Autoradiographic Localization of Beta-Adrenoceptors in Asthmatic Human Lung

The autoradiographic distribution and density of beta-adrenoceptors in human non-diseased and asthmatic bronchi were investigated using [125I]iodocyanopindolol (I-CYP). Analysis of the effects of the beta-adrenoceptor antagonists on I-CYP binding demonstrated that betaxolol (20 nM, beta1-selective) had no significant effect on specific grain density in either nonasthmatic or asthmatic human bronchus, whereas ICI-118551 (20 nM, beta2-selective) inhibited I-CYP binding by 85 ± 9% and 89 ± 3%, respectively. Thus, homogeneous populations of beta2-adrenoceptors existed in bronchi from both sources. Large populations of beta-adrenoceptors were localized to the bronchial epithelium, submucosal glands, and airway smooth muscle. Asthmatic bronchial tissue featured epithelial damage with exfoliated cells associated with luminal mucus plugs. A thickened basement membrane and airway smooth muscle hyperplasia were also evident. High levels of specific I-CYP binding were also detected over asthmatic bronchial smooth mu...