Airway beta-adrenoceptor number in cystic fibrosis and asthma

1. Maximal binding capacity (Bmax) and the dissociation constant (KD) for the beta-adrenoceptor antagonist 125I-cyanopindol were estimated in membrane preparations of hilar, lobar/main bronchi (level I) and peripheral lung (level II) of grossly normal lungs resected for bronchial carcinoma. The tissue distribution of 125I-cyanopindol-binding sites was assessed by autoradiography of complementary cryostat sections. The data obtained from the resections for carcinoma and bronchiectasis were used as disease controls for comparison with those obtained from patients with cystic fibrosis and asthma. 2. In carcinoma controls, mean Bmax values (+/- SEM) for airway levels I and II were 89 +/- 4 and 133 +/- 6 fmol/mg of protein, respectively (P less than 0.01). The corresponding KD values at each airway level were similar, i.e. 29 +/- 2 and 33 +/- 1 pmol/l, respectively. Autoradiography revealed that there was dense labelling of bronchial and bronchiolar epithelium and most strikingly of the alveolar wall. 3. Compared with carcinoma controls, mean Bmax values in cystic fibrosis were significantly reduced in membrane preparations of both airway levels I and II (P less than 0.01). Autoradiography showed the reduction was most apparent in alveolar wall and bronchial epithelium. 4. There was a tendency to reduction of Bmax in membrane preparations from patients with bronchiectasis at airway level I, but this failed to reach statistical significance. Autoradiography demonstrated that the density of labelling was significantly reduced in bronchial epithelium and bronchial smooth muscle as compared with carcinoma controls (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)