Circadian urinary excretory patterns in an Antarctic environment

Area of Science:

• Human physiology
• Environmental physiology
• Antarctic research

Background:

• Understanding physiological adaptations to extreme environments is crucial.
• Antarctic expeditions present unique challenges, including continuous daylight and altered activity patterns.
• Previous research on human physiological responses in Antarctica is limited.

Purpose of the Study:

• To investigate changes in urine volume and electrolyte excretion during an Antarctic expedition.
• To assess the preservation of circadian excretion patterns in continuous daylight.
• To evaluate the reliability of short-term urine collections for predicting 24-hour excretion.

Main Methods:

• Four participants on a five-week Antarctic expedition provided 13 overnight (9-hour) and 24-hour urine collections.
• Collections were divided into wake (0700-2200 h) and sleep (2200-0700 h) periods.
• Pre-expedition control collections were made in Christchurch.

Main Results:

• Mean 24-hour urine volume increased by 500 ml, and sodium excretion by 50 mmol.
• Potassium, urea, and creatinine excretions showed no significant changes.
• Circadian excretion patterns were preserved, but 9-hour predictions of 24-hour excretion were unreliable.

Conclusions:

• Antarctic expeditions can lead to increased urine volume and sodium excretion.
• Circadian rhythms are maintained in Antarctic continuous daylight conditions.
• Short-term urine collections are not reliable for estimating 24-hour excretion in this population.