Lung -Adrenoceptors in Pulmonary Hypertension* A Study of Biopsy Specimens in Children with Congenital Heart Disease

Characteristics of 3-adrenoceptors were analyzed using radioligand-binding techniques with H-dihydroalprenolol in lung specimens from 11 children with pulmonary hypertension (median age, three years) undergoing surgical repair ofeongenital heart defects and four pediatric control subjects (median age, five years) undergoing thoracotomy for removal of neoplasms or cysts. Scatchard analysis of 3H-DIIA binding to lung membranes showed similar values ofthe dissociation constant in both groups (Kd0.72±0.22 nM in patients vs 1.22±0.22 nM in controls; pNS). The receptor density was significantly increased in patients in comparison with controls, with respective values of 164 ± 19 and 95 ± 13 fmol/mg of protein (p<O.OZS), and correlated directly with mean pulmonary arterial pressure (r0.82; p<O.0005). No significant relationship was observed between receptor number and pulmonary arterial medial thickness. Thus, the increase in receptor density in these patients may be related to adaptative changes in cells other than vascular smooth muscle. (Chest 1991; 99:637-41)