RESUMEN
<p><b>AIM</b>To observe the dynamic expression of ERK1 in fibrotic rat liver.</p><p><b>METHODS</b>The rat hepatic fibrosis was induced by bile duct ligation (BDL). Histopathological changes were evaluated by hematoxylin and eosin staining, and by Masson's trichrome method. ERK1 mRNA in liver was determined by reverse transcription-polymerase chain reaction (RT-PCR), while the distribution of ERK1 was assessed by immunohistochemistry. ERK1 protein was detected by using Western blotting analysis.</p><p><b>RESULTS</b>With the development of hepatic fibrosis, the positive cells of ERK1 increased a lot, they were mainly distributed at portal ducts, fiber septa and around the bile ducts, vascular endothelial cells and perisinusoidal cells. Western blotting analysis results displayed that the expression of ERK1 protein were up-regulated with model course, and its levels were the highest at week 4 after operation, achieving to 3.9-fold of that in normal rat liver. ERK1 mRNA expressed in normal rat livers as well, they were up-regulated at day 2 after BDL and its level was the highest at week 4 after BDL.</p><p><b>CONCLUSION</b>These data suggest that the expression of ERK1 and its mRNA can be increase greatly in fibrotic rat liver.</p>