Publication Abstracts

Red cell volume and erythropoietin responses during exposure to simulated microgravity

Branch III JD, Pate RR, Bodary PF, Convertino VA
Aviat Space Environ Med 1998; 69:347-51

Abstract

In order to test the hypothesis that normal gravity is an important influence on human serum erythropoietin ([Epo]), the hematologic response to 16 d of 6° head-down tilt (HDT, n = 6 men) was compared with 16 d of normal gravity exposure (CON, n = 7 men). Prior to bed rest, CON and HDT subjects, respectively, were similar in the following characteristics (mean ± SD); age = 40 ± 3.39 ± 6 yr; height = 181 ± 5, 182 ± 6 cm; weight = 88.5 ± 11.3, 81.7 ± 12.0 kg; maximal oxygen consumption in supine 6° head-down tilt position (VO₂max) = 2.63 ± 0.38, 2.67 ± 0.52 L · min^-1; hematocrit = (Hct) 41.6 ± 22.4, 43.0 ± 3.4%; hemoglobin ([Hb]) = 15.1 ± 1.0, 14.5 ± 1.0 g · 100 ml^-1; plasma volume (PV) = 3829 ± 857, 3768 ± 512 ml; and [Epo] = 11.6 ± 2.9, 10.0 ± 6.2 mU · ml^-1. Calculated red cell volume (RCV) was greater in HDT than CON (2845 ± 410 vs. 2139 ± 253 ml, p < 0.05) at baseline. Decreases in PV (-15%, 580 ml, p < 0.05) and an insignificant decrease in RCV (-12%, 354 ml, p = 0.07) were observed in the HDT group, with a concurrent 6% increase in [Hb] (p < 0.05). PV, RCV and [Hb] remained unchanged in the CON group. [Epo] remained unchanged during HDT (12.2 ± 3.2; 10.8 ± 3.8; 11.2 ± 3.1; 11.2 ± 2.6 mU · min^-1 for HDT days 1, 2, 8 and 16, respectively). There was no difference between CON and HDT groups in [Epo] before or during HDT. It was concluded that the insignificant change (-12%) in RCV observed during HDT was insufficient to stimulate an increase in [Epo], probably because the content of oxygen in arterial blood remained unaffected. The observation that [Epo] remained unchanged despite this loss of RCV during HDT also suggests a possible decrease in the responsiveness of the erythropoietic system to [Epo].

Information on subscribing, and on obtaining copies of an article or of an entire issue.

Table of Contents for Volume 69, Number 4 of the ASEM journal.