Journal of Applied Physiology
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J Appl Physiol 70: 740-747, 1991;
8750-7587/91 $5.00
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Journal of Applied Physiology, Vol 70, Issue 2 740-747, Copyright © 1991 by American Physiological Society

ARTICLES

Hyperoxia prevents hypoxia-induced bronchial hyperreactivity via a cyclooxygenase-independent mechanism

J. D'Brot and T. Ahmed
Division of Pulmonary Disease, University of Miami School of Medicine, Mount Sinai Medical Center, Miami Beach, Florida 33140.

We tested the hypothesis that prior exposure to alveolar hyperoxia prevents the hypoxia-induced enhancement of bronchial reactivity, possibly via a cyclooxygenase-dependent mechanism. In 15 sheep, specific lung resistance (sRL) was measured before and after 30 min of exposure to either air or a hypoxic gas mixture (13% O2). The sheep then inhaled 50 breaths of aerosolized 5% histamine solution (n = 9) or 10 breaths of 2.5% carbachol solution (n = 9), and measurements of sRL were repeated. On subsequent days the above protocols were repeated after a 30-min exposure to hyperoxia (O2 greater than or equal to 95%), without or after pretreatment with indomethacin (2 mg/kg). After air-sham exposure, carbachol and histamine increased mean sRL to 370 +/- 40 (SE) and 309 +/- 65% of baseline, respectively. Exposure to the hypoxic gas mixture had no effect on baseline sRL but enhanced the airway responsiveness to carbachol and histamine; mean sRL increased to 740 +/- 104 and 544 +/- 76% of baseline, respectively (P less than 0.05). Prior 30-min exposure to hyperoxia prevented the hypoxia-induced enhancement of bronchial reactivity to carbachol (sRL = 416 +/- 66% of baseline) and histamine (sRL = 292 +/- 41% of baseline) without affecting the airway responsiveness to these agents after air. Pretreatment with indomethacin did not reverse the protective effects of hyperoxia or the hypoxia-induced enhancement of bronchial reactivity. We conclude that 1) prior exposure to alveolar hyperoxia prevents the hypoxia-induced enhancement of bronchial reactivity and 2) neither the protective effects of hyperoxia nor the hypoxia-induced enhancement of bronchial reactivity is mediated via a cyclooxygenase-dependent mechanism.


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H. Saito, M. Nishimura, H. Shinano, F. Sato, K. Miyamoto, and Y. Kawakami
Effect of Mild Hypoxia on Airway Responsiveness to Methacholine in Subjects With Airway Hyperresponsiveness*
Chest, December 1, 1999; 116(6): 1653 - 1658.
[Abstract] [Full Text] [PDF]


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