To investigate the expression and distribution of endothelin receptors in pulmonary circulation in children with congenital left-to-right shunts and to explore their correlations with histopathological changes in pulmonary vasculature.

23 children with congenital left-to-right shunts were divided into 3 groups according to the echocardiographic Q_p/Q_s and RPEP/VTI(right ventricular pre-ejection period/velocity time integral which may characterize the difference in pulmonary resistance).Integral optical density(IOD)of receptors in pulmonary circulation was measured by immunohistochemical stain of receptors.Stereologic and histopathologic methods were used to measure parameters including PCNA, WT%(percent wall thickness)and density of vasculature and the distribution of α-actin positive cells, so as to assess the vascular remodeling of pulmonary circulation.

Expression of two endothelin receptor subtypes were both higher on small pulmonary arteries in cases than in control cases(P<0.01).Expression of both subtypes correlated basically well with the stereologic and pathological parameters of remodeling of small pulmonary arteries.

Stereologic assay is more sensitive than Health-Edwards criteria in evaluating the vascular remodeling in early pulmonary hypertension induced by congenital left-to-right shunts.The changes of ET receptor expression in small PA implicate that important role of ET in pulmonary hypertension may also correlate with the up-modulating of ET receptors due to change in flow dynamics.