Metabolic Responses of the Female Body during a Short-term Isolation in Hermetic Environment

The program of the Moon-2015 eight-day experiment simulating a lunar flyby to study the mechanisms controlling the female body adaptation to the conditions of isolation in a hermetically sealed environment (IHE) during interplanetary voyages included the measurement of 42 biochemical indices characterizing the state of organs and tissues, as well as the main metabolic pathways, in six female volunteers aged from 25 to 34 years. Venous blood samples were collected 25 days before the IHE start, 1 h after centrifugation (+Gz, 2g, 21 min) on a short-radius centrifuge (SRC) before the IHE start, on day 5 of the IHE, immediately after the IHE completion and one hour after centrifugation (+Cz, 2g, 30 min) upon the IHE completion. The following signs of expressed stress responses were observed after the first centrifugation: the concentrations of glucose, β-hydroxybutyrate (β-HB), and bicarbonate (BC) significantly increased, and the creatine phosphokinase (CPK) activity also increased, which was accounted for by muscle isozymes. Mild symptoms of hypodynamia were observed on day 5 of IHE: the concentrations of glucose, albumin, calcium, and chlorides, as well as the activities of cholinesterase (CHE) and lactate dehydrogenase (LDH), moderately decreased; in contrast, the lipase activity and the magnesium and phosphorus concentrations increased. No significant differences were recorded between the values shown in the majority of indicators after the IHE and the baseline values. The changes due to centrifugation resembled the previous pattern of exposure to hypergravitation (HG), but they were less intense and did not involve all indices, e.g., the values of CPK activity and its muscle isozyme, as well as the β-HB concentrations, did not differ from the baseline values, whereas the BC level decreased, which could be associated with both the hypodynamic effect and a progress in HG training. Thus, HG training on a CFG led to the development of a stress response marked for elevated blood glucose and cholesterol and elevated CPK activity. The living under the IHE conditions even for a limited period of time led to the appearance of metabolic signs of hypodynamia, which were quickly compensated upon the completion of the IHE.