[Evaluation of the 7-day immersion effect on the renal excretory function]

Area of Science:

• Human physiology
• Renal function studies
• Environmental physiology

Background:

• Water immersion is a model for microgravity simulation.
• Understanding renal responses to immersion is crucial for spaceflight adaptation.
• Previous studies have shown varied effects on kidney function.

Purpose of the Study:

• To investigate the impact of 7-day head-out water immersion on renal function.
• To assess urinary excretion of key metabolites and electrolytes.
• To evaluate changes in glomerular filtration and tubular reabsorption.

Main Methods:

• Eight healthy male subjects (21-26 years old) underwent 7-day head-out water immersion.
• Urine samples were analyzed for total protein, creatinine, urea, uric acid, glucose, electrolytes (K, Na, Ca, P, Mg), proteins, and enzymes.
• Uroproteinogram and uroenzymogram analyses were performed.

Main Results:

• No significant changes in kidney function were observed.
• Glomerular filtration and tubular reabsorption remained unaffected.
• Electrolyte excretion normalized quickly despite initial diuresis.
• Increased excretion of creatinine, urea, Ca, Mg, and P suggests muscle catabolism.

Conclusions:

• Seven-day head-out water immersion does not adversely affect kidney function in healthy young men.
• Renal filtration and reabsorption capacities are maintained during short-term immersion.
• Observed metabolic changes are likely due to skeletal muscle catabolism rather than renal impairment.