Selective distribution of beta- and alpha 1-adrenoceptors in rat lung visualized by autoradiography.

The distribution of beta- and alpha 1-adrenoceptors was studied in rat lung by autoradiography using two ligands: 125-Iodocyanopindolol for beta-adrenoceptors, and 125-Iodo-BE 2254 for alpha 1-adrenoceptors. Beta-adrenoceptors were widely distributed in the lung parenchyma and on the walls of the airways (bronchioles). The epithelium of the bronchioles showed a higher density of beta-adrenoceptors than the smooth muscle. The blood vessels (veins) seemed to have very few beta-adrenoceptors. Alpha 1-adrenoceptors were found in approximately ten fold smaller amounts than beta-adrenoceptors in the lung parenchyma and on the small veins. On the bronchioles, an extremely small number of alpha 1-adrenoceptors was visible.