AIM: To investigate the effect of ginkgo biloba (EGb) extract on metabolism of oxygenic free radicals after subarachnoid hemorrhage (SAH) and to observe the influence whether or not shows a dose-depended manner.METHODS: ① The experiment was completed in the Microcirculatory Laboratory of Taishan Medical College and the Central Laboratory of Affiliated Hospital of Taishan Medical College from May to December 2003. Fifty-four Wistar rats were used in the experiment and were divided into control group (n=6), model group (n=12), vehicle group (n=12), 100 mg/kg EGb extract group (n=12) and 200 mg/kg EGb extract group (n=12). ② The femoral artery was cannulated for blood withdrawing. The autologus arterial hemolysate was obtained by a freeze-melt method and then it was injected into the rat's cisterna magna to produce SAH models (SAH models were established in all groups except control group). ③ Control group: The hemolysate was replaced by 0.3 mL saline. Model group: No intervention was given after SAH. Vehicle group: The same volume of saline containing tween 80 was injected intraperitoneally. 100 mg/kg EGb extract group and 200 mg/kg EGb extract group: The rats received intraperitoneal injection of EGb (100 mg/kg and 200 mg/kg respectively) 30 minutes before cisternal injection, and the injection was repeated twice daily with the half dose. EGb was brown-yellow power and provided by Lvyuan Pharmaceutical Co. Ltd, standardized on the amount of ginkgo bitter lactone ≥ 6%, flavone glycosides ≥ 24%. EGb was solubilized in a drop of tween 80 and physiological saline (3% and 6% respectively). The stock solution of EGb was prepared just before use. Above interventions were not ceased until 12 hours after sampling.
④ 24 hours and 72 hours after cisternal injection, rats were sacrificed for determination of superoxide dismutase (SOD) activity and content of malondialdehyde (MDA) in the brain tissue homogenate. The manipulation followed by the instruction books of SOD and MDA kits provided by Nanjing Jiancheng Bioengineering Institute. ⑤Measurement data were compared with analysis of variance. RESULTS: Totally 54 rats entered the statistical analysis. ① SOD activities in brain tissue: Activities in model group and vehicle group were lower than those in control group 24 hours and 72 hours after modeling (P < 0.01), but those in 100 mg/kg and 200 mg/kg EGb extract groups were higher than those in model group (P < 0.01). The difference was not significant between 100 mg/kg EGb extract group and 200 mg/kg EGb extract group. ② MDA content: Contents in model group and vehicle group were higher than those in control group 24 hours and 72 hours after modeling (P < 0.01), but those in 100 mg/kg and 200 mg/kg EGb extract groups were lower than those in model group (P < 0.05-0.01). The difference was not significant between 100 mg/kg EGb extract group and 200 mg/kg EGb extract group.CONCLUSION: EGb may alleviate cerebral injury caused by oxygenic free radicals without obvious dose-depended effect after SAH.