Objectives
The red blood cell (RBC) plays an integral part in the transport of oxygen and carbon dioxide within the body. It is critical to the bodies' health that a normal number of RBCs is maintained.
An experiment, flown aboard a 9-day Shuttle mission, revealed a 12% decrease in total blood volume within the first 24 hours of space flight. The associated decrease in blood plasma volume resulted in an increase in packed cell volume (central body hematocrit). The release and serum levels of the red blood cell producing hormone erythropoietin were declined at the same time. These findings indicated that the release of newly produced RBCs, controlled by erythropoietin, stopped immediately after entering microgravity.
It was therefore hypothesized that the immediate down-regulation of RBC production during space flight is accomplished through ineffective erythropoiesis resulting from decreased erythropoietin release and reduced serum levels. Researchers believe that long-term exposure to microgravity can cause a substantial decrease in the number of red blood cells in the cardiovascular system, causing a stage of anemia.
Shuttle-Mir Missions Approach
Following the infusion of labeled RBCs, additional blood samples were drawn over the next weeks to count the marked RBCs still present in the blood stream. From this number, the RBCs life span was calculated. Also, the levels of the hormones and other substances involved in the production and destruction of RBC's, such as erythropoietin, haptoglobin, ferritin and iron, were analyzed from the blood samples.
Results
Overall, it was concluded that the adaptation processes to the microgravity environment concerning RBC mass and survival represent a state of anemia and that anemia can be used as the model to understand the mechanisms of erythropoiesis during space flight.
Publications Principal Investigators
Svetlana Ivanova, Ph.D.
Mir-18
To count RBC mass, blood was drawn and the RBCs of each sample were marked with the chromium isotope 50Cr. A known amount of the marked blood was reinfused into the veins of the test subjects. Another blood sample, drawn two hours later, was used to analyze the RBC mass by measuring the proportion of marked RBCs to unmarked ones.
The investigation revealed a decrease in the serum concentrations of the RBC production hormone erythropoietin during space flight. On landing day the values were decreased in 2 of the 3 crewmembers and significantly elevated in all three crewmembers nine days after landing. The number of RBCs counted during and after the space flight was also lower than before launch. On landing day, the RBC mass was significantly decreased compared to preflight
measurements.
None available at this time.
Helen Lane, Ph.D.
NASA/Johnson Space Center
Institute of Biomedical Problems
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Curator:
Julie Oliveaux
Responsible NASA Official: John Uri |
Page last updated: 07/16/1999
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