Human amino acid excretion patterns during and following prolonged multistressor tests

Area of Science:

• Human physiology
• Aerospace medicine
• Biochemistry

Background:

• Simulated flight environments present complex physiological stressors.
• Understanding human physiological adaptation to flight conditions is crucial for crewed missions.
• Biochemical markers can potentially indicate physiological stress responses.

Purpose of the Study:

• To assess physiological responses to simulated flight conditions.
• To investigate the impact of environmental dryness and hypoxia on human physiology.
• To identify sensitive biochemical markers, specifically urinary amino acids, for stressor differentiation.

Main Methods:

• Feasibility study involving two male subjects in a factorial experiment of simulated flights.
• Collected physiological data during baseline, experimental (uncomplicated flight, dryness, hypoxia, combined), and recovery periods.
• Analyzed urinary nitrogenous metabolites, including individual amino acids, for stressor sensitivity.

Main Results:

• Identified specific amino acids exhibiting high sensitivity to different stressor complexes (dryness, hypoxia, combined).
• Urinary amino acid profiles differentiated between uncomplicated flight, single, double, and triple stressor conditions.
• Amino acid levels also distinguished between experimental and recovery physiological states.

Conclusions:

• Urinary amino acids serve as sensitive indicators of physiological stress during simulated flights.
• These metabolites can effectively differentiate the impact of various complex stressors encountered in flight.
• Findings support the potential use of amino acid analysis for monitoring astronaut health and stress.