title: [3H]nitrendipine-labeled calcium channels discriminate inorganic calcium agonists and antagonists.
abstract: [3H]Nitrendipine binds with high affinity to brain membranes with a drug specificity indicating association with sites mediating the pharmacologic actions of dihydropyridine slow-calcium-channel antagonist drugs. In brain membranes, [3H]nitrendipine binding is absolutely dependent on the presence of calcium ions. Interactions of cation with [3H]nitrendipine binding sites correlate with their physiologic actions at voltage-dependent calcium channels. Ions such as strontium and barium, which mimic calcium physiologically, share the action of calcium in enhancing [3H]nitrendipine binding. Ions such as lanthanum an cobalt, which block the effects of calcium, can inhibit [3H]nitrendipine binding and block the stimulating actions of calcium. The ability to monitor the influence of ions on an agonist-antagonist continuum at [3H]nitrendipine binding sites provides a molecular probe to explore the regulation of cellular function by calcium and other cations.
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D001931:Brain Mapping; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002413:Cations, Divalent / Q000378:metabolism; D006168:Guinea Pigs; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D009543:Nifedipine / Q000031:analogs & derivatives / Q000378:metabolism*; D009568:Nitrendipine; D011725:Pyridines / Q000378:metabolism*; D051381:Rats; D014018:Tissue Distribution
chemical_list: D002413:Cations, Divalent; D007473:Ion Channels; D011725:Pyridines; D009568:Nitrendipine; D009543:Nifedipine; D002118:Calcium