PRINCIPAL INVESTIGATOR ( S ) : Philip C. Johnson, Theda B. Driscoll, and Adrian 



D. LeBlanc 



EXPERIMENT TITLE/NUMB ER: Blood Volume Changes, Ml 13 



PROGRAM/MISSION : Skylab 2, 3, 4 



CLASSIFICATION : Human 



DISCIPLINE(S) : Hematology 



OBJECTIVES : To determine the effects of weightlessness on the blood plasma 

 volume and the red blood cell population, with particular attention paid 

 to changes in the total mass of red cells, red cell destruction, red cell life 

 span, and red cell production rate. 



PROTOCOL : The red cell mass determination was obtained by averaging the red 

 cell radioactivity of a 30- and 31- minute blood sample. Thirty days prior to 

 launch, 50 WCi C-glycine were injected intravenously for a red cell life 

 span study. At recovery, 2 Ci of Fe citrate were injected for calculation 

 of iron turnover using the 30-, 31- minute samples and a sample drawn 2 to 3 

 hours later. Reticulocyte-|Counts were obtained weekly preflight and 

 postf light. Activity of Cr red cells was measured to estimate red cell 



chromium half life. Plasma volume was measured by injecting 2uCi I human 

 serum albmium each time the red cell mass was determined. 



EQUIPMENT : Inflight blood collection system. 



RESULTS : The mean value of red cell mass of crewmembers showed a decrease of 

 5-12$ through the first weeks inflight. The mean ratio of milliliters/kilogram 

 body weight also decreased. Red cell mass regeneration did not occur until 

 R+14. There was no difference in Cr T1/2 or the C glycine red cell mean 

 life span pre- and postflight. There was no change in the rate of 

 erythropoiesis. Reticulocyte counts were low at recovery. 



CONCLUSIONS : A decrease in red cell mass is a constant occurrence in space 

 flight, and the decrease does not seem to be caused by intravascular 

 hemolysis. Splenic trapping of red cells is a plausible but untested 



explanation for the loss. After the initial loss, there is at least a 30-day 

 delay before the red cell mass begins to reconstitute itself indicating bone 

 marrow inhibition. Two unrelated biological changes may have been the cause 

 of bone marrow inhibition. First, the plasma volume decreased causing tissues 

 sensitive to peripheral hematocrit changes to not recognize the decrease in 

 red cell mass. Later, serum phosphorus rose causing increased red cell 

 release of oxygen. The oxygen-sensitive kidney would counter this by 

 decreasing erythropoietin production. This combination of events probably 

 explains the observed decrease in reticulocyte counts. 



PUBLICATIONS : 291, 292, 293, 296 



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