Blood volume and erythropoiesis in the XXXX during spaceflight.

@entity1 @entity5301 @entity1503 @entity35 @entity68
A decreased @entity1503 ( @entity1503 ) and plasma volume (PV) have been consistently found in @entity1 after return from spaceflight. @entity35 flown on the Spacelab Life Sciences-1 mission were studied to assess changes in @entity1503 , PV, erythropoiesis, and @entity68 economy. The @entity1503 and PV increased in both ground control and flight animals as expected for growing @entity35 . However on landing day, both the @entity1503 and PV, when normalized for body mass, were significantly decreased in the spaceflight animals. During an 8-d postflight observation period, @entity68 incorporation into circulating red blood cells was diminished in the flight animals. During the first 4 d postflight, increases in reticulocyte counts were significantly smaller in the flight than the control animals. Fewer @entity5301 -responsive progenitor cells were recovered from the bone marrow of flight animals after landing than control rats. Serum @entity5301 ( @entity5301 ) levels were the same in both groups. Thus, @entity35 subjected to a 9-d spaceflight had less increase in @entity1503 than controls and diminished erythropoiesis during an 8-d post-spaceflight observation period. The @entity35 , like @entity1 , appears to require a smaller blood volume in microgravity.
