title: Renin, aldosterone, and converting enzyme during exercise and acute hypoxia in humans.
abstract: The possibility that hypoxia might inhibit the secretion of angiotension-converting enzyme (ACE) would explain the low concentrations of aldosterone reported in humans at high altitude. To observe the effect of such a reduction in ACE concentration on the plasma aldosterone concentration (PAC) four subjects performed mild exercise throughout a 2-h study so as to elevate their plasma renin activity (PRA). After the first 60 min breathing air they were switched to breathing 12.8% O2 (4,000 an altitude equivalent). Venous samples were taken at intervals for hormone analysis. Results showed the expected rise of PRA and PAC both tending toward a plateau after about 45 min. There was no significant change in ACE activity (F = 0.065). Hypoxia produced a further 50% rise in PRA but a fall in PAC and a 30% reduction in ACE activity. Angiotensin I concentrations closely followed PRA throughout (r = 0.984). These results indicate that during exercise acute hypoxia changes the usual close relationship between PAC and PRA by reducing ACE activity.
mesh_terms: D000208:Acute Disease; D000328:Adult; D000450:Aldosterone / Q000097:blood*; D006801:Humans; D000860:Hypoxia / Q000201:enzymology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*; D005082:Physical Exertion; D012016:Reference Values; D012044:Regression Analysis; D012083:Renin / Q000097:blood*
chemical_list: D000450:Aldosterone; D007703:Peptidyl-Dipeptidase A; D012083:Renin