[Change in hemoglobin mass during prolonged hypokinesia]

The total hemoglobin mass was measured by the carbon monoxide method in 33 male test subjects, 21 of whom were exposed to 30-day bed rest and 6 of whom were exposed to 100-day bed rest. The hypokinetic test subjects showed a decrease in hemoglobin mass by 11-24%. During readaptation the test subjects who had a noticeable reduction of hemoglobin displayed a 2.7-fold increase of the reticulocyte count. It is suggested that the gravity decrease during bed rest and antiorthostatic hypokinesia results in a reduced rate of hemoglobin synthesis in bone marrow.