Long-term dynamics of the functional state of the rat body after combined exposure to space flight factors in a ground experiment

Abstract

Abstract. During space flight (SF), microgravity and cosmic radiation act on living objects simultaneously, negatively affecting the state of the body and leading to the development of dysregulatory shifts and various pathologies, and the presence of additive and synergistic influences of SF factors can significantly aggravate and increase the severity of the expected effects. At the moment, there is no clear idea about the combined effect of radiation and microgravity on the human body, and about the mechanisms of development of delayed negative consequences years after the commission of SF. The key role in maintaining the health of the crew will be played by the individual characteristics of the body of astronauts and astronauts, which include the degree of tension of the main regulatory systems, the level of resource mobilization, the degree of readaptation to terrestrial conditions. In this regard, the problem of complex action of SF factors is of great interest, which increases the importance of conducting research on modeling various SF factors and their combinations to predict their effects during space missions and in the post-flight period.

Objective: to evaluate the effect of the combined effect of simulated microgravity and ionizing radiation (IR) on the rat body within 12 months after exposure.

Methods: two-week hindlimb unloading (HU), single acute gamma irradiation at a dose of 1,5 Gy, ECG, heart rate variability, laser correlation spectroscopy, measurement of body weight and heart of rats.

Results. In the IR+HU group one can observed a decrease in the body weight of rats throughout the experiment, most pronounced from 9-12 months. The combined effect of two SF factors after 1 year led to an increase in the percentage of particles with a small hydrodynamic radius of about 4-8 nm and particles with a radius of about 27 nm in the blood serum. ECG analysis revealed a decrease in the amplitude of the R2 wave at a period of 6 months in the IR group and in the group with combined exposure compared with the HU group. After 12 months in the group IR+HU has been identified a tendency to increase the duration of QTc intervals and the duration of the RR interval compared to other groups. Only in the IR group, after 3 months, a shift in the vegetative balance towards parasympathetic predominance was revealed compared with the control and the HU group. Cardiac arrhythmias were observed throughout the experiment without significant differences between the groups. In the IR+HU group was showed an increase in the heart mass index after 3 and 12 months compared with other experimental groups.

Conclusion: the results show that the combined effect of two simulated SF factors, ionizing radiation and microgravity, leads to a more pronounced or longer-lasting change in the functional state of various body systems, compared with the effects of the factors considered separately.