Abstract :
[en] The 8-epi-PGF2α is a marker of oxidative stress which is increased in lungs of asthmatic
humans and heaves-susceptible horses. 8-Epi-PGF2α has also been demonstrated to be an in vitro and in vivo bronchoconstrictor in humans and rodents. We hypothesised that inhaled 8-epi-PGF2α was a bronchoconstrictor in healthy and heaves-susceptible horses in clinical remission. The effect on ventilatory mechanics of nebulised 8-epi-PGF2α was compared to that of PGF2α and U46619, a thromboxane A2 agonist. Pulmonary resistance (RL) and dynamic compliance (Cdyn) were assessed in six healthy horses and in six heaves-susceptible horses in clinical remission before (baseline) and immediately after a single inhalation challenge of 1 mg 8-epi-PGF2α, PGF2α, or U46619 and placebo. RL and Cdyn were unchanged after inhalation of 8-epi-PGF2α in healthy horses. In heaves-susceptible horses, 8-epi-PGF2α induced a significant increase of RL and a significant decrease of Cdyn when compared to baseline values. Differences between RL and Cdyn values after 8-epi-PGF2α inhalation and those of placebo inhalation were not significant. Differences with healthy horses were not significant. PGF2α and U46619 induced a significant bronchoconstriction in healthy (RL and Cdyn, versus baseline) and heaves-susceptible horses (RL and Cdyn, versus baseline and placebo). The RL increase in heaves-susceptible horses after PGF2α inhalation was significantly higher than that in healthy horses. Our results suggest that 8-epi-PGF2α is not a bronchoconstrictor in healthy horses, and a bronchoconstrictor far less efficient than PGF2α and U46619 at the same dose in heaves-susceptible horses
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