title: Clotrimazole inhibits the recombinant human cardiac L-type Ca2+ channel alpha 1C subunit.
abstract: 1. Clotrimazole (CLT) is an antimycotic agent with a potential role in the treatment of cancer. Whole-cell patch clamp recordings and Fura-2 AM fluorescence measurements were used to investigate the inhibition by CLT of recombinant human cardiac L-type Ca2+ channel alpha 1C subunits, stably expressed in human embryonic kidney (HEK 293) cells. 2. CLT (100 nmol l-1 to 25 mumol l-1) reduced Ca2+ channel currents in a concentration-dependent manner. Inhibition was neither use- or voltage-dependent. The effects of CLT were rapid and maximal effects were attained within 3 min. Application of CLT also caused an acceleration of apparent Ca2+ channel current inactivation. 3. Basal current density and the degree of inhibition due to CLT were not significantly altered by pretreating cells with 3 mmol l-1 1-aminobenzotriazole for 1 h, or by dialysing cells for 10 min with 2 mmol l-1 alpha-napthoflavone via the patch pipette, suggesting that the inhibitory action of CLT was not due to inhibition of cytochrome P-450. 4. CLT (10 mumol l-1) did not influence [Ca2+]i, as determined by Fura-2 AM fluorescence measurements. 5. Dialysing cells for 10 min with the non-specific serine/threonine kinase inhibitor H-7 (10 mumol l-1) was without effect on basal current density or on the inhibitory response to 10 mumol l-1 CLT, indicating that CLT is not acting via an indirect effect on these kinases. 6. These data suggest that CLT exerts a direct blocking effect on the alpha 1C subunit at therapeutic concentrations. This effect may explain the abbreviation of the action potential duration by CLT observed in cardiac myocytes.
authors.affiliation: Institute for Cardiovascular Research, University of Leeds. cvsimt@leeds.ac.uk
authors.forename: I M
authors.initials: IM
authors.lastname: Fearon
authors.forename: S G
authors.initials: SG
authors.lastname: Ball
authors.forename: C
authors.initials: C
authors.lastname: Peers
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism*; D002460:Cell Line; D003022:Clotrimazole / Q000494:pharmacology*; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis
chemical_list: D000935:Antifungal Agents; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D065607:Cytochrome P-450 Enzyme Inhibitors; D011994:Recombinant Proteins; D003577:Cytochrome P-450 Enzyme System; D003022:Clotrimazole; D002118:Calcium