Protein kinetics during and after long-duration spaceflight on MIR

1 Department of Surgery, School of Osteopathic Medicine, University of Medicine and Dentistry of New Jersey, Stratford, New Jersey 08084; and 2 Institute for Biomedical Problems, Moscow 123007, Russia Human spaceflight is associated with a loss of body protein. Bed rest studies suggest that the reduction in the whole body protein synthesis (PS) rate should be ~15%. The objectives of this experiment were to test two hypotheses on astronauts and cosmonauts during long-duration (>3 mo) flights on MIR: that 1 ) the whole body PS rate will be reduced and 2 ) dietary intake and the PS rate should be increased postflight because protein accretion is occurring. The 15 N glycine method was used for measuring whole body PS rate before, during, and after long-duration spaceflight on the Russian space station MIR. Dietary intake was measured together with the protein kinetics. Results show that subjects lost weight during flight (4.64 ± 1.0 kg, P