Mapping of beta-adrenergic receptors in rat lung: effect of isoproterenol.

beta-Adrenergic receptors were mapped in the rat lung using a light microscopic technique that identifies binding sites for 3H-labeled dihydroalprenolol in intact slide-mounted tissue sections, which were also used for biochemical analysis of ligand binding. Grain density measurements were combined with morphometric data. These results indicate that, although over 97% of the specific binding is to cells of alveolar walls, beta-adrenergic receptors are present and can be quantified in tissues that represent a small fraction of total lung mass, such as bronchial epithelium and smooth muscle of bronchial walls and pulmonary vessels. Repeated administration of isoproterenol decreased the receptor number, as determined biochemically and from grain density measurements, in all anatomic regions studied, but did not alter the distribution of binding.