Journal of Applied Physiology, Vol 62, Issue 4 1538-1543, Copyright © 1987 by American Physiological Society
Effect of sodium depletion on peripheral vascular responses to heat stress in baboons
D. W. Proppe
The cutaneous vasodilation and renal vasoconstriction in baboons during
environmental heating (EH) appear to be produced predominantly by
sympathetic vasoconstrictor withdrawal and activation of the
renin-angiotensin system, respectively. Since these mechanisms may be
influenced differently by sodium depletion, this study examined the
hypothesis that sodium depletion would have a differential effect on
cutaneous and renal vascular responses to EH. Sodium depletion was produced
in chronically instrumented baboons by placing them on low-salt intake for
8-19 days along with diuretic administration. EH consisted of exposing the
baboon to an ambient temperature of 40-42 degrees C until core temperature
(Tc) reached 39.8-40.0 degrees C. Both control plasma renin activity (PRA)
and the rise in PRA with Tc during EH were considerably larger in
sodium-depleted baboons. However, the magnitudes of the progressive
increases in iliac vascular conductance (used as an index of hindlimb
cutaneous vasodilation) and renal vascular resistance with rising Tc during
EH were unaltered by sodium depletion. Therefore, neither cutaneous nor
renal vascular responses to EH are influenced by elevated PRA and other
changes accompanying sodium depletion in the baboon.
