Empirical Study Of Different Doses Of Losartan In Cirrhotic Portal Hypertensive Colopathy Rats

Objective:To observe the therapeutic action and study the mechanism of angiotonin AT1 receptor blorcker losartan in rats with portal hypertensive colopathy(PHC). Explore the pathogenesy of PHC and reveal the effects of losartan on colonic mucosal microcirculation and submucosal ultra structure changes in rats.Methods: Portal hypertension (PHT) with cirrhosis was induced by composite factors after 56 days in 76 majority male Wister rats, another 16 as normal control group. Eight weeks later, hepatic venous pressure gradient(HVPG) was measured in 8 of 76 cirrhosis rats and 6 of normal control group and hepatic tissue was observed with light microscope. It was confirmed that PHT was successfully formed. Rats were divided into five groups: normal control group (n=10), cirrhotic model group (n=12), high dose treatment group(n=11) , moderate dose treatment group (n=11), low dose treatment group(n=11).The different treatment group were gavaged with losartan 10mg/kg/d,5mg/kg/d,2.5mg/kg/d respectively for 21 days. The rats in normal control group and cirrhotic PHT model group were given tap water only .Three weeks later, HVPG and MAP were measured in all the rats, colonic tissue was fixed by 10% formaldehyde, after paraffin imbedding, the nitricoxide synthase was observed by immunohistochemical staining and then analyzed by image analysis system. Other colonic tissue was fixed by 2% glutaraldehyde for two hours, then was put in sodium dimethylarsenate balanced solution. After conventional handling, it was observed by transmission electron microscope. The metabolin of nitrogen monoxidum in blood serum was detected with nitrate reductase method. The tumor necrosis factor in blood serum was detected with radio-immunity.Result: 1.The result of HVPG: HVPG in cirrhotic PHT model group was significantly increased than normal control group. Compared to the cirrhotic PHT model group, HVPG were significantly decreased in all treatment groups(p<0.05).There were no significant difference among treatment groups(p>0.05). High dose of losartan made mean arterial pressure(MAP) decreased significantly than other groups. 2.The result of light microscope study: Vascular areas and micrangium areas of submucosa in cirrhotic PHT model group was significantly increased compared to normal controls(p<0.01). Vessel wall of veinlet broking mucosa epithelial cell necrosis and red blood cells speading outside of the vessel were observed in cirrhotic PHT model group. Compared to the cirrhotic PHT model group, vascular areas of submucosa were significantly decreased in all treatment groups(p<0.01) and micrangium areas of submucosa were significantly decreased in high and moderate dose of treatment groups(p<0.05). The colonic mucosal epithelia had less damage in all treatment groups. 3.The result of transmission electron microscope study: The fragmentation of microvilli in mucosa epithelial cells and glandular epithelium cells was observed in cirrhotic PHT model group. Engorgement of endocytoplasmic reticulum and ribosome departing from it were observed. Engorgement of chondriosome and crista fragmentation were also seen in different kinds of cells. Microfilament and endothelial phagocytolytic vesieles in vascular endothelial cells were more in cirrhotic PHT model group. The arrangement of microvilli in mucosa epithelial cells and glandular epithelium cells were more concinnous in treatment group than model group. The damage of cell organelles were less in treatment group than those in model group. More secretory granule were found in the treatment group. Microfilament and endothelial phagocytolytic vesieles in vascular endothelial cells became less than those in model group. 4.The result of immunohistochemistry study: Compared to nomal control group the expression of iNOS in submucosal vascular endothelial cells in model group was significantly stronger(p<0.01). The expression of iNOS in treatment groups became thinner than model group. The difference between high dose treatment group and model group was significan(tp<0.05). But the expression of iNOS were no significant among the treatment groups(p>0.05). The expression of eNOS was mainly in submucosal vascular endothelial cells and there were no significant differences among model group and all treatment groups(p>0.05). The expression of eNOS in model and treatment groups were significantly stonger than that in normal control group(p<0.05). 5.The level of TNF-α: The level of TNF-αwas significantly higher in model group than nomal control group. Compared to model group the level of TNF-αwere significantly lower in high and moderate treatment groups(p <0.05). The difference between model group and low dose group was not significant(p>0.05).6.The level of nitrogen monoxidum: The level of nitrogen monoxidum in model group was significantly higher than nomal control group(p<0.01). Compared to model group , the level of nitrogen monoxidum in moderate dose group was significantly lower(p<0.05). The difference was not significant among model group,low dose group and high dose group(p>0.05).Conclusion: Portal hypertension induced stasis of blood in colon and active factors dilated blood vessel in intestinal canal. Those played an important role in pathogenesy of portal hypertensive colopathy. Angiotonin AT1 type receptor antagonist losartan is protective to the colonic mucosa of PHC in rats because it can reduce colonic submucosal angiectasis and improve colonic mucosal blood supply in rats with PHC. In the other hand losartan can moderately reduce the level of nitrogen monoxidum in serum and relieve congestion in blood vessel. Losartan can reduce the level of TNF-αin scrum. The decrease level of TNF-αmoderates damage of colon in PHC rats and induces decrease of NOS expression in mucosa and submucosa.