AJP - Heart and Circulatory Physiology, Vol 243, Issue 4 560-H565, Copyright © 1982 by American Physiological Society
Systemic and regional hemodynamic effects of endogenous vasopressin stimulation in rats
F. Charocopos, P. Hatzinikolaou, W. G. North and H. Gavras
We investigated the systemic and regional hemodynamic alterations induced
in normotensive anephric rats by stimulation of endogenous vasopressin with
an acute sodium and fluid load and following vasopressin inhibition with a
specific antagonist of its vasoconstricting action. Blood pressure and
total peripheral resistance were significantly higher and cardiac output
was lower in rats with stimulated vasopressin, and all were reversed to
near control levels in rats receiving the vasopressin inhibitor. Regional
blood flows were diminished in most organs and local vascular resistance
was elevated compared with control animals, but the magnitude of change
varied widely. In fact, heart blood flow did not decrease significantly and
brain blood flow actually increased indicating small or no change in
vascular resistance of these organs. Moreover, fractional distribution of
the diminished cardiac output to these organs was significantly higher, so
that blood flow to vital organs was maintained at the expense of blood flow
to other tissues. In rats that received the vasopressin antagonist after
the saline infusion, regional blood flows were similar to those of control
animals. Blood pressures at the base line and after hypertonic NaCl
infusion correlated closely with the corresponding plasma levels of control
and stimulated vasopressin.
