayo Clinic, 
Rochester, Minn., found a decrease in the production of certain 
chemical messages necessary for bone formation.  This was followed 
within 24 hours by a dramatic increase in production of these 
chemicals.  Levels again decreased within 72 hours after landing.  

     The 40 percent decrease in chemical messages was seen in 
cells on the outer surface of the lower leg bones (cortical bone).  
These messages direct bone-forming cells to produce proteins that 
are part of the process that results in formation of new bone.  
The investigators had expected this decrease since space flight is 
known to slow the rate of bone growth.

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     "The big surprise was an unexpected 300 percent increase in 
these proteins within 24 hours after return to Earth," 
Morey-Holton said.  "The response to reloading must have occurred 
almost immediately," she said.  Walking or movement against the 
force of gravity is known as a load.

     Morey-Holton said re-exposure to Earth's gravity may have 
caused the cells to overcompensate for the slowed bone growth 
during space flight.

     "This suggests that the best time to learn about the initial 
steps in bone formation may be within 24 hours after space 
flight," Morey-Holton said.  "The increase is probably large 
enough to allow scientists to establish a time course of events 
during the 24-hour period," she said.

     "It may be possible to tease out the genes involved in 
initiating cortical bone formation.  If you know what the actual 
trigger is, you should be able to use that particular message to 
actually stimulate bone formation," she said.  This, in turn, 
could lead to development of drug therapy.

     Because rats with unloaded hind limbs on Earth "showed 
virtually identical responses to the flight animals" on PARE-3, 
much additional research can be done in laboratories on the 
ground, she said.  "This should accelerate the research, because 
it eliminates the years of waiting often necessary for a flight 
opportunity on the Space Shuttle."

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