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

本实验研究了缺氧对胚胎22天的大鼠上级丘（SC）中半胱氨酸天冬氨酸蛋白酶（caspase）-3活性的影响。胎儿用乌拉坦麻醉，并用三乙基碘化镓胺麻痹。Caspase-3荧光底物法测定Caspase-3活性。缺氧引起的闭塞的脐带5-10分钟。闭塞引起caspase-3活性的短暂上升。在闭塞后2或3小时，闭塞诱导的半胱天冬酶-3活化变得更加强大和持久相比，初始闭塞。再灌注后，caspase-3活性立即升高，随后恢复到对照水平。发现显示半胱天冬酶-3活性恢复的胎儿从缺氧中存活。Caspase-3抑制剂和环孢素A可明显抑制Caspase-3对缺氧的反应。已知环孢菌素-A抑制细胞色素-C从线粒体的释放，其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活性在缺氧后可逆地变化，这可能与保护缺氧损伤有关。

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.