Hematological measurements in rats flown on Spacelab shuttle, SL-3

Area of Science:

• Spaceflight hematology
• Animal models in space research
• Physiological effects of space travel

Background:

• Previous research indicates spaceflight impacts astronaut red blood cell mass and white blood cell counts.
• Conflicting findings exist regarding hematological changes during space missions.

Purpose of the Study:

• To investigate the hematological effects of spaceflight on rats using the Spacelab 3 mission.
• To analyze changes in red blood cell parameters, white blood cell differentials, and erythropoietin levels.

Main Methods:

• Hematological analysis of blood samples from flight and control rats.
• Bone marrow and spleen cell differential counts.
• Erythropoietin level determination.
• Erythroid colony-forming unit assays on bone marrow cells.

Main Results:

• Statistically significant increases in hematocrit, red blood cell counts, and hemoglobin in flight rats.
• Mild neutrophilia and lymphopenia observed in flight animals.
• No significant changes in bone marrow/spleen cell differentials or erythropoietin levels.
• Increased erythroid colony formation in flight rat bone marrow cells at specific erythropoietin concentrations.

Conclusions:

• Spaceflight induced distinct hematological changes in rats, including polycythemia and altered leukocyte profiles.
• Erythropoietin levels did not change, but bone marrow responsiveness to erythropoietin was enhanced.
• Findings contribute to understanding spaceflight's impact on hematopoiesis, with novel erythropoietin and clonal assay data.