Objective To observe the effect of acupuncture intervention at different time-points on the activity of superoxide dismutase(SOD)

glutathione peroxidase(GSH-PX)

the content of malonaldehyde(MDA)and expression of heat shock protein 70(HSP 70)of liver tissue in rats with simulated weightlessness

so as to explore its mechanism underlying improvement of liver injury in rats with simulated weightlessness.Methods Twenty male Wistar rats were randomly divided into control group

model group

pre-acupuncture group and EA group

5rats in each.The model of simulated weightlessness was established by tail suspension for 4week.One week before the tail suspension

the rats in the pre-acupuncture group were treated with electroacupuncture(EA)at"Shenshu"(BL 23)

"Pishu"(BL 20)and "Sanyinjiao"(SP 6)for 30 min before treatment

once a day for 7days.The rats in the EA group received tail suspension and acupuncture intervention at the same time.EA was applied for 30 min per treatment

once every other day for 14 times.Immunohistochemical staining was used to assay the expression of HSP 70 in the liver tissue.The activities of SOD and GSH-PX and content of MDA in liver tissues were examined by means of colourimetric method.Results Compared with the control group

the expression of HSP 70 and the content of MDA in the liver tissue were increased significantly(P<0.01)

and the activity of SOD and GSH-PX was notably reduced(P<0.05)in the model group.Compared with the model group

the content of HSP 70 was significantly reduced in the pre-acupuncture group(P<0.01).There were no significant changes in the levels of SOD

GSH-PX

MDA and HSP 70 in the EA group(P>0.05).In comparison with the pre-acupuncture group

the activity of GSH-PX was lower(P<0.05)and the content of MDA was higher(P<0.05)in the EA group.Conclusion EA-pretreatment can suppress the increase of liver HSP 70 immunoactivity in rats with simulated weightlessness

being likely to improve the antioxidant ability of liver.