ABSTRACT
The aim of this study was to investigate the effect(s) of cold water stem bark extract of A. boonei on CCl4-induced liver damage in male rabbits; as well as to ascertain the immunological status of the animals. Twenty (20) animals were divided into 4 groups. Group 1 served as control and was given 1mL/kg body weight of normal saline for 7 days. Group 2 received a single dose of 1mL/kg of CCl4 , while group 3 received 0.5g/kg body weight of extract for 7 days before CCl4 administration. Group 4 received 0.5g/kg body weight of extract for 7 days. Aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, bilirubin, total protein and albumin were determined using standard colorimetric methods. The animals in group 3 did not significantly lose weight (p>0.05), while there was weight loss in groups 2 and 4 (p0.05) in the concentration of plasma and tissue homogenate of conjugated bilirubin, total bilirubin, and alkaline phosphatase activity. Furthermore, there was significant increase (p0.05) except WBC that decrease in group 3 (p>0.05). In group 4, there were decreases in RBC, Hb and HCT (p0.05).The plant extract aggravated toxicity effects in liver function with suppressed immunity. These results portend possible dangers for individuals who may be placed on long term therapy of this extract.
CHAPTER ONE
INTRODUCTION
The liver is the largest internal organ in the body.It weighs about 1.5 kg in an adult human and 0.9kg inrabbits.It is also the most active and most complex organ. Suffice it to say, that, the liver plays a major role in metabolism by independently handling virtually all biochemical transformations. Consequently, the replenishing power of the liver is not in doubt because it carries out inter alia metabolic, secretory, excretory, storage, and detoxification functions (Edet et al., 2011). Needless to say that, the liver is a sine qua non for life.
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Figure 1:Showing the anterior and posterior view of the liver (www.liverpic.com)
Despite its many interesting functions, the liver is prone to suffer a lot of damage.
These damages give rise to various forms of liver diseases. The end result is that the liver malfunctions and its efficacy in carrying out its functions is hampered. There exists a myriad of liver diseases such as alcohol liver disease, hepatic cirrhosis, hepatocellular carcinoma, haemochromatosis, autoimmune hepatitis, fulminant hepatitis, hepatic encephalopathy, etc.
These defects in liver function could have implications on other organs. For instance, acute liver failure correlates with acute renal failure with an approximately 55% frequency of occurrence, although the relationship between cirrhosis and renal dysfunction has not been fully established (Jaramillo-Juarez et al., 2008). The defects in liver function could be as a result of alcohol, drugs (acetaminophen), chemical compounds (e.g. thioacetamide, carbon tetrachloride) etc.
1.1Carbon Tetrachloride
Carbon tetrachloride (also known as carbon tet, with IUPAC name: tetra chloromethane) is an organic compound with the chemical formula CCl4. It has adverse health effects because of its toxicity. Researchers have shown that CCl4 is one of the most potent toxins; especially, those of hepatic forms. This explains its wide usage in experimental models for the evaluation of the abilities of hepatoprotective agents (Seifert et al., 1994). CCl4-induced hepatic damage is principally caused by lipid peroxidation and decreased activities of antioxidant enzymes. This gives rise to the generation of free radicals (Shahjahan et al., 2004). These effects could however be mitigated by hepatoprotective agents. These hepatoprotective agents are usually common medicinal plants.(Etim et al., 2008).
1.1.1 Physical And Chemical Properties
Description:Colourless liquid
Molecular formula:CC14
Molecular Weight:153.8g/mol
Density:1.59g/cm3 @ 20oCBoiling point:76.7oC
Melting point:-23oC
Vapour pressure:91.3 torr @ 20oC
Solubility: Soluble in acetone, ethanol, benzene, carbon disulfide, slightly soluble in water.(HSDB, 1995; CRC, 1994).
1.1.2Natural Occurrence Of Ccl4
There are suggestions that carbon tetrachloride can be formed in the troposphere by the photochemical reactions of chlorinated alkenes that are solar-induced (Singh et al., 1975). However, this reaction has so far remained solely laboratory-based since it can only be demonstrated in the laboratory. Even if it could happen in nature, there are indications that it would not be a major source of environmental carbon tetrachloride. Also, Carbon tetrachloride has been detected in volcanic emission gases (Isidorov et al., 1990). Several other studies have postulated that global atmospheric levels of carbon tetrachloride can be clearly explained by anthropogenic sources alone (Singh et al., 1976). This implies that humans are major determining factors in CCl4 concentration and pollution in the world.
1.1.3Environmental Occurrence Of Ccl4
The major source of carbon tetrachloride in air is industrial emissions. It has also been detected in surface water, groundwater and drinking-water. This is due to industrial and agricultural activities. The occurrence of carbon tetrachloride has also been reported in wastewater arising from iron and steel manufacturing, foundries, metal finishing, paint and ink formulations, petroleum refining and nonferrous metal manufacturing industries (United States National Library of Medicine, 1997).
1.1.4Uses Of Ccl4
A large percentage of the carbon tetrachloride produced is principally used in the production of Chlorofluorocarbons (CFCs). These CFCs are primarily used as refrigerants, propellants, foam-blowing agents and solvents and in the production of other chlorinated hydrocarbons. Carbon tetrachloride has also found wide usage as a grain fumigant, pesticide, solvent for oils and fats, metal degreaser, fire extinguisher and flame retardant, and in the production of paint, ink, plastics, semi-conductors and petrol additives. Carbon tetrachloride also found wide usage previously as a cleaning agent. However, these many uses have apparently phased-out since production has dropped (ATSDR, 1994). The drop in production in recent years is due to the Copenhagen Amendment to the Montreal Protocol (1992) (UNEP, 1996). Furthermore, carbon tetrachloride is a known and potent hepatotoxin, hence its wide usage in experimental models for the evaluation of the properties of hepatoprotective agents (Seifert et al., 1994). This justifies the central position it occupies in this study.
1.2Mechanism Of Carbon Tetrachloride Induced Toxicity
It has been reported that the cytochrome P-450-dependent monoxygenase system is a principal site responsible for carbon tetrachloride reductive metabolism (Wolf et al., 1980). In the study of CCl4 metabolism, a great emphasis is placed on the involvement of covalent binding of CCl4 metabolites to cell components and/or peroxidative damage as the cause of injury. Binding has been reported to occur preferentially to triacylglycerols and phospholipids, with phosphatidylcholine containing the highest amount of binding. CCl4 is also known to decrease the rate of triacylglycerol secretion as very low density lipoproteins (Boll et al., 2001).
A very early investigation has already suggested that carbon tetrachloride toxicity depends on cleavage of the carbon-to-chlorine bond (C-Cl bond). There is also a very strong and established link between the metabolism of carbon tetrachloride and the peroxidative decomposition of cytoplasmic membrane structural lipids (Recknagel, 1967).