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目的 通过给孕鼠孕期补充维生素B12,观察宫内发育迟缓(IUGR)仔鼠体格生长规律、脑结构变化及脑组织中髓鞘碱性蛋白(MBP)的动态表达,以探讨孕期补充维生素B12对IUGR仔鼠脑损伤的影响.方法 将受孕成功的SD大鼠随机分为正常对照组(CC组)和IUGR模型组(S组),再按孕期是否补充维生素B12,将S组随机分为维生素B12干预组(SV组)和非干预组(SC组).CC组母鼠自孕1 d开始给予21%正常蛋白饮食,而S组母鼠自孕1 d开始给予6%蛋白饮食,建立IUGR模型.同时SV组母鼠自孕1 d开始给予维生素B12 150 μg/d灌胃,直至分娩.仔鼠生后由正常喂养的母鼠哺乳喂养.测量仔鼠生后1、7、14和21 d体重、头臀长及脑湿重,分别采用HE染色观察海马结构的变化,免疫组化半定量测定海马组织中MBP的表达水平,Western blot检测海马组织中MBP含量的动态表达.结果 (1)与CC组相比,生后1、7、14 d S组仔鼠形体瘦小,体重、头臀长、脑湿重均降低(P＜0.05),经追赶生长,到21 d时,三组仔鼠体重、头臀长差异无统计学意义(P＞0.05),但脑湿重差异仍具有统计学意义(P＜0.05).(2)与CC组相比,生后1、7、14和21 d S组仔鼠海马神经元细胞排列疏松、紊乱,部分细胞水肿明显,出现空泡,核固缩细胞较多,神经元细胞数目减少.与SC组比较,SV组仔鼠海马神经元细胞数目、出现空泡的细胞数目均较少,细胞排列形态相对致密、规则.(3)三组海马组织中MBP在生后1、7 d时均无明显表达,从14 d时表达逐渐增加,21 d时最强;Western blot检测也显示同样的表达趋势.在14 d和21 d三组中MBP的表达,SC组表达最低,其次为SV组,CC组的表达最高.结论 孕期补充维生素B12可能对IUGR脑损伤具有改善作用.“,”Objective To observe the changes in brain structure, physical growth in intrauterine growth retardation (IUGR) rats and the expression of myelin basic protein (MBP) in brain after prenatal vitamin B12 supplement. To discuss the influence of prenatal vitamin B12 supplement on the brain development of IUGR rats. Methods The pregnant Sprague-Dawley rats were divided into normal control group (group CC) and IUGR group (group S) randomly, then the rats in group S were distributed into two groups such as group SV and group SC, based on the supplements of prenatal vitamin B12 or not. The rats in group CC were given 21% of normal protein diet since the rats got pregnant; while the rats in group S will be given 6% protein diet to build IUGR model in the same condition. At the same time, the rats in group SV, which is given 6% protein diet will be supplied with vitamin B12 150 μg/d by gastric perfusion until delivery. The offspring rats were fed by maternal breastfeeding by the pregnant rats, who were given 21% normal protein diet and running water. We chose 1, 7, 14 and 21 d as for 4 different time points. In every time point, we observe the offspring body weight, crown-rump length, brain weight and take brain for study. For the brain samples, hippocampus structure was observed with HE stain method, while dynamics expression of MBP in hippocampus was observed with immunohistochemistry method and Western blot method. Results 1.At 1, 7, 14 d compared with rats in group CC, the rats in group S were thinner and shorter, and their body weight, crown-rump and brain weight was lower (P＜0.05). After catch-up growth, at 21 d, there were no obvious differences between group CC and group S (P＞0.05), except brain wet weight (P＜0.05). 2.At 1, 7, 14, 21 d compared with group CC, the neuronal cells located in the hippocampus from the rats in group S were held the states such as loosely arranged, edema, vacuoles, nuclear condensation, and soon on. And the numbers of the neuronal cells decreased. The conditions of the neuronal cells in group SV were better than those in group SC. 3.According to the experimental results, it was shown that the expression of MBP in hippocampus were not detected until the rats was 14 days old. With time going by, the expression of MBP were higher. Besides, the expression of MBP were distinct among the three groups at the same time point. The group CC held the highest expression, followed by group SV, and the lowest one was group SC. Conclusion Vitamin B12 supplementation during pregnancy may be ameliorating the brain damage caused by the IUGR condition.