Kinetic Analysis of Cardiac β-Receptors in Perfused Working Rabbit Hearts

Myocardial adrenergic β-receptors were isolated and partially purified from the nonischemic perfused working rabbit hearts. Using highly radioactive β-receptor antagonist, dihydroalprenolol (DHA), properties of β-receptors were investigated by kinetic equilibrium analysis when the physiological function of the heart appeared to be normal. At the concentration of 10 nM DHA dissociation constant (Kd) was 14.9 nM and there were at least two distinctly different DHA binding sites, based on the analysis of the dissociation rate of DHA-receptor complex. Identification of the two distinctly different DHA binding sites was not obvious from the analysis of Scatchard plot.