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Urinary leukotriene E4 levels increase upon exposure to hypobaric hypoxia
J M Roach1, S R Muza, P B Rock
1Altitude Physiology and Medicine Division, US Army Research Institute of Environmental Medicine Natick, Mass, USA.
Study Objective:
To determine whether urinary leukotriene E4 (uLTE4) levels increase upon exposure to high altitude, and also to ascertain the relationship between uLTE4 levels and symptoms of acute mountain sickness (AMS).
Design:
Prospective, unblinded, single-factor (altitude) experimental study.
Settings:
US Army research laboratory facilities at sea level ([SL] 50 m), 1,830 m, and 4,300 m.
Participants:
Eight healthy male subjects ranging in age from 19 to 24 years.
Measurements:
uLTE4 levels and symptoms of AMS were measured at just above SL (50 m), 3 1/2 days after being transported from SL to moderate altitude (MA) (1,830 m), and 1 1/2 days after ascent from 1,830 to 4,300 m (high altitude [HA]). Symptoms of AMS were assessed using standard indexes derived from the Environmental Symptoms Questionnaire weighted toward cerebral (AMS-C) and respiratory (AMS-R) manifestations. Oxygen saturation was measured noninvasively by pulse oximetry at SL and HA.
Results:
The mean (+/-SEM) uLTE4 levels (pg/mg creatinine) were 67.9 (+/-13.2) at SL; 82.3 (+/-5.5) at MA; and 134.8 (+/-19.4) at HA (p < 0.05 comparing HA with SL and MA).
Conclusions:
We conclude that uLTE4 levels increase shortly after exposure to HA even after staging for 4 days at MA. Although this study does not clearly demonstrate a relationship between uLTE4 levels and symptoms of AMS, it supports the hypothesis that leukotrienes may be involved in the pathophysiologic state of AMS.