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Endothelin receptor expression in human lungs of newborns with congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a major cause of refractory respiratory failure in the neonatal period and is characterized by persistent pulmonary hypertension of the newborn (PPHN) and pulmonary hypoplasia. Endothelin‐1 (ET‐1) dysregulation may play a significant role in the pathophysiology of PPHN and ET‐1 acts through binding to type A (ETA) and type B (ETB) receptors. Therefore, ETA and ETB receptor protein expression was studied using immunohistochemistry in 10 lung specimens obtained from newborns with CDH, and 4 normal lung specimens, in order to explore whether dysregulation of ETA and ETB expression contributes to PPHN. ETA and ETB mRNAs were then quantified using real‐time RT‐PCR in laser‐microdissected pulmonary resistive arteries. In the lungs of newborns with CDH, immunohistochemistry of both ETA and ETB receptors demonstrated over‐expression in the thickened media of pulmonary arteries. Using laser microdissection and real‐time RT‐PCR, higher levels of ETA and ETB mRNA were found in CDH pulmonary arteries than in controls: this increase was more pronounced for ETA mRNA. This study provides the first demonstration of ET‐1 receptor dysregulation in association with structural alteration of pulmonary arteries in newborns with CDH and PPHN. This dysregulation preferentially affects the ETA receptor. These results suggest that dysregulation of ET‐1 receptors may contribute to PPHN associated with CDH. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.