title: Role of [Ca2+]i in lethal oxidative injury in rat cultured inner medullary collecting duct cells.
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 [Ca2+]i increase and afforded significant protection against cellular injury following exposure to TBHP-induced 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.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D007679:Kidney Medulla / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D010545:Peroxides / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013050:Spectrometry, Fluorescence; D014700:Verapamil / Q000494:pharmacology; D020122:tert-Butylhydroperoxide
chemical_list: D002121:Calcium Channel Blockers; D010545:Peroxides; D020122:tert-Butylhydroperoxide; D014700:Verapamil; D002118:Calcium