Renal and hormonal responses to acute hypoxia in normal individuals

We studied, in normal volunteers, the effects of 1 hour of hypoxia on the concentration of angiotensin-converting enzyme and bradykinins, along with previously measured parameters of renal and endocrine function. Ten men, 18 to 42 years of age, undergoing water diuresis, breathed a low-oxygen mixture (five breathed 10.5% O2 and five 12% O2); all breathed 21% O2 on a control day. Measurements included mean blood pressure and heart rate every 2 to 3 minutes; plasma levels of renin activity, aldosterone, arginine vasopressin, norepinephrine, and bradykinin, and angiotensin-converting enzyme activity, before and at the end of gas breathing; and urine volume (UV), creatinine, Na+, and bradykinin concentration. Arterial blood gases and effective renal plasma flow were determined at the end of gas breathing only. Mean values +/- SEM for arterial blood gases with low O2 were pH 7.39 +/- 0.02, PO2 46 +/- 2 torr, PCO2 39 +/- 2 torr (12% O2) and 7.48 +/- 0.01, 35 +/- 1 torr, 33 +/- 1 torr (10.5% O2). Responses were otherwise identical in both groups, and data were combined for analysis. With hypoxia, heart rate and effective renal plasma flow increased significantly, P less than 0.005; no changes occurred in Uv, urine Na+ concentration, glomerular filtration rate, plasma or urine bradykinin concentration, serum angiotensin-converting enzyme activity, plasma renin activity, plasma aldosterone concentration, plasma arginine vasopressin concentration, or plasma norepinephrine concentration.(ABSTRACT TRUNCATED AT 250 WORDS)