[Time-dependent Protein Expressions of MMP-2 and MMP-9 in Liver Contusion Rats after Impact]

Objectives: To observe the protein expression patterns of matrix metalloproteinase （MMP）-2 and MMP-9 in the liver tissue of liver contusion rats at different time after impact.

Methods: Fifty healthy adult male SD rats were randomly and evenly divided into control group and experimental groups （1 h, 3 h, 6 h, 12 h, 18 h, 24 h, 3 d, 5 d, 7 d after liver contusion）. A rat liver contusion model was established by a free-falling device. The rats were killed at corresponding time, and the contused hepatic lobes were extracted. The protein expressions of MMP-2 and MMP-9 in contused liver tissue of the rats in each group were observed by immunohistochemical staining （SP method） and Western blotting.

Results: After the liver contusion, the expression of positive cell and the protein semiquantitative result showed that the protein expression of MMP-2 enhanced at 6 h and peaked at 24 h, then decreased gradually at 3-5 d, and returned to normal levels at 7 d. The difference of expression between group and its previous adjacent group after 6 h （except 18 h） had statistical significance （P<0.05）. The protein expression of MMP-9 rose obviously at 1 h after liver contusion and peaked at 18 h, then decreased gradually at 3-7 d which still higher than control group. The expression difference between group and its previous adjacent group （except 12 h and 24 h） had statistical significance （P<0.05）.

Conclusions: The protein expressions of MMP-2 and MMP-9 in contused liver tissue after impact show good time-dependent patterns, which may provide important reference indicators for the time estimation of liver contusion.