空间飞行与过氧化损伤

空间飞行与返回1G环境后的过氧化损伤密切相关,长期空间飞行损伤更为明显,着陆后这种效应甚至可持续几周。在人体表现为红细胞膜的脂质过氧化程度增加、某些血液中的抗氧化物含量减少,8-iso-prostaglandin和8-oxo-7,8-dihydro-2-deoxyguanosine的尿排出增加。8-iso-prostaglandin和8-oxo-7,8-dihydro-2-deoxyguanosine分别为脂质和DNA氧化损伤的标记物。上述改变应归结为飞行过程中出现的营养缺乏和恢复期急待补充营养的肌肉与其他组织对氨基酸的竞争等复合作用。对啮齿动物的研究极大地补充了人体观察结果。大多数啮齿动物实验表明飞行后脂质过氧化产物增加,而抗氧化酶活性下降,是由于返回地球重力时的应激反应。在食品中添加抗氧化物可减轻内源性氧化防御和氧化物合成之间的失衡,改善飞行后氧化应激状态。

Space Flight and Peroxidative Damage

Space flight is associated with an increase of peroxidative damage after returning to 1 g. The effect is more pronounced after long-duration space flight and can even last for several weeks after landing. In humans there is increased lipid peroxidation in erythrocyte membranes, reduced blood antioxidants, and increased urinary excretion of 8-iso-prostaglandin F2alpha, and 8-oxo-7, 8 dihydro-2 deoxyguanosine. Isoprostane 8-iso-prostaglandin F2alpha and 8-oxo-7, 8 dihydro-2 deoxyguanosine are markers for oxidative damage to lipids and DNA, respectively. The changes are attributed to a combination of energy deficiency that occurs during flight and substrate competition for amino acids occurring between repleted muscle and other tissues during the recovery phase. The observations in humans have been complemented by studies in rodents, which showed increased production of lipid peroxidation products and decreased antioxidant enzyme activity afterflight. The changes in rodents were attributed to the stress associated with re-entry into Earth's gravity. Reducing the imbalance between the production of endogenous oxidant defenses and oxidant production by increasing the supply antioxidants in diet may lessen the severity of the postflight increase in oxidative stress.