Objectives
The red blood cell (RBC) performs the vital task of transporting oxygen from the lungs to all the cells of the body. Any change in the RBC characteristics ultimately affects the efficiency of oxygen transport and can have detrimental effects on a person's health. Changes in erythrocyte (red blood cells) mass, osmotic stability and metabolic parameters for RBC's as well as changes in RBC shape have been observed during previous space flights.
The purpose of this experiment was to determine and evaluate the functional status of erythrocytes during and after space flight. In particular the parameters of energy metabolism of RBC's, the oxidation-reduction system (uptaking and release of oxygen molecules), and the condition of the plasma membrane were of special interest.
Shuttle-Mir Missions Approach
The following erythrocyte characteristics were determined from all blood samples: (1) RBC energy metabolism was determined by measuring the content of several substances involved in energy metabolism of red blood cells, such as adenosine triphosphate (ATP), 2,3-diphosphoglycerate (2,3 DPG), glycolysis rate, activity of lactate dehydrogenase (LDH) and hexokinase (HK). (2) The oxidation-reduction system was determined by the content of reduced glutathione and glucose 6-phosphate dehydrogenase activity. (3) The condition of plasma membrane was evaluated based on parameters describing the lipid and phospholipid composition and the activity of the transport ATPases for sodium ions (Na+), potassium ions (K+), calcium ions (Ca++) and magnesium ions (MG++).
Results
The activity of glucose 6-phosphate dehydrogenase was decreased in all three subjects during space flight and also postflight. A reduced gluathione content was noted in two subjects during and after space flight.
Declined activity was noted for Na+, K+ and Ca++ ATPases. The scientists believe that these observations were caused by changes in the plasma membrane's physical and chemical properties and by the composition of its main components, the lipids and proteins.
An elevated cholesterol level in the erythrocytes was first noted 14 days after launch and observed until 9 days after landing. The elevated cholesterol content indicated a change in the membrane's phase state, causing an increase in the membrane's rigidity and a possible reduction of its deformability.
Overall, the results of this investigation showed significant inflight changes in erythrocyte metabolism and membrane condition for all subjects. The observed destabilization of the cell membrane may have resulted from changes in the blood plasma, caused by shifts in hormone levels, electrolyte balance and lipid metabolism. Direct effects of space flight on the quality of erythrocytes cannot be excluded.
Earth Benefits Publications Principal Investigators
Svetlana Ivanova, Ph.D.
Mir-18
The biochemical characteristics of erythrocytes were studied before, during and after space flight using erythrocytes obtained from venous blood samples. Three times during flight and twice postflight blood samples were collected on three subject. Preflight samples were used to gain a baseline for each astronaut with which the inflight and postflight results were compared.
The analyzed data showed that starting two weeks after launch the ATP level decreased in the erythrocytes, mainly in one subject. Postflight measurements showed an increased ATP level in all three crewmembers. Elevated lactate dehydrogenase levels were measured on landing day, indicating the prevalence of anaerobic processes.
By understanding how red blood cells (RBC's) are affected in their function by microgravity, researchers gain more knowledge of how RBCs function in general.
Rice, B. L.and H. Lane. Dietary studies in the joint US-Russian space program. J Am Diet Assoc. 1997, 97 (suppl 2), p. 127-128.
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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