AJP - Regulatory, Integrative and Comparative Physiology, Vol 233, Issue 5 239-R242, Copyright © 1977 by American Physiological Society
Blood pressure vulnerability to volume contraction: regulation by adrenal cortical hormones
T. Waldinger, J. F. Seaton and T. S. Harrison
Although the unique sensitivity of blood pressure to hemorrhage after
adrenalectomy can be overcome by adrenocortical hormones the specificity of
this steroid effect is not known. Under pentobarbital anesthesia five
groups of six adult male Sprague-Dawley rats were bled into a 0.9%
saline-primed pressure-balanced reservoir. A mean arterial pressure of 50
Torr was maintained for 3 h. When compared to normal rats, those with
adrenalectomy showed significantly lowered bleeding volume (P less than
0.05 to less than 0.001). In untreated adrenalectomized rats 120 min
following hemorrhage, saline was consistently taken up from the reservoir
to maintain blood pressure at 50 Torr. Deoxycorticosterone-cortisol
(intravenous bolus coupled with infusion) restored bleeding volume to
normal in adrenalectomized rats. Aldosterone (constant infusion) also
protected bleeding volume after adrenalectomy, P less than 0.05 to less
than 0.01, but this effect was significantly less striking than that of
cortisol 180 min after the onset of bleeding, P less than 0.001. Sham
adrenalectomy did not affect bleeding volume. Aldosterone appears to be
effective in restoring normal bleeding volume sensitivity after
adrenalectomy but this effect of aldosterone is less sustained than that
seen with cortisol.
