Selectivity of Bunitrolol for β1- and β2-Adrenergic Receptors and 5HT1B-receptors: Assessment by Biphasic Scatchard Plots and Biphasic Displacement Curve Analysis with 125I-Iodocyanopindolol and 3H-CGP12177

摘要

References(20) Cited-By(3) The preference by bunitrolol for β1 and β2-adrenoceptors of the rat brain, heart and/or lung was assessed by the radioligand binding assay method with 125I-iodocyanopindolol (125I-ICYP) or 3H-CGP12177. Scatchard plots of 125I-ICYP binding in the presence of bunitrolol were found to be non-linear. The inhibition constants (Kj) of bunitrolol for high (β2-) and low affinity sites (β1-) were: 0.42±0.16 nM for β1 and 3.55±1.61 nM for β2 (β1 β2), respectively. Displacement experiments conducted with the preparations of the rat brain using 125I-ICYP or with the preparations of the rat heart using 3H-CGP12177 yielded Kj values for bunitrolol of 0.53±0.20 (β1) and 2.37±0.78 (β2) nM for 125I-ICYP binding and 2.01±0.38 (β1) and 12.67±6.54 (β2) nM for 3H-CGP12177 binding. In addition, the Kj value for 5HT1B-receptors assessed in displacement experiments conducted with 125I-ICYP in the presence of 30 μMI-metoprolol in the rat brain was 10.54±5.92 nM. Thus, bunitrolol is a β1-selective antagonist.