N-甲基-N-亚硝脲对猫视网膜光感受器细胞损害的研究

摘要

背景 合理的视网膜色素变性(RP)动物模型的建立方法是进行RP干预和治疗的重要工具和手段.研究证实,N-甲基-N-亚硝脲(MNU)可造成哺乳动物光感受器细胞的选择性损害,但是否MNU可用于建立RP动物模型的报道较少.目的 评估MNU对猫视网膜光感受器细胞的毒性损害作用.方法 20只2岁龄的猫一次性股静脉注射MNU,并按照注射剂量的不同分为20、25、30、35、40mg/kg MNU组,每组4只.另外4只猫股静脉注射等量生理盐水作为对照组.MNU注射后每日观察实验猫的行为变化、瞳孔大小及对光反射情况,分别于注射后24h、72h、7d和14d用静脉注射过量的质量分数2%戊巴比妥钠处死实验猫,眼球摘除后制备视网膜切片进行组织病理学检查,评估不同剂量MNU对视网膜光感受器的影响.结果 不同剂量MNU组的实验猫注射MNU 7d后瞳孔散大,对光反射迟钝.MNU注射24h,猫视网膜光感受器细胞的损害以核固缩和排列紊乱为主,MNU注射72h,视网膜光感受器细胞的损害以外核层变薄和细胞碎裂为主,MNU注射7d后,40mg/kg注射组的实验猫均死亡,光感受器细胞层仅存在极少量细胞,MNU注射14d,视网膜光感受器细胞层均完全消失.各组视网膜损害程度与注射MNU剂量有关.结论 MNU可以造成猫视网膜光感受器细胞的严重损害,MNU对视网膜光感受器的作用呈时间和剂量依赖性.%Background To establish the ideal animal model of retinitis pigmentosa (RP) is very important for onward relevant study.Previous research determined that N-methyl-N-nitrosourea (MNU) can selectively damage photoreceptors via intravenous injection in mammal.However,whether MNU can be used to create an RP model needs to be investigated.Objective This experiment was designed to evaluate the toxic effect of MNU on photoreceptor cells of cats.Methods MNU was injected into 20 2-year-old cats via femoral vein and randomized into 20mg/kg, 25mg/kg, 30mg/kg, 35mg/kg and 40mg/kg MNU groups,and equal amount of normal saline solution was used in the same way in 4 normal cats as the control group.The activity,pupil size and light reflex were observed after injection of MNU.The cats were sacrificed and eyeballs were enucleated for histological examination to evaluate the structural and morphological changes of photoreceptors at 24 hours,72 hours,7 days and 14 days after the administration of MNU.This experimental study complied with the Statement for the Use of Animals in Ophthalmic and Vision Research.Results Dilated pupil and inertia of light reaction were found in experimental cats on the 7th days in the various groups.In 24 hours after MNU injection,the damage of photoreceptors was primarily characterized by pyknosis and disorder.In 72 hours after MNU injection,attenuation of the outer nuclear layer and disruption of cells were seen.Loss of photoreceptors and disappearance of the outer nuclear layer were observed on the 7th and 14th day.The extent of retinal photoreceptor cell damage was dependent on the dose of MNU.Conclusion MNU can selectively induce serious damage of the photoreceptor cells in cats retina in a time- and dose-dependent manner.