Am. J. Respir. Crit. Care Med., Vol 153, No. 1, Jan 1996, 211-217.
Modulation of hypoxic pulmonary vasoconstriction by antioxidant enzymes in red blood cells
K Yamaguchi, K Asano, T Takasugi, M Mori, H Fujita, Y Oyamada, K Suzuki, A Miyata, T Aoki and Y Suzuki
Department of Medicine, School of Medicine, Keio University, Tokyo, Japan.
To determine whether antioxidant mechanisms within red blood cells (RBCs)
significantly contribute to preserving hypoxic pulmonary vasoconstriction
(HPV) in both the absence and the presence of oxidative stress, we
investigated HPV changes in isolated rabbit lungs perfused with solutions
containing RBCs treated with various inhibitors of superoxide dismutase
(SOD), anion channels, catalase (CAT), or glutathione peroxidase (GSH-Px).
Perfusion was maintained at a constant flow rate of 70 ml/min, and lung
temperature at 37 to 38 degrees C. Hematocrit was adjusted to 7%. In the
absence of overt oxidative stress, HPV was significantly enhanced in the
perfusate containing control RBCs (untreated RBCs) as compared with that in
Krebs-Henseleit buffer. Inhibition of SOD, CAT, and GSH-Px within RBCs, as
well as anion channels located on the RBC membrane, had little influence on
HPV. Neither exogenous SOD nor CAT altered HPV. In the presence of high
levels of reactive oxygen species (ROS), generated by addition of xanthine
(100 microM) and xanthine oxidase (10 mU/ml) to the reservoir, HPV was
considerably suppressed in the perfusate containing only buffer but was
restored in the perfusate with control RBCs. Inhibition of CAT or GSH-Px in
RBCs preserved the HPV, whereas inhibition of SOD or anion channels failed
to preserve HPV obtained during exposure to high ROS levels. Addition of
exogenous SOD, but not CAT, to the perfusate containing RBCs in which
endogenous SOD had been inhibited restored HPV under high ROS conditions.
In conclusion, (1) although RBCs augment HPV in the absence of ROS, this
finding is not attributable to the antioxidants in RBCs. (2) RBCs restore
HPV upon exposure to high ROS. This finding may well be explained by
antioxidant mechanisms operating within RBCs, especially those of
endogenous SOD.
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Copyright © 1996 American Thoracic Society
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