CHARACTERIZATION OF BETA-ADRENOCEPTORS ON RAT SKELETAL-MUSCLE CELLS GROWN-INVITRO

The binding properties of an hydrophilic β-adrenergic receptor radioligand, (-)[3H](4-(3-tert-butylamino-2-hydroxypropoxy)-benzimidazolo-2-one); ([3H]CGP-12177), were investigated in rat skeletal muscle cells in culture. The binding of [3H]CGP-12177 at 25° was saturable, reversible and of high affinity (Kd = 1.3 ± 0.3 nM). The maximal number of [3H]CGP-12177 binding sites was 30.6 ± 3.2 fmol/dish (34 ± 3.5 fmol/mg protein). β-Adrenergic agonists and antagonists inhibited [3H]CGP-12177 binding. The competing ligand inhibition binding is a typical one for β2-adrenoceptors. The increase in β-adrenoceptors was independent of cell fusion. Amiodarone (10-5 M) decreased the β-adrenoceptor number in skeletal muscle cells differentiated in vitro by 48%, while the affinity for [3H]CGP-12177 was not affected. © 1990.