Prostaglandin D₂ reverses induced pulmonary hypertension in the newborn lamb

We investigated the effects of PGD₂ in six near-term newborn lambs with induced pulmonary hypertension (mean pulmonary arterial pressure equal to mean systemic arterial pressure). In each lamb PGD₂ decreased mean pulmonary arterial pressure, increased pulmonary blood flow, and therefore decreased pulmonary vascular resistance without changing mean systemic arterial pressure. A bolus dose of 20 μg PGD₂ decreased pulmonary arterial pressure by 30%, increased pulmonary blood flow by 45%, and decreased pulmonary vascular resistance by 54%; systemic arterial pressure increased by 4%. At all doses, pulmonary vascular resistance fell further than systemic vascular resistance, the ratio of percent change in pulmonary vascular resistance to percent change in systemic vascular resistance was approximately 2:1. Similar changes occurred with continuous infusions of PGD₂. These effects suggest a role for PGD₂ in the normal regulation of pulmonary vascular resistance and blood flow at birth. In addition, because PGD₂ in these circumstances increases pulmonary blood flow and reduces pulmonary arterial pressure, it may merit further trials in nonhuman primates; it may be an appropriate agent for treating newborn infants with persistent pulmonary hypertension.