‘Dishrags’ After Week in Space : Rats Grow Weak in Zero-Gravity Study

Rats carried into space lost much of their muscle and bone strength during a week in orbit and returned to Earth limp “like dishrags,” a result that suggests that astronauts on long voyages may need protection from the wasting effects of zero gravity, a scientist says.

Richard Grindeland, a researcher at Ames Research Center in Mountain View, Calif., dissected 24 rats flown on the space shuttle last spring. He said Thursday that he found “very dramatic changes” in bone and muscle strength.

“Just after they came back, they were limp, like dishrags,” he said. “They had no muscle tone.”

The findings of the studies cannot be applied directly to humans, he said, but he added that the research does suggest that “we’ll really have to address this as a serious problem for the astronauts” before humans undertake a two-year or three-year round trip to Mars, for example.

Grindeland’s findings were based on a microscopic examination of bone and muscle from 24 rats flown on the space shuttle Challenger last May. Twelve of the rats were 2 months old, comparable in age to human adolescence, and the others were 3 months old, comparable to a human age of 25. A control group of rats of the same ages was kept on the ground.

After the mission, dissection showed that the space rats returned to Earth with smaller muscles and more brittle bones than the control group.

Grew Fatter but Weaker

Grindeland said the younger space rats lost up to 45% of their bone strength and as much as 40% of their muscle tissue while they were weightless in space.

“We saw similar changes--but they were much less dramatic--in the older rats,” he said. Loss of bone and muscle strength in the older rats was about 15%, he said.

Despite the debilitating effect of weightlessness, Grindeland said, all the orbiting rats adapted quickly and well to being in space. He said they did not lose their appetites (a common problem with human astronauts), and actually gained weight by about 25%.

As a result, he said, their loss of muscle and bone could be attributed only to weightlessness.