[Renal functioning and human body liquids during 5-day dry immersion]

Renal function and body composition, including liquids, were investigated in 14 essentially healthy male subjects during simulation of some spaceflight effects by 5-d dry immersion (DI). Noninvasive measurement of water spaces of organism was performed with the methods of bio-impedance analysis (BIA). Increase of renal excretion of liquids and appearance of negative water balance were observed. BIA revealed reductions of total body and extracellular liquids and a decrease of circulating plasma volume. This means, that DI induced hypohydration of organism. In the post-DI period, the hydration status regained its baseline level fairly soon. Lean body mass slightly decreased; adipose mass, on the contrary, exceeded baseline values. Moreover, the experiment evidenced technical impossibility to obtain valid impedansimetry data in DI.