BK通道对大鼠脑缺血再灌注损伤神经细胞内钙离子浓度及凋亡的影响

Regulation of BK channel on intraceHular Ca2＋ level and neuronal cells apoptosis after focal cere- bral ischemia-reperfusion in rats

目的观察BK通道对脑缺血再灌注损伤神经细胞内钙离子浓度（[Ca2＋]，）和对神经元凋亡的影响。方法将108只SD大鼠随机分为假手术组（ss组，n=36）、脑缺血再灌注组（IR组，n=36）、脑缺血再灌注且脑室内Iberiotoxin（IBTX）处理组（IBTX组，n=36），分别比较各组在不同再灌注时间后神经功能缺损评分、脑梗死面积，利用激光共聚焦显微镜技术测定各组[Ca2＋]。浓度，免疫组织化学和TUNEL法分别检测BK通道表达和神经元细胞凋亡。结果IBTX处理组在再灌注24h后神经功能缺损评分为（2．17±0．44）明显高于IR组（1．83±0．42，P〈0．05）；脑梗死体积（27．97±5．84）％明显大于SS组（22．83±4．74）％（P〈0．05）；激光共聚焦显微镜结果显示：IBTX处理组24h点[Ca2＋]，为（914．50±86．57）nmol／L较SS组（732．09±51．30）nmol／L明显升高（P〈0．01），TUNEL细胞凋亡检测显示IBTX处理组24h神经细胞凋亡率为（15．20±6．11）％，与IR组（10．49±1．91）％比较差异有统计学意义（P〈0．05），免疫组织化学结果显示缺血再灌注损伤后BK通道的表达增加，但组间比较差异无统计学意义（P〉0．05）。结论在缺血状态下，BK通道对神经细胞具有保护作用，其机制很可能是通过降低神经细胞内钙离子浓度和减少细胞的凋亡。

Objective To investigate the regulation of BK channel on intracelullar free calcium concentration [ Ca2＋] i and apoptosis in neuronal cells in the rat brain following focalcerebral ischemia injury. Methods 108 SD rats were randomly assigned to sham group （n = 36）, ischemic reperfusion group （n =36）, IBTX group （n = 36 ）, compared neurological function defect and infarct size of different groups at the same reperfusing time. Laser scanning confocal microscope imaging of the calcium fluorescent indicator dye Fluo-2/AM was used to determine the changes of [ Ca2 ± ] in neurons, the expression of BK tunnel was investigated by immunohistochemistry and neuronal ceils apoptosis were measured by TUNEL. Results At 24 h after ischemic reperfusion, the neurological deficit scores in IBTX group were （2. 17 ± 0. 44 ）, which obviously higher than ischemic reperfusion group （ 1.83 ± 0. 42, P 〈 0.05 ） ;The brain infarct volume in IBTX group was （27. 97 ± 5.84） %, which larger than ischemic reperfusion group （22. 83 ± 4.74） % （ P 〈 0. 05 ）. The [ Ca2＋] i and the cell apoptosis rate of IBTX group had significant difference at 24 h after ischemic reperfusion compared with ischemic reperfusion group： （914. 50 ± 86. 57 ） nmol/L VS （732. 09 ± 51.30） nmol/L （P〈0.01）; （15.20 ±6. 11）% vs （10.49±1.91）% （P〈0. 05）.Theresultsofimmunohistochemistry indicate that the expression of BK channel in isehemic reperfusion group decreased, but the defference of three groups was not different significantly （P 〉 0.05 ）. Conclusion BK channels could play a role in protecting the neuronal cells in mice following cerebral ischemia-reperfusion by inhibited the ascension of [ Ca2＋]i and decrease neurons apotosis.