title: Specific binding of a calcium channel activator, [3H]BAY k 8644, to membranes from cardiac muscle and brain.
abstract: BAY k 8644 is a member of a new class of drugs that directly activates Ca2+ channels. This 1,4-dihydropyridine was found to bind to both high and low affinity sites on rabbit ventricular microsomes and guinea pig brain synaptosomes. The dissociation constant obtained from Scatchard analysis with [3H]BAY k 8644 was 2 to 3 nM for the high affinity binding site, and the estimated maximal number of binding sites was 0.8 and 0.4 pmol/mg protein for heart and brain membranes, respectively, at 15 degrees C. Competition between nitrendipine and [3H]BAY k 8644 indicated a common high affinity binding site for Ca2+ channel activators and antagonists. The results suggest that the 1,4-dihydropyridine Ca2+ channel antagonists do not act as simple channel plugs.
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism*; D009543:Nifedipine / Q000031:analogs & derivatives* / Q000378:metabolism; D009568:Nitrendipine; D011817:Rabbits
chemical_list: D007473:Ion Channels; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009568:Nitrendipine; D009543:Nifedipine; D002118:Calcium