Effect of acute exposure to hypoxia on electrolytes and water metabolism regulatory hormones

Background: Many studies suggest the hypothesis that the pathology of high altitude could be due to an early alteration of the hormones that regulate sodium homeostasis. Hypothesis: The aim of this study was to evaluate the behavior of these hormones during an acute exposure to hypobaric hypoxia. Methods: We studied 26 young healthy pilot students (23.1 ± 29 yrs) in a hypobaric chamber, for 3 h (samples collected at time 0, 120, and 180 min), at 5000 m ASL. Results: The results show an early increase of plasma renin activity (PRA) paradoxically associated to a decrease of aldosterone plasma levels. This later returned to the baseline values at 180 min, whereas PRA remained increased throughout the exposure. Both arginine-vasopressin (ADH) and the atrial natriuretic peptide (ANP) significantly increased, while a new putative hormone, the so-called digoxin-like substance (DLS) did not show significant changes. Conclusions: Our data demonstrate a specific sensitivity of the hormonal systems to hypoxia, which may be influenced by the time of the exposure. The relationship with results previously reported is also addressed.