Objective To investigate the change in expressions of lipoxin A4 (LXA4) and lipoxin A4 receptor (ALX) in rats with fat embolism syndrome(FES).Metbods Sixty healthy male SD rats were assigned to control group and FES group which was subgrouped at l,6,12 and 24 h according to the random number table,with 12 rats each.Allogeneic perinephric fat (0.706 ml/kg) was injected to rat caudal veins in FES group.Instead isotonic saline in an equal volume was given to rats in control group.Lung samples were harvested from each group to detect pathological morphology,concentration of total protein and LXA4 in bronchoalveolar lavage fluid (BALF),lung weight to dry ratio (W/D),and activity of myeloperoxidase (MPO) and ALX mRNA.Additional 40 SD rats were divided into control group,FES 24-hour group,BML-1 11 + FES 24-hour group,and Boc-2 + FES 24-hour group according to the random number table,with 10 rats each.Pathology of lung tissue was observed using microscopy and expression of lung MPO mRNA was detected.Results Lung tissues in FES group were seriously injured compared with control group.Total protein concentration in BALF was (71.12 ± 11.05) μg/ml in FES 12-hour group,significantly increased compared to (29.82 ± 0.64) μg/ml in control group (P ＜ 0.05).LXA4 concentration in BALF was (2.72 ± 0.24) ng/ml in FES 24-hour group,significantly higher than (0.69 ±0.05)ng/ml in control group (P ＜ 0.05).Lung W/D value was 9.13 ±0.83 and 9.60 ±0.86 respectively in FES 6-hour and 12-hour groups,higher than 3.09 ±0.10 in control group (P ＜0.05).Activity of MPO in lung tissue was (0.74± 0.07)U/g and (0.53 ±0.08)U/g respectively in FES 6-hour and 12-hour groups,significantly higher than (0.19 ± 0.03) U/g in control group (P ＜ 0.05).Expression of ALX mRNA was 3.99 ± 1.09 in FES 24-hour group,significantly higher than 1.00 ±0.21 in control group (P ＜0.05).Expression of MPO mRNA was lower in BML-111 + FES 24-hour group (0.69-0.08) and was higher in Boc-2 + FES 24-hour group (2.05-0.14),when compared to 1.52 ±-0.07 in FES 24-hour group (P＜0.05).Conclusion LXA4 mainly involves in the resolution of inflammation in FES rats,which may be achieved at least in part by binding to ALX.