Effects of Ca2+ channel blockers on cytosolic Ca2+ levels in neuronal cells under oxidative stimulation induced by t-butyl hydroperoxide

• Main Authors: Cheng-Hsien Lu, 盧成憲
• Other Authors: Chung-Ren Jan
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/44500102090546873294

碩士 === 長庚大學 === 臨床醫學研究所 === 90 === The effect of the oxidant t-butyl hydroperoxide on intracellular free levels of Ca2+ ([Ca2+]i) in PC12 pheochromocytoma cells was examined by using fura-2 as a fluorescent dye. t-Butyl hydroperoxide induced an increase in [Ca2+]i in a concentration-dependent fashion between 50-250 mM with an EC50 of 100 mM. The [Ca2+]i signal consisted of a slow rise and a sustained phase. The response was decreased by 65% by removal of extracellular Ca2+. In Ca2+-free medium, pretreatment with 1 mM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor) abolished 150 mM t-butyl hydroperoxide-induced [Ca2+]i increase, and conversely, pretreatment with t-butyl hydroperoxide abrogated thapsigargin-induced [Ca2+]i increase. The 150 mM t-butyl hydroperoxide-induced [Ca2+]i increase in Ca2+ medium was reduced by 42*5% by pretreatment with 0.1 mM nicardipine but not by 10 mM verapamil, nifedipine, nimodipine or diltiazem, or by 50 mM La3+ or Ni2+. Pretreatment with 10 mM t-butyl hydroperoxide for 40 min did not affect 10 mM ATP-induced [Ca2+]i increase. Together, the results show that t-butyl hydroperoxide induced significant [Ca2+]i increase in PC12 cells by causing store Ca2+ release from the thapsigargin-sensitive endoplasmic reticulum pool in an inositol 1,4,5-trisphosphate-independent manner and by inducing Ca2+ influx via a nicardipine-sensitive pathway.