EFFECTS OF MICROGRAVITY AND INCREASED GRAVITY ON BONE-MARROW OF RATS

Astronauts have a reduction in their red cell mass when exposed to mic rogravity. This is probably mainly due to a physiological response to decreased energy requirements. Further studies of erythropoiesis were carried out in microgravity on rats flown on Soviet Biosatellite 2044 and in hypergravity by centrifugation at 2G. Studies included: bone ma rrow cell differential counts, clonal studies of RBC colony formation, and plasma erythropoietin determinations. In the bone marrow of Cosmo s flight animals there was a slight increase in granulocytic cells and in centrifuged animals, a slight decrease in the percentage of erythr oid cells which led to an increased M:E ratio. The bone marrow cells o f flight and centrifuged rats responded to erythropoietin. Cosmos flig ht animals' cells formed fewer CFU-E than the controls but this was re versed in the centrifuge studies. There were no essential differences in the erythropoietin levels of test groups as compared to control gro ups.