Effect of capsazepine on [Ca2+]i in MDCK renal tubular cells

The current study explored whether capsazepine changed basal cytosolic free Ca2+ concentrations ([Ca2+]i) levels in suspended Madin Darby canine kidney (MDCK) cells cells by using fura-2 as a Ca2+-selective fluorescent dye. At concentrations of 10–200 µM, capsazepine increased [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was partially reduced by 40% by removing extracellular Ca2+. Capsazepine induced Mn2+ quench of fura-2 fluorescence, indirectly implicating Ca2+ entry. Capsazepine-induced Ca2+ influx was unchanged by L-type Ca2+ entry inhibitors and protein kinase C modulators [phorbol 12-myristate 13-acetate (PMA) and GF109203X]. In Ca2+-free medium, 100 µM capsazepine-induced Ca2+ release was substantially suppressed by pretreatment with thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor). Pretreatment with capsazepine nearly abolished thapsigargin-induced Ca2+ release. Inhibition of phospholipase C with U73122 did not change capsazepine-induced [Ca2+]i rises. Collectively, in MDCK cells, capsazepine induced [Ca2+]i rises by causing phospholipase C-independent Ca2+ release from the endoplasmic reticulum and Ca2+ influx via non-L-type Ca2+ channels. Drug Dev Res 72: 323–329, 2011. © 2010 Wiley-Liss, Inc.