HISTOPL4THOLOG1CAL STUDY OF LIVER

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1 HISTOPL4THOLOG1CAL STUDY OF LIVER 6.1 Inti-oduction The structural and functional organization of the liver has been described by hepatic lobule and hepatic acinus models, respectively (Jarvelainen, 2000). The hepatic lobule is defined histologically as a hexagonal region of parenchyma which surrounds the central vein at its centre. The hepatic lobules are composed of one-cell thick parenchymal cell plates, arranged radially around the central vein, thus forming sinusoidal blood spaces. According to the lobular concept, the blood flows from the periphery of the lobule, i.e., from the portal vein and hepatic artery, through sinusoids, and into the central veins. Hepatic acinus is defined as the smallest structural and functional unit in the liver, a term based on the microcirculation in the liver. The simple hepatic acinus is defined as a parenchymal mass organised around the portal triad (Fig l), with the portal triad consisting of bile ductules, branches of the portal vein and branches of the hepatic artery. Within the acinus, blood drains from the portal triad through the sinusoids into the central hepatic vein. The cells of the ' acinus are arbitrarily divided into three zones: the periportal zone, the intermediate zone and the perivenular zone. The blood supply is mainly from the portal tract vessels: 80% from branches of the portal vein and 20% from the hepatic artery

2 Fig The hepatic acinus - the functional unit of liver. Blood drains from the tii~al branches of the terlninal portal venule (TPV) and hepatic arteriole (HA) in zone 1. to the ternlinal hepatic venule (THV) in zone 3 (from Jarvelainen, 2000) Five intrinsic cell types have been identified in the liver: the parenchymal cells or hepatocytes and four types of non-parenchymal cells. The nonparenchymal cells are the liver resident macrophages; the Kupffer cells; endothelial cells; the Stellate cells (also called Ito - or fat storing cells) and the pit cells or large granular lymphocytes. In the rat. hepatocytes represent for about 60% of the total cell number and 80% of hepatic tissue volume. 1njui-y to the parenchymatous organs particularly to the liver due to various chernical agents is well documented. They are used as popular experimental tools for the investigation of liver injury. The liver damage produced by these agents is seen shortly after the exposure to the toxic substances and is dose related. The microscopic lesions produced are usually fatty metamorphosis, centrizonal necrosis and are reproducible in a variety of animal species (Rao, 1973). In rats, administration of a single dose of carbon tetrachloride produces reversible perivenular hepatocyte damage, resembling the picture seen in man following paracetamol overdose. The perivenular region is located furthest from the portal. area. the entry site for oxygen-rich blood. As the concentration of

3 oxygen is often lower in the tissue's downstream region, the perivenous cells in the liver are potentially more susceptible to ischemic necrosis. After hepatotoxin treatment. hypoxic conditions sufficient to damage hepatocytes may develop in this area. Furthermore, the expression of CYP2El which is highest in the perivenular region, produces oxy-radicals that contribute to the injury (Kato et al., 1990). Moreover, hepatocytes in the perivenous area contain less antioxidant factors and antioxidant enzymes (Kera et al., 1987). Thus, while the lipid \ peroxidation mediated by oxy-radicals is likely to be highest in the perivenous area, the detoxifying capacity of hepatocytes here is reduced; therefore, the production may exceed the detoxification specifically in the perivenular area. This is importailt in liver toxicity induced by xenobiotics. Xenobiotics that cause liver injury have to be preactivated by 1997). enzymes in order to cause injury (Lieber, Alterations involving the endoplasmic reticulum of parenchymal cells of rat liver have also been reported during carbon tetrachloride poisoning (Reynolds and Ree, 1971). Recovery to pre-injury histological appearances occurs with some production of extracellular matrix proteins during the healing phase (Johnson et al., 1992). This therefore represents a suitable model for the study of the protective effect of medicinal plants. As G.glabra root powder exhibited the highest degree of antiperoxidative activity, it was selected for the histopathological study. 6.2 Materials and Methods Male albino rats of Sprague-Dawley strain were used for the experiment. All other experimental details are as given in chapter 3 of materials and methods. 6.3 Results and Discussion Results of the histopatl~ological examination of liver in pairfed control, CC14-treated and CC14 + G.glabra treated rats are given in the table 6.1.

4 Table 6.1 I-Tistopathological changes of liver Group I - Pairfed control ~- - Histopathological changes Hepatocyte lobule 1 Architecture 1 Central vein I Portal triad Normal I Normal I Normal I Nonnal I1 - CC1,- treated Fatty change, pan lobular ballooning degeneration Distorted with nodule formation Distorted Fibrous portal expansion, moderate fibrosis and I inflammation Normal, some hepatocytes show mild fatty change and ballooning degeneration Mild distortion ' ~ o i a l Mild fibrosis with inflammation

5 Big Photomicmgraphs of liver section taken hm normal control rats. (a): sbwing central vein ad portal triad munded by nod hepatocytes. (Hematoxylin and Eosin. x 100); (b): an enlarged view of (a) showing normal central vein summded by normal hqmbcyb (Hemataxylin and Eosin. x 200)

6 ' Fig. 633 Photomicrographs of liver section taken from CC14: liquid pamflintreated rats (a): showing portal triad with moderate fibrosis, inflammation and hepatooytes with fatty cbange and ballkniug degeneration (Hematoxylin and Edn x 200); (b): showing dilated central vein and hepa- with fatty change and ballooning degendon (Hanatoxylin and Eosin. x 200).

7 Fig 633 Photomimgraphs of liver section taken from CC14: liquid paraffin, and Glycyrrhiza glabra (roots) - treated rats. (a): showing central vein and and portal triad with normal hepatic cells. (?iematoxylin and Eosin. x 100); (b): another vim of (a) showing centrai vein and normal heptocytes with occasional hepatocytes showing fatty change and ballooning degeneration (Hematoxylin and Eosin. x 100).

8 Liver slices of normal rats showed normal hepatic architecture and no fatty changes (Fig ). Administration of CCI4-liquid paraffin (0.3 ml CC14 in liquid paraffin. 3:l. viv!100 g body weight) resulted in fatty change and lobular balloonir~g degeneration of hepatocytes. The liver showed distorted architecture with nodule formation, distorted central vein and the portal triad showed fibrous portal expansion with moderate fibrosis and moderate inflammation (Fig ). Administration of the root powder of G.glabra at a dose of 1000 mglkg body weight exhibited significant improvement (Fig ). The hepatocytes showed only mild fatty change. The liver showed only mildly distorted architecture. Central vein showed no distinct changes. Portal triad exhibited only mild fibrosis with mild inflammation. Histological observations basically supported the results obtained from the other biochemical investigations (experiments and 3.3.3). Histological profile of the liver from CC1,-liquid paraffin-treated rats has been reported to show intense centrilobular necrosis, steatosis, swelling of hepatic cytoplasm (Bhakta el al., 1999), ballooning degeneration, fatty changes and broad infiltration of lymphocytes and Kupffer cells around the central vein (Lin el al., 1998). The protective effect of G.glahra may partly or solely be due to the possible antioxidant property of the plant. The mechanism of action of the plant remains to be studied. The above results support the incorporation of G.glabra as a component in many polyher-bal preparations in indigenous medicine. It can also be suggested that the protection offered by Kamilari in CC1,-induced hepatic dysfunction in rats may b; due to the presence of G.glabra as one of the ingredients.