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 micrograms 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.