Binding of beta(1)-adrenoceptor antagonist [H-3]CGP 26505 in rat cerebral cortex and sinus atrial node

Specific beta(1)-adrenoceptors antagonist [H-3]CGP 26505 binding was characterized in rat cerebral cortex and heart sinus atrial node. In both tissues [H-3]CGP 26505 binding was maximal at 25 degrees C, it was specific, saturable and protein concentration dependent. Scatchard analysis of saturation isotherms of specific [H-3]CGP 26505 binding in cerebral cortex showed that [H-3]CGP 26505 binds a single class of high affinity sites with a dissociation constant (K-D) of 1 +/- 0.3 nM and a maximal number of binding sites (B-max) of 40 +/- 2 fmol/mg of protein. In sinus atrial node, [H-3]-CGP 26505 binds a single class of high affinity sites (K-D = 1.9 +/- 0.4 nM, B-max = 28 +/- 2 fmol/mg of protein).