AJP - Regulatory, Integrative and Comparative Physiology, Vol 250, Issue 6 1028-R1033, Copyright © 1986 by American Physiological Society
Reduced osmotic and nonosmotic release of vasopressin after meclofenamate in the conscious dog
B. R. Walker, A. L. Erickson, P. E. Arnold, T. J. Burke and T. Berl
Both in vivo as well as in vitro experiments suggest that prostaglandins
(PG) may influence arginine vasopressin (AVP) release. Recent studies on
conscious dogs have shown that cyclooxygenase inhibition with meclofenamate
reduces basal AVP release as well as AVP release in response to hypoxia.
The current experiments were performed in order to test whether PG
synthesis inhibition affects osmotic- and nonosmotic-stimulated AVP release
in a similar manner. Osmotic AVP release was tested by slowly infusing
hypertonic saline intravenously in water-diuresing dogs and serially
sampling plasma for AVP concentration. Experiments were performed both with
and without meclofenamate (2 mg/kg and 2 mg X kg-1 X h-1 iv) pretreatment.
AVP release to a comparable osmotic stimulus was greatly reduced after
meclofenamate administration. Nonosmotic AVP release was tested by inducing
systemic hypotension with an intravenous infusion of nitroprusside.
Hypotension was associated with an increase in AVP concentration, which was
partially blunted after meclofenamate administration. Experiments performed
with only a saline vehicle administered showed no decrease in AVP release
in response to comparable hypotension. The findings of these studies
suggest that endogenous PG may be involved in both osmotic and nonosmotic
AVP release in the conscious dog.
