Unexpected renal responses in space.

Lancet · 2000

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Abstract

Urine output in astronauts following ingestion of an oral water load was low in space on the Russian space station Mir and less than during simulation by 6 degrees head-down bed rest. This surprising observation shows that the effects of gravity and weightlessness on fluid volume regulation are not well understood and that the head-down bed-rest model does not simulate the effects of weightlessness on renal water handling.