Serum erythropoietin titers during prolonged bedrest; relevance to the ?anaemia? of space flight

Abstract

The overall objective of these studies was to test the hypothesis that the suppression of erythropoiesis, which occurs during both spaceflight and bedrest, was mediated by reduction in circulating levels of erythropoietin. In each of two 7-day studies, groups of subjects were exposed to either horizontal or 6 degrees head-down tilt bedrest and no evidence was obtained to suggest that the erythropoietic effects were dependent on the angle of recumbency. An additional study involved six men who were exposed to horizontal bedrest for 28 days. Serum erythropoietin titers were not significantly depressed in any of the subjects but total red cell volume was decreased. Absolute increases in red cell numbers and reductions in plasma volume both elevate the haematocrit, but our data suggest that the mechanism of erythrosuppression in these two instances may be different.

Haemoglobin mass alterations in healthy humans following four‐day head‐down tilt bed rest

“…Admittedly, a near complete cessation of RBC destruction would be required to account completely for a 4% increase in Hbmass within 4 days. No previous studies have provided evidence for an increase in Hbmass/RCV during HDTBR of 5-16 days duration (Convertino et al 1984(Convertino et al , 1986aDunn et al 1984;Williams & Convertino, 1988;Branch et al 1998;Millet et al 2001;Linnarrsson et al 2015), and we are the first to have measured Hbmass/RCV in the upright, seated position and after graded exercise testing following HDTBR. This unique aspect of our study design leaves open the possibility that the return to orthostasis and graded exercise testing prior to assessment of Hbmass might have influenced our finding of a transient increase in Hbmass.…”

“…, a , b ; Dunn et al . ; Leach & Johnson, ; Williams & Convertino, ; Branch et al . ; Millet et al .…”

“…; Dunn et al . ; Millet et al . ), but few data are available on changes in Hbmass/RCV following short‐term HDTBR.…”

“…It has been proposed that these responses trigger neocytolysis in spaceflight (Alfrey et al 1996a(Alfrey et al ,b, 1997; therefore, a loss in Hbmass/RCV might be expected to occur over a similar time frame following HDTBR. Some studies have reported decreases in Hbmass/RCV during days 7-10 of HDTBR (Convertino et al 1984;Dunn et al 1984;Millet et al 2001), but few data are available on changes in Hbmass/RCV following short-term HDTBR. Measuring Hbmass following rather than during HDTBR enables a more consistent comparison with data collected following spaceflight; to our knowledge, there are no published measurements of Hbmass/RCV during spaceflight.…”

Effects of Iron Overload and Oxidative Damage on the Musculoskeletal System in the Space Environment: Data from Spaceflights and Ground-Based Simulation Models

“…The model of HDBR, which has been used as a model of spaceflight, is associated with cephalic fluid shift. Unlike spaceflight results, although RBC mass decreased during bed rest [ 38 , 39 ], no changes were observed in SF. Nonetheless, a decreased concentration of serum TfR was found in a long-duration HDBR [ 16 ].…”