Binding characteristics of 3H-dihydroalprenolol to beta-adrenergic receptors of rat brain: influence of lectins.

The significance of the carbohydrate moieties of the beta-adrenergic receptor molecule in the rat brain was examined using the radioligand binding assay method. Thus, this experiment was designed to assess the effects of lectins, concanavalin A (Con A), Phaseolus vulgaris agglutinin (PHA), and wheat germ agglutinin (WGA) on the affinity of the beta-adrenoceptor. The rat brain was used and the beta-adrenoceptor binding assay was carried out using 3H-dihydroalprenolol as a ligand. Con A and PHA significantly caused an increase in the values of the density of beta-adrenoceptor (Bmax) and a reduction in the values of the dissociation constant (Kd), but significant changes were not observed with WGA. These results strongly suggest that the carbohydrate moieties of the cell surface containing the beta-adrenoceptor molecule may have a crucial role in the drug-receptor interaction, and they imply that the beta-adrenoceptor molecule is a glycoprotein which contains N-linked carbohydrate chains.