Objective To investigate the effect of N-methyl-N-nitrosourea (MNU) on expressions of interphotoreceptor retinoid-binding protein (IRBP) and recoverin in rat retinal.Methods Thirty female Sprague-Dawley (SD) rats were randomly divided into five groups,including normal control group,and MNU treatment one day,three days,seven days and 10 days groups,each group had six rats.Rats in MNU-treatment groups received a single intraperitoneal injection of 40 mg /kg MNU,while rats in the normal control group received intraperitoneal injection of saline 5 ml/kg.Reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence were used to detect the retinal expression of IRBP and recoverin.Results RT-PCR results indicated that retinal IRBP levels decreased after MNU injection compared with normal control (P＜0.01),while recoverin levels increased (one day:P＞0.05; three days:P＜0.05; seven days:P＜0.5; 10 days:P＜0.05).Immunofluorescence assays demonstrated that normally IRBP protein is mainly in the inner and outer segments of photoreceptors.After MNU treatment,IRBP protein was detected in all retinal layers but much faint.Recoverin was expressed in the inner nuclear layer,inner plexiform layer and ganglion cell layer,and its expression was increased after MNU injection.Conclusion MNU suppresses IRBP expression and promotes recoverin expression in rat retina.%观察N-甲基-N亚硝脲(MNU)诱导的大鼠视网膜损伤对光感受器间维生素A类结合蛋白(IRBP)和恢复蛋白(recoverin)在视网膜中的表达变化.方法雌性Sprague-Dawley大鼠30只随机分为正常对照组和MNU处理1、3、7、10d组,每组均为6只大鼠.不同时间MNU处理组大鼠按体重40 mg/kg给予一次性腹腔注射MNU;正常对照组大鼠腹腔注射生理盐水5 ml/kg.逆转录-聚合酶链反应(RT-PCR)和免疫荧光检测各组大鼠视网膜中IRBP和恢复蛋白的mRNA及蛋白表达.结果 RT-PCR检测结果显示,与正常对照组比较,不同时间MNU处理组IRBP的mRNA表达水平随MNU作用时间增加而逐渐降低,差异均有统计学意义(P＜0.01)；恢复蛋白的mRNA表达水平随MNU作用时间增加而逐渐升高.MNU处理1d组恢复蛋白的mRNA表达水平与正常对照组比较,差异无统计学意义(P＞0.05)；MNU处理组3、7、10d组恢复蛋白的mRNA表达水平与正常对照组比较,差异均有统计学意义(P＜0.05).免疫荧光显微镜观察结果显示,正常对照组大鼠视网膜IRBP主要表达在光感受器细胞内、外节；不同时间MNU处理组IRBP在视网膜各层均有表达并随MNU作用时间增加而逐渐降低.恢复蛋白阳性标记物主要见于视网膜内核层、内丛状层及节细胞层,随MNU作用时间增加恢复蛋白的表达逐渐增强.结论MNU可降低IRBP的表达,但增加恢复蛋白的表达.
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