AJP - Regulatory, Integrative and Comparative Physiology, Vol 253, Issue 2 209-R215, Copyright © 1987 by American Physiological Society
Comparison of corticotropin-releasing factor and acetylcholine on catecholamine secretion in dogs
W. C. Engeland, M. P. Lilly, T. O. Bruhn and D. S. Gann
To test whether corticotropin-releasing factor (CRF) is a secretagogue for
adrenal secretion of catecholamines, a preparation was developed that
permits measurement of adrenal venous output in response to in vivo
arterial injection into the dog adrenal gland. Dogs were prepared with
catheters in the lumboadrenal vein for monitoring adrenal blood flow and
secretion rate of epinephrine and norepinephrine and in the lumboadrenal
and inferior phrenic arteries for adrenal injection. Under pentobarbital
anesthesia 48 h after surgery, dogs received a series of intra-adrenal
injections that included acetylcholine (0.2-200 nmol), CRF (2.0-20.0 nmol),
and diluent. There was a log dose-response relationship before epinephrine
secretion and norepinephrine secretion to acetylcholine. Adrenal injection
of CRF stimulated epinephrine and norepinephrine secretion at the highest
dose tested (20 nmol). The response observed was equivalent to the response
to 0.2 nmol acetylcholine. A similar dose of CRF given systemically
produced hypotension without stimulating catecholamine responses. Adrenal
catecholamine responses to acetylcholine were not augmented by addition of
CRF. These findings show that arterial injection of CRF into the intact dog
adrenal stimulates secretion of epinephrine and norepinephrine. However,
the low potency of CRF relative to that of acetylcholine, the lack of a
synergistic effect of CRF on catecholamine responses to acetylcholine, and
the high dose of CRF required to achieve a response suggest that CRF does
not function in the adrenal medulla as a physiologically important
secretagogue for catecholamines.
