Prostaglandin e2 and i2 cause greater relaxations in pulmonary
veins than in arteries of newborn lambs.
Gao, Yuansheng, Haiyan Zhou, Basil O. Ibe, and J. Usha Raj.
Department of Pediatrics, Harbor-UCLA Medical Center, University of
California, Los Angeles, School of Medicine, Torrance, CA 90509
APStracts 3:0391A, 1996.
Prostaglandin E2 (PGE2) and I2 (PGI2) are important vasoactive
mediators in pulmonary vessels. The present study was designed to
determined whether or not the responses of pulmonary arteries to
these prostanoids are different from those of veins in newborn lambs.
Fourth generation pulmonary arterial and venous rings without
endothelium were suspended in organ chambers filled with modified
Krebs-Ringer bicarbonate solution (95% O2 -5% CO2, 37oC) and their
isometric force was measured. During contraction with endothelin-1 or
U46619 (indomethacin was present to eliminate the possible
involvement of endogenous cyclooxygenase products), PGE2, PGI2 and
carbacyclin (a stable analogue of PGI2) induced greater relaxations
in veins than in arteries. In both vessel types, relaxations induced
by PGE2 were larger than those by PGI2 or carbacyclin. Forskolin, an
activator of adenylate cyclase, also induced greater relaxation of
veins than those of arteries. Relaxation induced by 8-Bromo-cAMP, an
analogue of cAMP, was comparable in both vessel types.
Radioimmunoassay revealed that the basal and calcium ionophore
A23187-induced releases of PGE2 or 6-keto-PGF1[alpha] (the stable
breakdown product of PGI2) were similar between arteries and veins.
Measurement of cAMP (in the presence of isobutylmethylxanthine)
showed PGE2 and forskolin induced greater increase in cAMP in veins
than in arteries. Our results demonstrate that PGE2 and PGI2 are more
potent vasodilators in pulmonary veins than in arteries in newborn
lambs. A difference in the activity of adenylate cyclase may
contribute to the differential responses to PGE2 and PGI2 between
pulmonary arteries and veins. Furthermore, PGE2 appears play an more
important role than PGI2 in modulating pulmonary vascular tone of
newborn lambs.
Received 10 October 1995; accepted in final form 12 August 1996.
APS Manuscript Number A1097-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996