Journal of Applied Physiology, Vol 61, Issue 1 150-154, Copyright © 1986 by American Physiological Society
Aldosterone response to angiotensin II during hypoxemia
G. L. Colice and G. Ramirez
Exercise in humans causes increases in plasma renin activity (PRA) and
plasma aldosterone concentrations (PAC) except when performed at high
altitude or while the subjects breathe hypoxic gas. Under those conditions,
PRA increases with exercise but PAC does not. We speculated that the PAC
suppression during hypoxemic exercise was due to hypoxemia-induced release
of a circulating inhibitor of angiotensin II-mediated aldosterone
secretion. To test this hypothesis, we measured the PAC response to graded
infusions of angiotensin II during hypoxemia and normoxemia. Eight normal
volunteers were given increasing doses of angiotensin II (first 2 ng X kg-1
X min-1 and then 4, 8, and finally 12 ng X kg-1 X min-1, each for 20-min
periods) on 2 separate days, once while breathing room air and the other
day while breathing hypoxic gas adjusted to maintain the subjects'
hemoglobin saturation at 90%. The PAC response to different doses of
angiotensin II did not significantly differ during hypoxemia from
normoxemia. We conclude that our model of hypoxemia does not cause release
of an inhibitor of angiotensin II-mediated aldosterone release.
