AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 6 1235-R1239, Copyright © 1986 by American Physiological Society
Vasopressin responses to corticotropin releasing factor and hyperosmolality in conscious dogs
H. Raff, M. M. Skelton, D. C. Merrill and A. W. Cowley Jr
We recently reported that ovine corticotropin releasing factor (CRF)
infusion in conscious dogs elevated plasma vasopressin. The present study
examines the vasopressin, adrenocorticotropic hormone (ACTH), and cortisol
responses to CRF infusion (20 ng X kg-1 X min-1), to hypertonic saline
infusion (NaCl 0.054 meq X kg-1 X min-1), and to simultaneous coinfusion of
CRF and NaCl (CRF + NaCl) without (no-dex) or with (dex-treated)
dexamethasone pretreatment in six conscious dogs (6-8 experiments/dog). CRF
had no significant effect on plasma sodium or osmolality, blood pressure,
or heart rate. NaCl increased plasma sodium from 146 +/- 1 to 151 +/- 1
meq/l and plasma osmolality from 298 +/- 3 to 305 +/- 3 mosmol/kg.
Vasopressin increased significantly during CRF (2.1 +/- 0.5 to 4.8 +/- 1.1
pg/ml) and NaCl (1.9 +/- 0.3 to 5.0 +/- 0.8 pg/ml). Coinfusion of CRF and
NaCl resulted in a response larger than the sum of the two infusions alone
(3.0 +/- 1.6 to 31.4 +/- 18.5 pg/ml). The ACTH response to CRF (45 +/- 8 to
288 +/- 88 pg/ml) was not augmented by coinfusion with NaCl. DEX attenuated
the vasopressin and ACTH responses to each infusion. We conclude that
CRF-induced increases in vasopressin are augmented by a simultaneous
osmotic stimulus. In addition, the plasma vasopressin responses to CRF
and/or hypertonic saline infusion are inhibited by glucocorticoid
pretreatment.
