Role of [Ca2+]i in lethal oxidative injury in rat cultured inner medullary collecting duct cells |
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Authors: | Yutaka Kuroda Katsuji Takeda Kaoru Tabei Masatoshi Kuroki Toshio Yagimuma Tomoko Ohara Yasushi Asano |
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Affiliation: | (1) Department of Internal Medicine, Omiya Medical Center, Jichi Medical School, 330 Saitama, Japan;(2) Department of Nephrology, Jichi Medical School, 329-04 Tochigi, Japan |
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Abstract: | Reactive oxygen metabolites have been implicated in the pathogenesis of toxic, ischaemic and immunologically mediated renal injury. An increase in the cytosolic free Ca2+ concentration ([Ca2+]i) has been proposed as a mechanism of oxidative stress-induced cell injury. We used a fluorescence spectrometer and a fluorescence probe to measure the [Ca2+]i and viability of rat primary cultured inner medullary collecting duct (IMCD) cells during oxidative stress induced by 5 mM tert-butyl hydroperoxide (TBHP). Initially, this oxidative stress evoked a small increase in [Ca2+]i which was followed by a slower sustained increase from the resting level of 170.8±38.8 nM to 1490.5±301.7 nM after 60 min, and this preceded the loss of plasma membrane integrity, measured by the propidium iodide fluorescence method. The elimination of extracellular Ca2+ from the culture medium prevented the TBHP-induced [Ca2+]i increase and improved cell viability. Restoration of extracellular Ca2+ resulted in an immediate and large increase in [Ca2+]i and extensive cell death. Verapamil, a Ca2+ channel blocker, inhibited the [Ca+]i increase and afforded significant protection against cellular injury following exposure to TBHPinduced oxidative stress. Extracellular acidosis also prevented the increase in [Ca2+]i and cell death caused by this oxidative stress. These results are consistent with the hypothesis that oxidative stress-induced IMCD cellular injury may be the result of increased [Ca2+]i caused, in part, by activation of voltage-dependent Ca2+ channels. |
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Keywords: | tert-Butyl hydroperoxide Cytosolic free calcium ion concentration Cell death Acidosis Calcium antagonist Inner medullary collecting duct cell |
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