Objective To investigate the effects of urotensin Ⅱ/urotensin Ⅱreceptor ( UⅡ/UT) system on the expression of inflammatory signal molecules p 38 mitogen-activated protein kinase ( p38 MAPK) and nuclear factor-κB ( NF-κB ) in lipopolysaccharide ( LPS )-stimulated Kupffer cells ( KCs ) . Methods Rat KCs were isolated and purified by means of in situ perfusion and density gradient centrifuga-tion.The isolated cells were randomly divided into six treatment groups including group 1:UⅡ(-) urantide (-)LPS(-), group 2:UⅡ(+)urantide(-)LPS(-), group 3: UⅡ(-)urantide(+)LPS(-), group 4:UⅡ(-)urantide(-)LPS(+), group 5:UⅡ(+) urantide(-) LPS(+) and group 6:UⅡ(-)urantide(+) LPS(+) .Western blot assay was performed to detect p 38 MAPK/p-p38 MAPK protein and NF-κB p65 sub-unit.The DNA-binding activity of NF-κB was tested by electrophoretic mobility shift assay (EMSA).Re-sults There was no significant difference with the expression of p 38 MAPK protein in KCs among the six groups (P>0.05).The expression of p65 protein and p-p38 MAPK and the DNA-binding activity of NF-κB were significantly enhanced in LPS-stimulated KCs from groups 4, 5 and 6 in comparison with those in group 1 (P<0.01).No significant differences with the levels of p65 protein and phosphor-p38 MAPK and the DNA-binding activity of NF-κB were observed between UⅡ/urantide-treated cells ( group 2 or group 3) and untreated cells (group 1) (all P>0.05), but that were decreased in group 6 than those in group 4 (all P<0.01).Conclusion UⅡ/UT system participated in the activation of p38 MAPK and NF-κB signaling pathways in LPS-stimulated primary Kupffer cells .