Platelet-activating factor induces relaxation of pulmonary arteries
but contraction of pulmonary veins in the ferret.
Gao, Yuansheng, Haiyan Zhou, and J. Usha Raj.
Department of Pediatrics, Harbor-UCLA Medical Center, University of
California, Los Angeles School of Medicine, Torrance, CA 90509
APStracts 2:0096H, 1995.
The present study was designed to determine whether or not platelet
-activating factor (PAF) has different effects on the responsiveness
of pulmonary arteries and veins. Third order pulmonary arterial and
venous rings of the ferret were suspended in organ chambers filled
with modified Krebs-Ringer bicarbonate solution (95% O2 -5% CO2,
37oC) and their isometric force was measured. Under basal conditions,
PAF had no significant effect on the resting tension of pulmonary
arteries but induced an endothelium-dependent contraction of veins.
The contraction was not affected by BW 755C (inhibitors of
cyclooxygenase and lipoxygenase), BQ-123 (an antagonist of endothelin
ETA receptors), and IRL 1038 (an antagonist of endothelin ETA
receptors). During contraction to prostaglandin F2[alpha]
(PGF2[alpha]), PAF had no significant effect on the response of
pulmonary veins but induced an endothelium-dependent relaxation of
pulmonary arteries. The relaxation was not affected by nitro-D
-arginine but was abolished by nitro-L-arginine. Incubating with PAF
for 30 minutes significantly augmented contractions of veins with
endothelium to PGF2[alpha], but not of veins without endothelium. The
augmentation of contraction pulmonary veins to PGF2[alpha] was not
significantly affected by BW 755C, BQ-123, and IRL 1038. Pretreatment
with PAF had no significant effect on the response of pulmonary veins
to phenylephrine and on the response of arteries to either
PGF2[alpha] or phenylephrine. For both pulmonary arteries and veins,
the effects of PAF were abolished by WEB 2170 (an antagonist of PAF).
Lyso-PAF, an inactive analogue of PAF, had no significant effect on
either basal tone or contractions of pulmonary vessels. These
observations demonstrated that, in the ferret, PAF affected
differently on the response of pulmonary arteries and veins and that
the endothelium plays a critical role in the PAF-induced effects.
Furthermore, the PAF-induced effects appear not to be mediated by
metabolites of arachidonic acid and endothelin.
Received 13 July 1994; accepted in final form 2 March 1995.
APS Manuscript Number H611-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 21 March 1995.