Cyclo-oxygenase products mediate hypoxic pulmonary hypertension

Area of Science:

• Neonatal physiology
• Pulmonary medicine
• Vascular pharmacology

Background:

• High-risk infants can develop pulmonary hypertension due to pulmonary vascular bed hyperactivity.
• Hypoxic pulmonary vasoconstriction (HPV) is implicated in this condition, but its mediators are not fully understood.

Purpose of the Study:

• To investigate the role of cyclo-oxygenase derivatives, specifically thromboxane A2 and prostacyclin, in hypoxic pulmonary hypertension.
• To determine if inhibiting thromboxane A2 affects pulmonary hypertension in lambs exposed to hypoxia.

Main Methods:

• Open-chested lambs were ventilated with 13% oxygen.
• Pulmonary and systemic hemodynamics were measured before and after ventilation.
• Lambs were treated with OKY 046, a selective thromboxane inhibitor, in some experiments.
• Levels of thromboxane B2 and 6-keto-prostaglandin F1 alpha were measured.

Main Results:

• Untreated lambs exposed to hypoxia showed a significant increase in pulmonary vascular resistance (PVR) and pulmonary arterial pressure, along with decreased arterial oxygen.
• Thromboxane B2 and 6-keto-prostaglandin F1 alpha levels increased during hypoxia.
• Treatment with OKY 046 prevented the rise in PVR and maintained hemodynamic stability during hypoxic ventilation.

Conclusions:

• Hypoxic pulmonary hypertension in lambs is associated with increased thromboxane A2 and prostacyclin activity.
• Selective inhibition of thromboxane A2 with OKY 046 effectively attenuated hypoxic pulmonary hypertension.
• These findings suggest a significant role for thromboxane A2 in mediating hypoxic pulmonary vasoconstriction.