Highlighted below are preliminary findings of SLS-1 experiments, which involved interrelated studies of human and animal adaptation to space. Consistent with findings from similar experiments, white blood cell responsiveness, which helps the body fight infections, decreased. Preliminary results from the blood volume study show that within the first 24 hours of space flight, the volume of blood decreases by more than 10 percent in astronauts. The redistribution of blood that occurs during spaceflight causes the blood volume to be less than optimal upon return to Earth. Readaptation results from an increase in plasma volume over several hours and red blood cell mass over a few days.
Astronauts have a reduced red blood cell mass after exposure to space.
Various hypotheses have been made to account for this reduction, but they remain unproven. For the first time the kidney's role in compensating for weightlessness was studied. Preliminary analysis shows very early changes occur in body compartment analysis and hormone results. Scientists say the importance of the renal involvement in blood volume and pressure control must now be considered in the assessment of the health status of spaceflight crews. Direct and continuous measurement of central venous pressure using a cathetor produced unexpected results that suggested that much of the cardiovascular adaptation to space occurs on the launch pad and during launch.