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

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