Effects of hypoxia on caspase-3 activity in fetal superior colliculus : in vivo optical imagings

我们研究了缺氧对胚胎大鼠（胚胎第22天）上丘（SC） caspase-3活性的影响，该胚胎仍通过脐带与麻醉后的小脑相连。胎儿用氨基甲酸乙酯麻醉，三硫代胆碱麻痹。采用荧光Caspase-3底物测定Caspase-3活性。阻断脐带诱导缺氧5 ~ 10min。闭塞引起caspase-3活性短暂升高。在阻断后2或3小时，与初始阻断相比，阻断诱导的caspase-3激活变得更加强大和持久。脐带再灌注后，caspase-3活性立即升高，随后恢复到对照水平。显示caspase-3活性恢复的胎儿可以从缺氧中存活下来。caspase-3抑制剂和环孢素a可明显抑制caspase-3对缺氧的反应。已知环孢素a可以抑制线粒体中细胞色素c的释放，从而通过半胱天冬酶诱导细胞凋亡。超氧化物歧化酶（SOD）对caspase-3活性无影响。这些结果表明，胎儿SC神经元中的caspase-3活性在缺氧后发生可逆变化，这可能与缺氧损伤的保护有关。

We studied effects of hypoxia on caspase-3 activity in the superior colliculus (SC) in a fetal rat(embryonic day 22), which was still connected with the anesthetized dam by the umbilical cord. The fetuse was anestethized by urethane and paralyzed by gallamine triethiodide. Caspase-3 activity was measured by using fluorescent caspase-3 substrate. Hypoxia was induced by occlusion of the umbilical cord for 5-10 min. The occlusion caused a transient rise in caspase-3 activity. At 2 or 3 hrs after the occlusion, caspase-3 activation induced by occlusion became more robust and long-lasting compared to the initial occlusion. After reperfusion of the umbilical cord bessels, caspase-3 activity immediately increased and afterward recovered to the control level. Fetuses showing the recovery of caspase-3 activity were found to be survival from hypoxia. The responses of caspase-3 to hypoxia were markedly suppressed by a caspase-3 inhibitor and cyclosporin-A. Cyclosporin-A is known to inhibit a release of cytochrome-C from mitochondria, which induces apoptosis via caspases. Also, superoxide dismutase (SOD) was no effect on caspase-3 activity. These results suggest that caspase-3 activity in fetal SC neurons changes reversibly following hypoxia, which may be associated with protection from hypoxic insults.