Leukotriene inhibition prevents and reverses hypoxic pulmonary vasoconstriction in newborn lambs

The effects of the leukotriene antagonist FPL 57231 on the circulation were studied in spontaneously breathing normoxic and hypoxic newborn lambs in order to evaluate the role of leukotrienes in the perinatal control of hypoxic pulmonary vasoconstriction. Hypoxia produced a 58% increase in pulmonary arterial pressure (p less than 0.05) and a 37% increase in pulmonary vascular resistance (p less than 0.05). Hypoxic pulmonary vasoconstriction was abolished by the prior infusion of FPL 57231. Pulmonary arterial pressure increased by only 8% and pulmonary vascular resistance decreased by 10% from normoxia. The infusion of FPL 57231 during hypoxia-induced pulmonary vasoconstriction reversed the increase in pulmonary arterial pressure (p less than 0.05) and pulmonary vascular resistance (p less than 0.05). The hypoxia-induced increase in cardiac output was maintained during the infusion of FPL 57231. Leukotrienes may play a significant role in the mediation of hypoxic pulmonary vasoconstriction. Leukotriene inhibition with FPL 57231 may be useful in the management of infants with persistent pulmonary hypertension syndrome.