不同辐射剂量对西藏小型猪小肠线粒体的影响

摘要

Objective To investigate the injuries of intestinal mitochondria induced by different doses of whole-body radiation in Tibet minipigs. Methods Eighteen Tibet minipigs were randomized into 5 radiation groups (n=3) and a control group (n=3). The minipigs in the radiation groups were subject to a total body X-ray radiation at 2, 5, 8, 11, or 14 Gy, and 72 h after the exposure, the mRNA expressions of the intestinal mitochondrial genes were examined using RT-PCR. The changes in the respiratory chain complexes I-IV and the respiratory functions of succinate and NADH were assayed, and the intestinal ultrastructures were observed using transmission electron microscopy (TEM) following the exposures. Results Compared with those in the control group, the expression levels of the related mitochondrial genes, the activities of the respiratory chain complexes and the function of the respiratory chain were significantly lowered in the radiation groups. At the doses below 8 Gy, the exposures caused significant reduction in the measurements as the radiation doses increased, but at higher doses, these measurements showed no further reductions, Ultrastructurally, exposures at 2 and 5 Gy caused mitochondrial expansion and mild reduction of the density, whereas radiation at 8 Gy or greater resulted in vacuolar changes and obvious expansion of the mitochondria with damages of the mitochondrial cristae and membranes. Conclusion Below the doses of 8 Gy, intestinal mitochondrial damages in the minipigs increase with the radiation dose, but at higher doses, the damages do not further increase with the radiation dose.%目的 观察不同剂量X线全身照射对西藏小型猪小肠线粒体的影响及其变化特点.方法 将18头成年,健康,雄性西藏小型猪分为6组.实验组5组,对照组1组(n＝3头/组).分别接受2,5,8,11,14 Gy全身X线照射.照射后72 h麻醉处死并采集小肠组织分别检测线粒体相关基因的表达,线粒体呼吸链复合酶Ⅰ,Ⅱ,Ⅲ和Ⅳ活性,线粒体琥珀酸氧化呼吸链和NADH氧化呼吸链的功能及观察线粒体的超微结构.结果 8 Gy以下剂量组的线粒体蛋白编码相关基因表达、呼吸链复合物活性及呼吸功能明显低于对照组且随放射剂量的增加而降低；而8 Gy以上剂量组,上述指标虽仍明显低于对照组,但不再随放射剂量的增加而继续降低并维持于一较低水平.电镜下线粒体超微结构在2,5 Gy时的改变主要表现为线粒体的扩张及轻微的电子密度降低.8 Gy及其后的剂量组则观察到更为明显的电子密度降低及线粒体的空泡化,嵴与线粒体外膜的连接缺失等.结论 电离辐射导致的小肠线粒体损害在一定剂量范围内(8 Gy以下)随放射剂量的增加而愈发明显；但接受更高强度的照射后,其损伤程度并不会随放射剂量的增加而继续增加.