Abstract: Objective To observe effects of ethanol on phagocytosis,actin expression,and membrane fluidity in Kupffer cells (KCs) in vitro.Methods KCs were isolated from rats with collagenase perfusion and density ladder centrifugation technique.The isolated KCs were cultured with ethanol (1,2,and 4 g/L) for 3 or 24 hours;then,phagocytosis,actin expression,and membrane fluidity of the KCs were determined with beads phagocytosis test,fluorescence staining,and fluorescence polarization.Results The number of phagocytosed beads for the KCs treated with ethanol at 1,2,and 4 g/L were 16.05±3.69,15.86±4.50,and 13.86±4.69 at 3-hour and 13.95±4.51,14.35±6.52,and 9.71±3.34 at 24-hour,which were significantly lower than those of the control group (20.13±5.26 and 20.3±8.57;P<0.05 for all);the phagocytic function of the KCs treated with 4 g/L ethanol for 24 hours was significantly lower than that of KCs treated with 1 and 2 g/L ethanol (both P<0.05).The microfilaments of KCs in all ethanol treatment groups were arranged in a disorderly manner,but there was no significant difference in actin expression among the groups (P>0.05).Compared with that of the control group (5.85±1.13),the membrane fluidity of KCs in 2 and 4 g/L ethanol treatment groups (2.30±1.08 and 1.62±0.30)was decreased in a dose-dependant manner significantly (both P<0.05).Conclusion Ethanol could decrease the phagocytosis of KCs in vitro,and the effect may be related to the changes in membrane fluidity and the expression of microfilaments of in KCs.