Segmental pulmonary vascular responses to atp in rat lungs: role of
nitric oxide.
Hakim, Tawfic S., Lara Ferrario, Jeffrey C. Freedman, Robert E.
Carlin, and Enrico M. Camporesi.
Departments of Surgery, Anesthesiology and Physiology, SUNY Health
Science Center, 750 East Adams Street, Syracuse, New York, 13210
APStracts 3:0514A, 1996.
Adenosine triphosphate (ATP) exhibits vascular pressor and depressor
responses in a dose and tone dependent manner. The vascular site of
ATP-induced contraction or dilation has not previously been
characterized. Using the vascular occlusion technique, we
investigated the effects of ATP in isolated rat lungs perfused with
autologous blood (Hct=20%), and described its action during resting
and elevated tone in terms of changes in resistances of the small and
large arteries and veins. During resting tone, ATP (10 M) caused
contraction primarily in the small arteries and to some extent in the
small veins suggesting that P2x purinoceptors are present in these
small vessels. During hypoxia, ATP caused dilation primarily in the
small arteries, suggesting that P2y purinoceptors are predominant in
small arteries. During U46619-induced contraction, which occurred
evenly throughout the four segments, ATP caused dilation in the large
arteries and veins but not in the small arteries and veins. After
treatment with NitroW-L-arginine to inhibit nitric oxide synthesis,
ATP-induced contraction was potentiated, and its dilatory effects
during hypoxia were attenuated. The action of ATP was independent of
prostanoids since its constrictor and dilatory responses were not
affected significantly by indomethacin. In conclusion, the results
indicate that the effects of ATP on the pulmonary vasculature are
primarily due to P2x and P2y purinoceptors in the small arteries.
Contribution of these purinoceptors in other vessels to changes in
total vascular resistance in rat lung was minor.
Received 3 May 1996; accepted in final form 1 November 1996.
APS Manuscript Number A428-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996