AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 1 18-R22, Copyright © 1986 by American Physiological Society
ACTH, cortisol, and renin responses to arterial hypotension in sheep
C. E. Wood
This study was designed to investigate adrenocorticotropin (ACTH),
cortisol, and renin responses to nitroprusside-induced hypotension in adult
sheep. Five sheep were surgically prepared with carotid arterial skin loops
at least 1 yr before these experiments. After catheterization of the
carotid arteries and external jugular veins the sheep were infused with
nitroprusside intravenously at rates of 0, 10, 15, or 20 micrograms . kg-1
. min-1 for 10 min. Nitroprusside produced significantly dose-related
decreases in mean arterial pressure and increases in heart rate, plasma
ACTH and cortisol concentrations, and plasma renin activity. Hematocrit was
significantly increased in the 10- and 20-micrograms . kg-1 . min-1 groups
during nitroprusside, probably reflecting contraction of the spleen. After
the end of the period of hypotension, hematocrit was significantly
decreased in all nitroprusside infusion groups, probably reflecting
transcapillary movement of fluid into the vascular space. A posteriori
analysis of the data suggests that the ACTH response to nitroprusside
infusion was better predicted by the nadir in mean arterial pressure and
that the renin activity response was better predicted by the initial rate
of decrease of mean arterial pressure during nitroprusside infusion.
