title: High-affinity binding sites for [3H] verapamil in cardiac membranes.
abstract: The calcium channel blocker [3H]verapamil showed specific binding of high affinity (equilibrium dissociation constant, KD, of 4.25 nM) and low density (maximal number of binding sites, Bmax, 50 fmol/mg protein) in frog heart membranes. Nitrendipine, a new calcium channel blocker, had a potency comparable to verapamil in the inhibition of [3H]verapamil binding. Concentrations of Ca2+ in the medium exceeding 3 mM decreased [3H]verapamil binding. These findings are consistent with the concept that high-affinity binding sites for calcium channel blockers are associated with sarcolemmal calcium channels.
mesh_terms: D000818:Animals; D001001:Anura; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008566:Membranes / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D014700:Verapamil / Q000378:metabolism*
chemical_list: D014700:Verapamil; D002118:Calcium