Binding of the hydrophilic β-adrenergic antagonist [3H]CGP-12177 to cardiac tissue slices: characterization and ontogenetic studies in dogs

Publisher Website
Google Scholar
Abstract
A new technique was developed to characterize the binding of a hydrophilic β-adrenergic antagonist, [3H]CGP-12177, to 1-mm thick slices of canine cardiac tissue. This technique was used to quantify the density (Bmax) and the affinity (Kd) of these receptors in the right ventricular conus (RVC) and the left ventricle (LV) at day 1 to 6 weeks of age, and in the adult. Binding was found to be reversible, saturable, stereospecific, of high affinity, and thermolabile. There was an increase in the density of β-adrenergic receptors between day 1 (Bmax = 2.2 ± 0.3 fmol/mg tissue in RVC and 2.9 ± 0.8 fmol/mg tissue in the LV) and 2 weeks of age postnatally, after which it remained constant until 6 weeks of age (Bmax = 7.5 ± 0.4 and 6.8 ± 0.9 fmol/mg tissue in RVC and LV, respectively); however, by 6 weeks of age it had not reached adult levels (10.3 ± 1.0 fmol/mg tissue). The affinity of these receptors did not change between early neonatal life (Kd = 1.3 ± 0.4 nM) and adulthood (Kd = 1.4 ± 0.2 nM). The density of β-adrenergic receptors in the RVC was similar to that in the LV. This new method of quantifying β-adrenergic receptors in cardiac tissue is simple and fast, and requires minimal tissue handling. It proved to be useful in studying the development of cardiac β-adrenergic receptors with age.