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Journal of Applied Physiology, Vol 56, Issue 2 370-374, Copyright © 1984 by American Physiological Society
ARTICLES |
B. P. Teisseire and C. D. Soulard
The O2 sensor that triggers hypoxic pulmonary vasoconstriction may be sensitive not only to alveolar hypoxia but also to hypoxia in mixed venous blood. A specific test of the blood contribution would be to lower mixed venous PO2 (PvO2), which can be accomplished by increasing hemoglobin-O2 affinity. When we exchanged transfused rats with cyanate-treated erythrocytes [PO2 at 50% hemoglobin saturation (P50) = 21 Torr] or with Creteil erythrocytes (P50 = 13.1 Torr), we lowered PvO2 from 39 +/- 5 to 25 +/- 4 and to 14 +/- 4 Torr, respectively, without altering arterial blood gases or hemoglobin concentration. Right ventricular systolic pressure increased from 32 +/- 2 to 36 +/- 3 Torr with cyanate erythrocytes and to 44 +/- 5 Torr with Creteil erythrocytes. Cardiac output was unchanged. Control exchange transfusions with normal rat or 2,3-diphosphoglycerate-enriched human erythrocytes had no effect on PvO2 or right ventricular pressure. Alveolar hypoxia plus high O2 affinity blood caused a greater increase in right ventricular systolic pressure than either stimulus alone. We concluded that PvO2 is an important determinant of pulmonary vascular tone in the rat.
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