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||The Effect of Capsazepine and Nonylphenol on Calcium Signaling and Viability in MDCK Renal Tubular Cells|
|Date of Defense
||The effect of capsazepine and nonylphenol on cytosolic free Ca2+ concentrations ([Ca2+]i) in MDCK renal tubular cells is unclear. This study explored whether capsazepine and nonylphenol changed basal [Ca2+]i levels in suspended MDCK cells by using fura-2 as a Ca2+-selective fluorescent dye. Capsazepine at concentrations between 10 and 200 microM increased [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was reduced partially by 40% after removing extracellular Ca2+. Capsazepine induced Mn2+ quench of fura-2 fluorescence, indirectly implicating Ca2+ entry. Capsazepine-induced Ca2+ influx was not changed by L-type Ca2+ entry inhibitors and protein kinase C modulators [phorbol 12-myristate 13-acetate (PMA) and GF109203X]. In Ca2+-free medium, 100microM 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.|
Nonylphenol also increased [Ca2+]i in a concentration- dependent manner like capsazepine does. Similar response in [Ca2+]i rise can be found by inhibition of phospholipase C and using thapsigargin. Different from capasazpine, the [Ca2+]i rise was inhibited by PMA. At concentrations between 5 and 100microM, nonylphenol killed cells in a concentration-dependent manner.
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. Nonylphenol induced [Ca2+]i increase in MDCK cells via evoking Ca2+ entry through protein kinase C-regulated Ca2+ channels, and releasing Ca2+ from endoplasmic reticulum and other cellular storage in a phospholipase C-independent manner.
||Ying-Huei Lee - chair|
Tony Wu - co-chair
Chen-fu Shaw - co-chair
Chung-ren Jan - advisor
David Chao - advisor
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