AIM: To study the role of hepatic sinusoidal capillarization and perisinusoidal fibrosis in rats with alcohol-induced portal hypertension and to discuss the pathological mechanisms of alcohol-induced hepatic portal hypertension.METHODS: Fifty SD rats were divided into control group (n=20) and model group (n=30). Alcoholic liver fibrosis rat model was induced by intragastric infusion of a mixture containing alcohol, c oil and pyrazole (1 000:250:3). Fifteen rats in each group were killed at wk 16. The diameter and pressure of portal vein were measured. Plasma hyaluronic acid (HA), type Ⅳ collagen (CoⅣ) and laminin (LN) were determined by radioimmunoassay. Liver tissue was fixed in formalin (10%) and 6-μm thick sectiors were routinely stained with Mallory and Sirius Red. Liver tissue was treated with rabbit polyclonal antibody against LN and ColⅣ. Hepatic non-parenchymal cells were isolated,total protein was extracted and separated by SDS-PAGE.MMP-2 and TIMP-1 protein expression was estimated by West blotting.RESULTS: The diameter (2.207 ± 0.096 vs 1.528 ± 0.054 mm, P＜0.01) and pressure (11.014±0.395 vs 8.533±0.274 mmHg, P＜0.01) of portal vein were significantly higher in model group than those in the control group. Plasma HA (129.97±16.10 vs 73.09±2.38 ng/mL, P＜0.01), ColⅣ (210.49±4.36 vs 89.65±4.42 ng/mL, P＜0.01) and LN (105.00±7.29 vs 55.70±4.32 ng/mL, P＜0.01) were upregulated in model group. Abundant collagen deposited around the central vein of lobules, hepatic sinusoids and hepatocytes in model group. ColⅠ and ColⅢ increased remarkably and perisinusoids were almost surrounded by ColⅢ.Immunohistochemical staining showed that ColⅣ protein level (0.130±0.007 vs 0.032±0.004, P＜0.01) and LN protein level (0.152±0.005 vs 0.029±0.005, P＜0.01)were up-regulated remarkably in model group. MMP-2 protein expression (2.306±1.089 vs 0.612±0.081,P＜0.01) and TIMP-1 protein expression (3.015±1.364 vs 0.446±0.009, P＜0.01) in freshly isolated hepatic nonparenchymal cells were up-regulated in model group and TIMP-1 protein expression was evidently higher than MMP-2 protein expression (2.669±0.170 vs 1.695±0.008,P＜0.05).CONCLUSION: Hepatic sinusoidal capillarization and peri-sinusoidal fibrosis are responsible for alcoholinduced portal hypertension in rats.