Modifications of immunological and neuroendocrine parameters induced by head‐down bed rest (HDBR) in human healthy volunteers

Abstract

Head-down bed rest (HDBR) is used as a model for studying the physiological changes occurring in weightless during spaceflight. Exposure of animals and humans to space flight condition resulted in numerous alterations in immunological and hormonal parameters. Similar changes are observed during HDBR. The aim of this study was to investigate whether exposure to the “stress” environment are responsible for alterations in synthesis of some acute phase proteins and cytokines; and if the changes occur, there are possibility to use exercise to prevent this negative effect. In the study twelve male volunteers were subjected for 20 days to a HDBR of −6°degree; six of them were exposure to physical exercise. The parameters have been analyzed: plasma norepinephrine (NE) and epinephrine (Epi), peripheral white blood cells count (WBC), interleukin 6 (IL-6), total serum protein (TP), C-reactive proteins (CRP) and α-1antichimotrypsin (ACT). In all subjects after HDBR: CRP, Epi and NE concentrations increased significantly (p<0.05). Concentrations of TP, ACT, CRP and WBC tended to increase in all subjects after 3 day of HDBR. We didn’t observe differences between concentration of analyzed parameters in subjects maintained in non exercise group and in exercise group. The results of this study indicate that stress and sympathetic nervous system variability could play a role in inducing the changes in immunological parameters.