Red Cell Mystery

The experiments on the Air Force nurses shed no new light on a major medical mystery of the space age, which was described last week by Physician-Astronaut Joseph Kerwin: loss of 6% to 20% of the body's red blood cells in space and a delay in replacing them after returning to earth. "The plasma starts going immediately,"e; Kerwin told the American Academy of Pediatrics in Chicago, "and the red blood cells follow." Kerwin, who was responsible for medically monitoring his mates on Skylab 1, also found that loss of blood fluid--and muscle tissue--was so great that the thigh and calf actually shrank.

NASA doctors now know that the loss does not result from a destruction of red blood cells but from a shutdown of production facilities in the bone marrow. Upon returning to gravity, the body requires one to five weeks to start up production again. "Medically," says NASA Flight Surgeon Charles Ross, "that is one for the sleuths."

One hypothesis: the body is fooled in space. It feels good but, some doctors suggest, does not recognize its anemia. Another suspicion is that zero G alters the way the blood flows to the internal organs. This could result, for example, in reduced stimulation of the kidneys, which produce a hormone to trigger red blood cell manufacture.

Despite the mystery, NASA doctors seem generally elated by the human body's reaction to the long Skylab voyages. Loss of bone calcium was insignificant, work capacity was essentially unchanged, appetite remained high, and sleep came easily. Even the blood problem may turn out to be a simple matter of the body's adapting to a new condition. "Let's take the position of the devil's advocate," says Philip C. Johnson Jr., a Baylor College of Medicine consultant for NASA on blood studies. "We're not sure the drop of red blood cells might not be the best thing in space." All told, the doctors, and the space agency, are increasingly optimistic about man's--and woman's--ability to endure weightlessness, even for the years-long periods that will be required to reach other planets.

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