Journal of Applied Physiology, Vol 48, Issue 4 606-612, Copyright © 1980 by American Physiological Society
Pulmonary inactivation of serotonin and site of serotonin pulmonary vasoconstriction
D. A. Rickaby, C. A. Dawson and M. B. Maron
To determine whether the site of serotonin-induced pulmonary
vasoconstriction is influenced by serotonin uptake and inactivation within
the lung, we utilized an isolated perfused left lower lobe of the dog lung,
which could be perfused with flow in the normal direction (i.e., blood
flowing into the lobar artery) or in the retrograde direction (i.e., blood
flowing into the lobar vein). To localize the site of vasoconstriction, we
utilized an outflow occlusion technique in which the changes in lobar
vascular resistance were divided into changes in arterial and venous
resistances. Serotonin infusion constricted vessels on the arterial side of
the site of serotonin uptake during both forward and retrograde perfusion
while having much less influence on the venous side. However, during
retrograde perfusion the serotonin infusion rate required to produce a
given increase in arterial resistance was approximately 85 micrograms/min
greater than during forward perfusion. Thus, it would appear that serotonin
was primarily an arterial constrictor in this preparation and that,
although the lung removed a substantial quantity of serotonin, the uptake
and inactivation within the lung had relatively little influence on the
site of serotonin vasoconstriction.
