In vitro responses of lung arteries to acute hypoxia after no
synthase blockade or chronic hypoxia.
Teng, Guo. Qi, and Gwenda. R. Barer.
Department of Medicine and Pharmacology, Royal Hallamshire
Hospital, Sheffield S10 2JX, United Kingdom
APStracts 2:0198A, 1995.
Responses to hypoxia of lung arteries (200-350 [mu]m) from control, C
and chronically hypoxic, CH, rats were compared in a myograph before
and after blockade of NO synthase with L-NAME. After precontraction
with PGF2[alpha], hypoxia caused a 4-phase tension change: brief
dilation, transient contraction, prolonged dilation, slow
contraction; (we studied the first 3 phases). In CH rats, the 1st
dilation and 1st contraction were significantly reduced. After L-NAME
the 1st dilation was reduced in C, abolished in CH rats; thus the
first phase is attributable to NO release and is affected by chronic
hypoxia. The 1st contractile phase was significantly reduced by L
-NAME in C but not CH rats, where it was small. Thus NO synthase
inhibition inhibits hypoxic constriction in isolated vessels, whereas
it enhances it in perfused lungs. The 3rd dilator phase was
unaffected by chronic hypoxia; it was increased after L-NAME in CH
rats. Thus, in vitro, responses to hypoxia are multiple; there is a
balance between 2 dilator and 2 constrictor processes.
Received 22 July 1994; accepted in final form 1 May 1995.
APS Manuscript Number A750-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 26 May 1995.