الفهرس 
Proliferating cell nuclear antigen (PCNAOnly 14 pages are availabe for public view
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Abstract
fibrosis can be considered as a dynamic and highly integrated cellular response to chronic liver injury. Whatever the etiology, the evolution of chronic liver damage is characterized by perpetuation of parenchymal necrosis, hepatitis and qualitative as well as quantitative alterations .
Silymarin treatment in vivo was found to be effective in preventing or reducing liver fibrosis. The current study was designed to investigate the protective effect of silymarin on CCl4 hepatotoxicity of male Sprague-Dawley mature rats. The animals were divided into three groups: group I, of animals used as normal control, group II of animals, received an intraperitoneal injection of 1.0 ml/kg body weight of 10 % CCl4 dissolved in olive oil 3 times a week for 12 weeks and group III of animals, received CCl4 as in group II and treated with a daily oral dose of 50 mg/kg silymarin for 12 weeks.
I - Histopathological results :
1-Hematoxylin and Eosin stains:
Hematoxylin and Eosin stains were used for histopathologial study of rats liver after injection of CCl4. The liver sections showed necrosis, ballooning degeneration and severe vacuolization, in addition to dilation and congestion of sinusoids and portal veins. The portal areas also showed gradual increase in inflammatory cellular infiltration that reached a marked degree with portal fibrosis after 12 weeks of CCl4 injection .
These alterations were almost recovered by silymarin treatment most of the hepatocytes regained nearly their normal appearance except for few remaining degenerated cells with minimal portal inflammation and slightly dilated sinusoids. This may point out the hepatoprotective effect of silymarin against the highly reactive free radicals and lipid peroxidation induced by CCl4.
2- Reticulin stain :
Gordon and Sweet’s technique was used to demonstrate the reticular fibers in rat liver tissue. These fibers were normally distributed as a meshwork supporting the liver tissue. Condensed fibers were increased gradually around the portal areas with expansion of excessive reticulin to form fibrous septa. After 12 weeks of CCl4 injection it reached great expansion in the portal areas associated with porto-portal bridging fibrosis.
In CCl4-Silymarin treated groups the fibrosis was resolved except for only one portal tract that showed mild fibrosis after 12 weeks of treatment suggesting the antifibrotic role of silymarin.
3-Toluidine blue stain
Mast cells were demonstrated in liver tissue using toluidine blue stain. It was found that the numbers of mast cells increased gradually by the time of CCl4 injection. However, CCl4-Silymarin treated animals showed significantly decreased numbers of mast cells as compared to CCl4 groups which reflected the ability of silymarin as a stabilizer of the mast cells.
II- Histochemical result:
- Periodic acid Schiff’s (PAS) :
Periodic acid Schiff’s reagent was used to demonstrate glycogen content in liver cells. It was appeared as red-purple colored granules diffusely distributed throughout the cytoplasm. Gradual decrease in glycogen content was noted in CCl4 injected rats to reach a remarkable decrease after 12 weeks whereas, in CCl4.-Silymarin treated group the majority of hepatocytes regained nearly its normal glycogen content.
III- Immunohistochemical results:
PCNA immunostaining technique was used to evaluate the proliferative activity of hepatocytes. Normally few PCNA positive hepatocytes were found in normal liver tissue. The expression of PCNA was increased upon CCl4 injection indicating that hepatocytes exhibited high replicative activity in response to chronic liver injury and it was time dependant.
In silymarin treated groups, significant increase in the expression of PCNA indicating the role of silymarin in liver regeneration, as shown by an increased number of mitotic figures .
IV- Biochemical results:
Serum biomarkers, AST and ALT levels were increased significantly in a time dependant fashion in CCl4 group compared to controls. These findings indicated that CCl4 injection resulted in severe damage of hepatocytes with the release of the cytosolic and mitochondrial enzymes into the blood stream. On the other hand, silymarin treatment significantly reduced the elevated levels of circulating AST and ALT compared to CCl4 group suggesting the ability of silymarin in preserving the cell membrane integrity.