Ginkgo biloba extract (EGb 761) modulates bleomycin-induced acute lung injury in rats

The effect of Ginkgo biloba extract (EGb 761) on bleomycin (BLM)-induced acute lung injury was studied in rats. The responsiveness of isolated pulmonary arterial rings to 5-hydroxytryptamine (5-HT) as well as the levels of some relevant biochemical markers in the lung tissue were taken as evidence for the acute lung injury. BLM was given intraperitoneally at a dose of 15 mg/kg/day for five consecutive days. It was found that BLM treatment attenuated the vasoconstrictor effect of 5-HT on the isolated pulmonary arteries. In lung tissues BLM also elevated the level of lipid peroxides and enhanced the activity of glutathione peroxidase. On the other hand, the level of glutathione and the activity of alkaline phosphatase were reduced. Body weight, lung weight and tissue glutathione-S-transferase activity were, however, not altered. Oral administration of EGb 761 at a dose of 100 mg/kg/day for five consecutive days did not alter any of the chosen biochemical parameters in the lung tissue except for a slight reduction in alkaline phosphatase activity. However, treatment with EGb 761 reduced the responsiveness of the pulmonary artery to 5-HT. Administration of EGb 761 (100 mg/kg/day; po) two hours prior to BLM (15 mg/kg/day; ip), for five consecutive days blunted the occurrence of further reduction in the vasoconstrictor response of the pulmonary artery to 5-HT. Furthermore, EGb 761 tended to normalize BLM-induced alterations in the measured biochemical markers in the lung tissue. The apparent modulatory influence of EGb 761 on BLM-induced acute lung injury stems, at least in part, from its beneficial free radical scavenging properties that provide the extract with antioxidant activity.