预吸氧对大鼠脑皮质神经元损伤的影响

The Effects of Preoxygenation on Neuronal Injury of Cerebral Cortex in Rats

目的：观察不同浓度预吸氧、缺氧和复氧对大鼠脑皮质神经元损伤的影响。方法：72只成年雄性Wistar大鼠随机分为A、B、C 3组,每组又分为4个亚组。AⅠ-AⅣ（预吸氧）亚组分别吸入21%、50%、75%和95%氧30min;BⅠ-BⅣ（预吸氧-缺氧）亚组按A组方法处理后再吸入5%氧20min;CⅠ-CⅣ（预吸氧-缺氧-复氧）亚组按B组方法处理后,再吸入98%氧20min。取各组大鼠大脑皮质,测定乳酸（LA）、丙二醛（MDA）、氧自由基（OFR）、总抗氧化能力（T-AOC）、总超氧化物歧化酶（T-SOD）、过氧化氢酶（CAT）、谷胱甘肽过氧化物酶（GSH-Px）和氨基酸的含量或活力。用免疫组化法检测诱导型一氧化氮合酶（iNOS）。在光镜下观察神经元形态学改变。结果：AⅠ、AⅡ亚组神经元无明显改变,AⅢ、AⅣ亚组神经元轻度肿胀。B组神经元肿胀明显,以BⅢ、BⅣ亚组较为严重。C组神经元胞核固缩,核仁缩小、消失,其中以CⅡ亚组最轻,CⅢ、CⅣ亚组最重,甚至可见核裂解、消失、只残余细胞轮廓的鬼影细胞。与AⅠ亚组相比,AⅢ-AⅣ亚组OFR、iNOS和LA增加（P〈0.05）,提示这三种损伤因子参与了脑损伤;T-AOC增加（P〈0.05）,可能是由于损伤因子引起了某些抗氧化因子的反馈性增加;T-SOD降低（P〈0.05）,可能与其消耗增加有关。CⅠ-CⅢ亚组的OFR和CⅠ、CⅣ亚组的iNOS以及CⅡ、CⅣ亚组的LA高于A组中各对应亚组（P〈0.05）,提示复氧性脑损伤可能与这三种因子的增加有关。结论：75%以上浓度预吸氧可引起大鼠轻微脑损伤,并使随后发生的缺氧复氧性脑损伤加重。50%浓度预吸氧不引起大鼠脑损伤,并可使随后发生的缺氧复氧性脑损伤减轻。

Objective： To observe the effects of preoxygenation, anoxia and reoxygenation on neuronal injury of cerebral cortex in rats. Methods： Seventy-two Wistar rats were randomly allocated to one of three equal groups： preoxygenation （A）, hypoxia （B） and reoxygenation （C）, and those in each of the groups ware randomly divided into four equal subgroups according to the different preoxygenation concentration . The rats in group A Ⅰ -AⅣ were individually exposed to preoxygenation with different concentration of oxygen （21%, 50%, 75% and 95% ） for 30 min, in group BⅠ -BⅣ were exposed to hypoxia air with 5% oxygen for 20 rains after preoxygenation as group A and in group C Ⅰ -C Ⅳ were exposed to 98 % oxygen for 20 min for the reoxygenation after preoxygenation and hypoxia as group B. The brain samples were removed for the histologic examination and the determination of oxygen free radicals （OFR）, exiting amino acid （EAA）, inhibiting amino acid （IAA）, malondialdehyde （MDA） and lactate （LA） content, total superoxide dismutase （T-SOD）, glutathione peroxidase （GSHpx） and catalase （CAT） activities, total antioxidation capacity （T-AOC） as well as the number of induce nitric oxide synthase （iNOS） positive cells. Results： Slightly edema was observed in neurons of AⅢ and AⅣ. The injury in group B was more serious than that in group A and less than that in group C. The injure degree was slightest in subgroup Ⅱ and the most serious in subgroup Ⅲ and Ⅳ among the four subgroups of group C and group B. The values of OFR, iNOS, LA and T-AOC ware increased and the activities of T-SOD decreased significantly in subgroup AⅢ and AⅣ as compared with those in subgroup AⅠ. The OFR in subgroup CⅠ -CⅢ, the INOS in subgroup CⅠ and C Ⅳ, and thd LA in subgroup CⅡ and CⅣ increased as compared with those in the homologous subgroups in group A. Conclusion： Preoxygenation with 50% concentration may reduce the brain injury caused by anoxia and reoxygenation without any disadvantageous effect on the histology of neurons and high concentration preoxygenation with above 75 % concentration may cause the brain injury marked by edema in the neurons and the injury reduced by anoxia and reoxygenation in rots.