Extracellular site for econazole‐mediated block of Ca2+ release‐activated Ca2+ current (Icrac) in T lymphocytes

• Published in: British journal of pharmacology 1996-10, Vol.119 (4), p.647-654
• Main Authors: Christian, Edward P., Spence, Katherine T., Togo, James A., Dargis, Pauline G., Warawa, Edward
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Calcium - metabolism; Calcium Channel Blockers - pharmacology; Calcium current; calcium release‐activated calcium current; cytochrome P‐450; depletion‐activated calcium current; econazole; Econazole - analogs & derivatives; Econazole - pharmacology; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Humans; Immunobiology; Jurkat cell; Jurkat Cells; Lymphoid cells: ontogeny, maturation, markers, receptors, circulation and recirculation; Microdialysis; T lymphocyte; T-Lymphocytes - drug effects; T-Lymphocytes - metabolism
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1111/j.1476-5381.1996.tb15722.x

1 Standard whole cell patch clamp recording techniques were used to study the pharmacological characteristics and site of econazole‐mediated inhibition of calcium release‐activated calcium current (Icrac) in the human leukaemic T cell line, Jurkat. 2 Extracellularly applied econazole blocked Icrac in a concentration‐dependent manner (IC50 ≅ 14 μm). Block developed over a relatively slow timecourse of 30–60 s (10 μm), and only partially reversed over minutes. 3 Econazole dialysed from the pipette into the cytosol at concentrations ranging from 0.1 to 30 μm did not reduce Icrac, or quantitatively affect Icrac block by extracellularly applied econazole. 4 A less lipophilic quaternary iodide derivative of econazole was synthesized to retard absorption through the cell membrane. When applied extracellularly, this compound blocked Icrac in a concentration‐dependent manner with onset kinetics comparable to econazole. 5 Results with intracellularly dialysed econazole and the quaternary econazole derivative provide convergent evidence that econazole blocks Icrac via an extracellular interaction. 6 The inability of intracellularly applied econazole to inhibit Icrac argues against the notion that econazole inhibits capacitative Ca2+ entry pathways secondary to its known inhibitory effects on cytochrome P‐450.