The effect of Ginkgo biloba in isolated ischemic/reperfused rat heart. A link between vitamin E preservation and prostaglandin biosynthesis

The effect of Ginkgo biloba extract (EGb 761) was studied in rat hearts submitted to ischemia/reperfusion. Isolated hearts perfused in Langendorff mode were subjected to 60 minutes of global ischemia and 15 minutes of reperfusion. EGb 761 was administered by chronic or acute treatment: intra-peritoneal injections of 5 mg/Kg extract for 5 days or 100 mg /L extract addition to the perfusion buffer, respectively. In hearts untreated with EGb 761 ischemia induced 20% decrease of membrane alpha-tocopherol concentration. This effect was not worsened by reperfusion. alpha-tocopherol consumption was accompanied by about 650% increase in 6-ketoPGF1alpha release within 3 minutes of reperfusion. Moreover, ischemia induced activation of transcription factor NF-kB. In both chronic and acute treatment with EGb 761 heart concentration of alpha-tocopherol was completely spared during ischemia as much as after reperfusion and a significant decrease of 6-ketoPGF1alpha release at 3 minutes of reperfusion was observed as compared with the untreated group. Nuclear translocation of NF-kB was lowered during ischemia. EGb 761 could act as direct free radical scavenger or as tocopheryl radical recycler; in both cases sparing membrane vitamin E should affect phospholipase A2 activity. Finally, EGb 761, by lowering ROS produced during ischemia, challenges nuclear translocation of NF-?B.