Acute effects of hypoxia on renal and endocrine function in normal humans

The effects of hypoxia upon renal and endocrine function are unclear. Normal water-loaded subjects were exposed to hypoxia for 1 h (inspired PO2 = 74 Torr) in a decompression chamber (5,100 m, n = 8) or by breathing 10.5% oxygen at ambient pressure (n = 4). In four of eight subjects exposed to hypobaric hypoxia: urine flows (V) decreased (mean = 56%), urine osmolality increased (340%), plasma arginine vasopressin (AVP) increased (2,700%), plasma cortisol increased (256%), and mean blood pressure (BP) decreased (18%). V correlated inversely with AVP (r = 0.71, P less than 0.01) while AVP increases correlated with falls in mean BP (r = 0.72, P less than 0.05). Similar results were observed in the subjects exposed to normobaric hypoxia. Plasma aldosterone fell in the four subjects who maintained V on exposure to hypobaric hypoxia, but plasma renin activity did not change. In both groups prolactin levels were variable and solute and creatinine excretion were unchanged. No changes were observed in controls or in subjects exposed to hypobaria alone. Acute hypoxic exposure may produce significant hypotension with consequent increased AVP secretion resulting in diminished V.