Delayed effects of simulated space flight factors

Abstract

Currently, in the field of space medicine, there is an acute problem of ensuring crew safety during long-term space missions beyond near-earth orbit. The crew must be protected from potential extreme conditions, as well as preventing long-term consequences of adverse effects of the space environment.
Objective: To simulate in rats responses to the main factors of space flight, i.e., microgravity and ionizing radiation; to analyze at 6 mos and at 6 wks the long-term consequences of exposure to these factors; to study the dynamics of the detected changes.
Methods: Simulation of microgravity by 2-wk anti-orthostatic hanging (AOH); simulation of cosmic radiation by exposure to gamma radiation with an acute dose of 1.5 gy; laser correlation spectroscopy; electrocardiography; calculation of blood leukocytes; measurement of serum corticosterone. The long-term effects of radiation exposure were analyzed 6 wks after exposure, and the anti-orthostatic effects were analyzed at 6 mos.
Results: Simulated microgravity led to a decrease in the immunological reactivity and an increase in the products of cellular destruction in the blood serum. The subfractional composition of the blood serum after simulated microgravity was completely restored at 1 mo, but at 6 wks after irradiation, normalization of serum homeostasis had not occurred. The simulated factors of space flight led to non-specific changes in myocardial electrical conductivity that were manifested during the long-term period of readaptation. Within 2 weeks after the end of AOH the QT and QTc intervals were lengthened, and after 2 and 3 mos, the average RR interval was shortened and the heart rate was increased. Irradiation had a greater effect on the myocardium, causing electrophysiological disorders, consisting of a decrease in the amplitude of the P-wave, a shortening of the duration of
the R-wave, an elongation of the average RR interval, and a decrease in heart rate. These shifts occurred during all 6 wks of the experiment. During 3-6 wks, an increase in the duration of the PQ interval was recorded, indicating a slowing of atrioventricular conduction. Minor cardiac arrhythmias were detected within 6 wks after radiation exposure. Broadening of the QRS complex and prolongation of the QT and QTc intervals were observed within 1 mo after exposure. Thus, this study of the effects of simulated
space flight factors showed that most effects were reversible, but some damage to myocardial electrical conductivity persisted.
Conclusion: A rat model of individual factors of space flight showed that some resulting changes are prolonged. In this regard, it can be recommended that screening tests be conducted and that the health of astronauts be monitored throughout their life for timely detection of possible alterations of physiological functions that might occur during extended periods following space missions. Laser correlation spectroscopy can be used as an additional integral method for assessing the long-term effects of
space flight factors.