Muscle, Bone Strength Loss May Apply to Humans : Weightlessness Yielded ‘Dishrag’ Rats
Space rats that spent seven days in orbit suffered massive losses of muscle and bone strength, suggesting that astronauts on long voyages must be protected from the debilitating effects of zero gravity, a scientist says.
“There are changes, and very dramatic changes, in the bones during space flight,” said Richard Grindeland, a researcher at the Ames Research Center in California. “And what happens, happens very, very quickly.”
The same is true of muscles, he said Thursday. “Just after they came back, (the rats) were limp, like dishrags. They had no muscle tone.”
The results of the rat studies cannot be directly applied to the human body’s reaction to spaceflight, but they do suggest that more experiments should be conducted before astronauts attempt the two to three years of weightlessness that would be required for a round trip to Mars, Grindeland said.
Twenty-four rats accompanied the crew of Challenger last May in an experiment directed by Grindeland, a physiologist. Twelve of the rats were 2 months old, comparable to human adolescence; the others were 3 months old, comparable to about 25 human years.
A control group of rats of the same ages were kept on the ground.
The space rats were killed after the mission and samples of muscle and bone were examined microscopically and compared with those of the control rats, which also were killed.
The young space rats experienced a bone strength loss of up to 45% and a muscle tissue loss of up to 40%, Grindeland said. “We saw similar changes, but they were much less dramatic, in the older rats,” which suffered bone and muscle strength losses of about 15%, he said.
The change in the bones, he said, was not in the loss of calcium or minerals, but in the bending and breaking strength, meaning that the bones were much less able to withstand stress.
Despite the loss of bone and muscle strength, all the rats seemed to adapt quickly and well to spaceflight, he said. They did not experience a loss of appetite, which is common in human astronauts.
