AJP - Heart and Circulatory Physiology, Vol 251, Issue 5 1009-H1016, Copyright © 1986 by American Physiological Society
Pulmonary vasoactive effects of exogenous and endogenous AVP in conscious dogs
D. P. Nyhan, H. S. Geller, H. M. Goll and P. A. Murray
Our objectives were to investigate the extent to which both exogenously
administered and endogenously released arginine vasopressin (AVP) exert a
direct, vasoactive influence on the pulmonary circulation of conscious
dogs. Multipoint pulmonary vascular pressure-cardiac index (P/Q) plots were
constructed during normoxia in conscious dogs by stepwise constriction of
the thoracic inferior vena cava (IVC) to reduce Q. In intact dogs, AVP
infusion (7.6 ng X kg-1 X min-1 iv) increased (P less than 0.01) plasma AVP
from 2.3 +/- 0.4 to 280 +/- 23 pg/ml, and increased (P less than 0.01) the
pulmonary vascular pressure gradient (pulmonary arterial pressure minus
pulmonary capillary wedge pressure, PAP-PCWP) over the entire range of Q
studied. Following administration of autonomic nervous system antagonists
and a converting-enzyme inhibitor, exogenous AVP again increased (P less
than 0.01) PAP-PCWP over the entire range of Q. Generation of P/Q plots via
IVC constriction resulted in systemic hypotension (58 +/- 4 mmHg) and a
concomitant increase (P less than 0.01) in endogenous AVP release from 2.1
+/- 0.2 to 109 +/- 22 pg/ml. Following administration of the specific AVP
receptor antagonist [d(CH2)5]AVP (10 micrograms/kg iv), systemic arterial
pressure, but not PAP - PCWP, was decreased to significantly lower levels
as Q was reduced during IVC constriction. A similar response was observed
in dogs pretreated with the neurohumoral blockers. Thus exogenous
administration of AVP results in active, non-flow-dependent pulmonary
vasoconstriction. This effect is not dependent on reflex activation of the
autonomic nervous system or on the increased production of angiotensin
II.(ABSTRACT TRUNCATED AT 250 WORDS)
