region-specific oxidant stress in the anoxic-reoxygenated embryonic

The ability of the developing myocardium to tolerate oxidative stress during early gestation is an important issue with regard to possible detrimental consequences for the fetus. In the embryonic heart, anti-oxidant defences are low, whereas glycolytic flux is high. The pro-and antioxidant mechanisms and their dependency on glucose metab-olism remain to be explored. Isolated hearts of 4-day-old chick embryos were exposed to normoxia (30 min), anoxia (30 min), and hyperoxic reoxygenation (60 min). The time course of ROS produc-tion in the whole heart and in the atria, ventricle, and outflow tract was established using lucigenin-enhanced chemiluminescence. Cardiac rhythm, conduction, and arrhythmias were determined. The activity of superoxide dismutase, catalase, gutathione reductase, and glutathione peroxidase as well as the content of reduced and oxidized glutathione were measured. The relative contribution of the ROS-generating systems was assessed by inhibition of mitochondrial complexes I an