Beta adrenoreceptors in the rabbit bladder detrusor muscle

GF Anderson and BH Marks

This study examines the beta adrenergic receptors of the rabbit detrusor smooth muscle, employing [125I]iodocyanopindolol (ICYP) as a ligand for the binding of beta adrenergic receptors. Saturation binding experiments on the isolated membrane fraction yielded a KD for ICYP of 14.7 pM and a maximum binding of 147.6 fmol/mg of protein. Displacement of labeled ICYP by a series of beta adrenergic agents yielded the following KD values for the combined high and low affinity binding sites: I-propranolol, 0.76 nM; ICI 118,551, 1.7 nM; zinterol, 38.0 nM; metoprolol, 3.5 microM; and practolol, 61.4 microM. When these displacement experimental results were compared to KD values from other reported binding studies with ICYP for beta adrenoreceptors, both the order of potency and the KD values indicated primarily beta-2 adrenergic receptor subtypes. Computer program Scatfit analysis of the displacement curves indicated a single slope and affinity constant for all five beta adrenergic agents. Hofstee plots for zinterol, ICI 118,551 and metoprolol, however, were not linear and indicated that minor populations of beta-1 adrenoreceptors were also present as both high and low affinity binding sites could be defined. It is concluded that the primary receptor population is beta-2 and that this tissue is heterogenous with a small population of beta-1 adrenoreceptors representing approximately 13 to 23% of the total beta adrenoreceptor population.

Volume 228, Issue 2, pp. 283-286, 02/01/1984
Copyright © 1984 by American Society for Pharmacology and Experimental Therapeutics

This article has been cited by other articles:

				H. Takeda, Y. Yamazaki, M. Akahane, Y. Igawa, Y. Ajisawa, and O. Nishizawa Role of the beta 3-Adrenoceptor in Urine Storage in the Rat: Comparison between the Selective beta 3-Adrenoceptor Agonist, CL316,243, and Various Smooth Muscle Relaxants J. Pharmacol. Exp. Ther., June 1, 2000; 293(3): 939 - 945. [Abstract] [Full Text]