Journal of Applied Physiology, Vol 61, Issue 1 331-337, Copyright © 1986 by American Physiological Society
Pulmonary fluid balance following pulmocutaneous baroreceptor denervation in the toad
A. W. Smits, N. H. West and W. W. Burggren
Pulmonary hemodynamics and net transcapillary fluid flux (NTFF) were
measured in conscious toads before and following bilateral denervation of
the recurrent laryngeal nerves (rLN), which contain afferents from
baroreceptors located in the pulmocutaneous arteries. Denervation caused an
acute doubling of the arterial-venous pressure gradient across the lung and
a threefold increase in pulmonary blood flow. Calculated pulmonary vascular
resistance fell and remained below control values through the period of
experimentation. NTFF increased by an order of magnitude (0.74-7.77 ml X
kg-1 X min-1), as filtration increased in response to the hemodynamic
changes caused by rLN denervation. There was a better correlation between
NTFF and pulmonary blood flow than between NTFF and pulmonary driving
pressure. Our results support the view that tonic neural input from
pulmocutaneous baroreceptors protects the anuran lung from edema by
restraining pulmonary driving pressure and blood flow and perhaps by
reflexly maintaining vascular tone in the extrinsic pulmonary artery,
therefore tending to increase the pre-to-postpulmonary capillary resistance
ratio and biasing the Starling relationship in the pulmonary capillaries
against filtration.
