AJP - Heart and Circulatory Physiology, Vol 256, Issue 1 94-100, Copyright © 1989 by American Physiological Society
Regional adrenal blood flow during hypoxia in anesthetized, ventilated dogs
M. K. Nishijima, M. J. Breslow, H. Raff and R. J. Traystman
Department of Anesthesiology and Critical Care Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland 21205.
The effect of hypoxic hypoxia (HH) and carbon monoxide hypoxia (COH) on
adrenal medullary (MQ) and cortical (CQ) blood flow (radiolabeled
microsphere technique) was studied in pentobarbital sodium-anesthetized,
mechanically ventilated dogs. Animals were exposed to 60 min of hypoxia
(arterial O2 content 8 vol%) induced by adding either nitrogen (HH, n = 6)
or carbon monoxide (COH, n = 6) to the inspired gas. Whole adrenal Q and CQ
increased by 70 and 50%, respectively, with HH but were unchanged during
COH. MQ, however, increased threefold during both HH and COH. HH and COH
both increased arterial levels of epinephrine, corticosteroids, and
adrenocorticotropic hormone (ACTH). To determine whether the increase in CQ
during HH was because of HH-induced increases in mean arterial blood
pressure (MAP, approximately 20 mmHg), an additional group of animals (n =
6) was exposed to HH but had MAP maintained at control levels using a
pressurized-bottle system. MAP control did not alter the CQ response to HH.
We conclude that MQ appears to be associated with medullary secretory
activity during hypoxia and that HH and COH stimulate adrenal medullary
secretion equally. In contrast, CQ increases only with HH, despite similar
increases in ACTH and corticosteroid levels during HH and COH, suggesting
that an alternative mechanism is responsible for increased cortical blood
flow during HH.
