Using low doses of bromine and radioisotopes, the following parameters were measured: total body water, intracellular fluid, extracellular fluid, plasma volume, interstitial fluid, blood volume, and red blood mass. Preflight, measurements were taken in 11 monkeys, 2 of which later flew on the 14 day biosatellite mission. Measurements were repeated in the two flight monkeys 36 hours after recovery. Although during this time the animals were provided with fluids ad libitum, this is not believed to be a problem, since previous studies in humans have shown that a dehydrated body is unable to compensate rapidly for fluid loss, even when fluids are consumed in large quantities. Since approximately 100 days separated the pre- and post-flight measurements, growth control measurements were made in 4 vivarium animals. The parameters were also measured in R+45 restraint control animals.

Results:

Both flight monkeys showed a decrease in all parameters compared to the preflight level. This replicates the findings from previous primate flights. During the 100 days, the fluid volumes of the growing animals increased. However, the parameters expressed as a percent of body mass decreased, as is seen when both lean and adipose body mass increase. ECF increased to a greater extent than ICF, suggesting that the animals' metabolic activity decreased as they grew. Similar age-related changes can be assumed to have taken place in the flight animals. Therefore, when compared to the control data, flight data was found to be less significant. ECF decreased to a greater degree (11% and 8% in the two monkeys, due to a 13% and 12% decline in interstitial fluid) than ICF, a change that could be unfavorable for the support of cell structures. These adaptive changes are inadequate at 1G, leading to diminished motor activity upon return to earth. After recovery, the measured parameters returned to normal levels. Similar but less significant trends were observed in the R+45 restraint control animals.