title: Molecular pharmacology of human Cav3.2 T-type Ca2+ channels: block by antihypertensives, antiarrhythmics, and their analogs.
abstract: Antihypertensive drugs of the "calcium channel blocker" or "calcium antagonist" class have been used to establish the physiological role of L-type Ca(2+) channels in vascular smooth muscle. In contrast, there has been limited progress on the pharmacology T-type Ca(2+) channels. T-type channels play a role in cardiac pacemaking, aldosterone secretion, and renal hemodynamics, leading to the hypothesis that mixed T- and L-type blockers may have therapeutic advantages over selective L-type blockers. The goal of this study was to identify compounds that block the Ca(v)3.2 T-type channel with high affinity, focusing on two classes of compounds: phenylalkylamines (e.g., mibefradil) and dihydropyridines (e.g., efonidipine). Compounds were tested using a validated Ca(2+) influx assay into a cell line expressing recombinant Ca(v)3.2 channels. This study identified four clinically approved antihypertensive drugs (efonidipine, felodipine, isradipine, and nitrendipine) as potent T-channel blockers (IC(50) < 3 microM). In contrast, other widely prescribed dihydropyridines, such as amlodipine and nifedipine, were 10-fold less potent, making them a more appropriate choice in research studies on the role of L-type currents. In summary, the present results support the notion that many available antihypertensive drugs block a substantial fraction of T-current at therapeutically relevant concentrations, contributing to their mechanism of action.
authors.affiliation: Department of Pharmacology, University of Virginia, Charlottesville, Virginia, USA. eperez@virginia.edu
authors.forename: Edward
authors.initials: E
authors.lastname: Perez-Reyes
authors.forename: Amy L
authors.initials: AL
authors.lastname: Van Deusen
authors.forename: Iuliia
authors.initials: I
authors.lastname: Vitko
mesh_terms: D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D000959:Antihypertensive Agents / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020747:Calcium Channels, T-Type / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D004095:Dihydropyridines / Q000494:pharmacology*; D006801:Humans; D020748:Mibefradil / Q000494:pharmacology; D009596:Nitrophenols / Q000494:pharmacology*; D009943:Organophosphorus Compounds / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
chemical_list: D000889:Anti-Arrhythmia Agents; D000959:Antihypertensive Agents; C479952:CACNA1H protein, human; D002121:Calcium Channel Blockers; D020747:Calcium Channels, T-Type; D004095:Dihydropyridines; D009596:Nitrophenols; D009943:Organophosphorus Compounds; D020748:Mibefradil; C066425:efonidipine; D014700:Verapamil; D002118:Calcium