Alterations in pulmonary artery tone during repeated episodes of
hypoxia.
Mehta, B. C. Yang J. L.
Departments of Medicine, University of Florida College of Medicine
and the VA Medical Center, Gainesville, Florida
APStracts 2:0062L, 1995.
To examine the basis of pulmonary constriction during chronic hypoxia,
rat pulmonary artery rings were precontracted and exposed to multiple
episodes of hypoxia. First hypoxic episode resulted in a transient
contraction, followed by potent relaxation, and then a slow sustained
contraction. Repeated hypoxic exposure resulted in stronger initial
contraction and attenuated relaxation. Prolongation of normoxic
interval between hypoxic episodes reversed the attenuation of hypoxic
relaxation. Pulmonary artery rings that were de-endothelialized or
treated with the nitric oxide synthesis inhibitor Nw-nitro-L-arginine
methyl ester or oxyhemoglobin displayed only hypoxic relaxation
without initial or late contractions, and no attenuation of
relaxation during repeated hypoxia. Pretreatment of rings with
indomethacin, or adenosine or endothelin receptor antagonists had no
effect on the hypoxia-mediated alterations. Thus repetitive exposure
to hypoxia results in an increase in initial contraction and a
decrease in relaxation of pulmonary artery rings. Frequency of
hypoxic episodes and endothelial integrity determine pulmonary tone
during repeated hypoxia. However, cyclooxygenase products, adenosine
or endothelin do not play a role in hypoxia-mediated changes in rat
pulmonary artery tone.
Received 9 January 1995; accepted in final form 17 April 1995.
APS Manuscript Number L004-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 April 1995.