THE ANEMIA OF MICROGRAVITY AND RECUMBENCY - ROLE OF SYMPATHETIC NEURAL CONTROL OF ERYTHROPOIETIN PRODUCTION

We hypothesize that reduced sympathetic stimulation of erythropoietin production may maintain the anemia which develops in virtually all spa ce travellers. We tested this hypothesis in a human model of reduced s ympathetic activity. Thirty-three patients with the Bradbury-Eggleston syndrome were divided into three groups according to their hemoglobin (Hgb) level. Patients with low Hgb had lower upright norepinephrine a nd lower upright renin. Patients with anemia also had inappropriately low plasma erythropoietin levels. We administered recombinant erythrop oietin (Epogen) 25-50 units/kg s.c. 3 times per week and found that th e anemia seen in autonomic failure could be reversed by this treatment . These results support the hypothesis that erythropoiesis is modulate d by the sympathetic nervous system and that such mechanisms may also operate in the microgravity environment where sympathetic activity is reduced.