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THE EFFECTS OF GARLIC EXTRACT AND ASCORBIC ACID ADMINISTRATION ON MERCURY CHLORIDE-INDUCED CHANGES ON THE HISTOLOGY OF THE KIDNEY OF WISTAR RATS
CHAPTER ONE
INTRODUCTION
1.1 Background of the Study
Mercury intoxication has been a public health problem for many decades. Consideration of the role of environmental factors in determining the susceptibility to mercury has recently been renewed by evidence from epidemiological studies (Wang et al., 2007). Many populations worldwide have been exposed to doses of mercury through the consumption of fishes and other sea foods (Valey et al., 1980; WHO, 2003). Some populations have experienced subsequent neuro-toxic effects and since the epidemic of mercury poisoning from contaminated fish consumption in Minamata, Japan in the late 50s, mercury has been one of the most documented examples of bio-accumulation of toxins in the environment, particularly in the aquatic food chain (ATSDR, 2011). The body accumulates ingested amounts of mercury in the kidney, brain, liver and other tissues including the hair (Burger et al., 2011).
Garlic is a bulbous plant, commonly known as garlic and a species in the onion genus Allium (Woodville, 1793). It is known as one of the oldest horticultural crops in the world (Mottehard, 2015). It is usually obtained as wild or cultivated garlic. The cultivated garlic is mostly referred to as domestic garlic and is the most consumed form which can be gotten from gardens or farmlands.
Garlic is a perennial plant of the lily family, liliaceae, with height up to 1.5m. It has flat leaves of about 8mm wide. It has greenish or whitish flowers, sometimes rosy or not very abundant that stands out with their long peduncle on a head of little bulbs, surrounded by a very long spathe. The bulbs of the garlic are formed by a white cover inside which there are several little bulbs or cloves (Botanical Online, 2015).
There are many different kinds of garlic and they are all different in size, colour, shape, taste and number of cloves per bulb, pungency and storability. There are over 600 cultivated sub-varieties of garlic in the world, although most of them may be selections of only a handful of basic types that have been grown widely and developed their own characteristics over the centuries as local growing condition changed (Anderson et al., 2015). Woodville (1973) reported the botanical classification of garlics as members of lily family and under the species Allium sativum. Two sub-species were postulated Allium sativum, ophioscordon, called ophioscorodon or hard necked garlic, which includes porcelain garlic and recamble garlic. Allium sativum, sativum, or soft necked garlic which includes artichoke garlic, silver skin garlic and cradle garlic. The hard neck garlic was the original garlic and the soft necked ones were developed or cultivated over the centuries by growers from the original hard-necks through a process of selection (Anderson et al., 2015).
Garlic has different names, depending on the area or culture. It is called Eyimsanu in Ibibio, Ayuu in Igbo and Ayo in Yoruba languages of Nigeria (Ndukwu and Ben-Nwadibia 2015). Garlic can be consumed raw, though not palatable, because of its pungent flavor. It can be cooked and used as condiment or as a primary spice (Matthew, 2014). Cooked garlic is a basic component in many dishes in Africa. Theflavor of the garlic often varies based upon its methods of preparation. Raw garlic has the strongest taste and is commonly paired with onion, and ginger, as well as tomatoes (Matthew, 2014). These flavor influenced food from a variety of regions and culinary discipline. Garlic are readily available as pills, capsules, liquid and actual raw cloves (Godwin, 2014).
Curinga, (2015) reported that garlic extract may play a part in protecting against lost of brain function, as indicated by its ability to increase memory, cognitive functions and longevity. He also reported in a study involving Dilly trisultides that it is an effective therapeutic agent in preventing tumour progression and in inducing apoptosis in active human glioblastoma, without impairing liver function.
Vitamin C or ascorbic acid is an essential nutrient for humans and some other animal species. In living organisms ascorbate acts as an antioxidant by protecting the body against oxidative stress (Groff et al., 1995). It is also a cofactor in at least eight enzymatic reactions including several collagen synthesis reactions. Ascorbate is required for a range of essential metabolic reactions in all animals and plants. Ascorbic acid is not synthesized by some species of birds and fish. All species that do not synthesize ascorbate require it in their diet. Deficiency in this vitamin causes the disease scurvy in humans (Mader, 2001; Kumar et al., 2010).
1.2 Statement of the Problem
Mercury is well known as a hazardous metal and its toxicity is a common cause of acute heavy metal poisoning with cases of 3,596 in 1997 by the American Association of Poison Control Centers. Methyl mercury is a neurotoxic compound which is responsible for destruction of microtubules, mitochondrial damage and lipid peroxidation (Patrick, 2002). The total amount of mercury emission into the environment has been assessed at 2,200 metric tons annually (Ferrara et al., 2000). It is estimated that 8 to 10% of American women have mercury levels that would induce disorders in any child they gave birth to, according to both the Environmental Protection Agency and National Academy of Science (Haley, 2005). Rabbits when exposed to 28.8 mg/m3 mercury vapor for 1 to 13 weeks have shown vague pathological changes, marked cellular degeneration and brain necrosis (Ashe et al.,1953).
Mercury can impair any organ and led to malfunctioning of nevers, kidneys and muscles. It can cause disruption to the membrane potential and interrupt with intracellular calcium homeostasis. Mercury binds to freely available thiols as the stability constants are high (Patrick, 2002). Mercury vapors can cause bronchitis, asthma and temporary respiratory problems. Mercury plays a key role in damaging the tertiary and quaternary protein structure and alters the cellular function by attaching to the selenohydryl and sulfhydryl groups which undergo reaction with methyl mercury and hamper the cellular structure. It also intervenes with the process of transcription and translation resulting in the disappearance of ribosomes and eradication of endoplasmic reticulum and the activity of natural killer cells. The cellular integrity is also affected causing free radical formation. The basis for heavy metal chelation is that even though the mercury sulfhydryl bond is stable and divided to surrounding sulfhydryl consisting ligands, it also contributes free sulfhydryl groups to promote metal mobility within the ligands (Bernhoft, 2011).
Mercury is considered the most toxic heavy metal in the environment. Mercury poisoning is referred to as acrodynia or pink disease. Mercury is released into the environment by the activities of various industries such as pharmaceuticals, paper and pulp preservatives, agriculture industry, and chlorine and caustic soda production industry (Morais et al., 2012). Mercury has the ability to combine with other elements and form organic and inorganic mercury. Exposure to elevated levels of metallic, organic and inorganic mercury can damage the brain, kidneys and the developing fetus (Alina et al., 2012). Mercury is present in most foods and beverages in the range <1 to 50 μg/kg. In marine foods it is often seen at higher levels. Organic mercury can easily permeate across the biomembranes and since they are lipophilic in nature, mercury is present in higher concentrations in most species of fatty fish and in the liver of lean fish (Reilly, 2007). Micro-organisms convert the mercury present in soil and water into methyl mercury, a toxin which can accumulate with fish age and with increasing trophic levels. Environmental Protection Agency (EPA) has declared mercuric chloride and methyl mercury to be highly carcinogenic. Exposure to metallic mercury vapors at higher levels for shorter periods of time can lead to lung damage, vomiting, diarrhea, nausea, skin rashes, increased heart rate or blood pressure. Symptoms of organic mercury poisoning include depression, memory problems, tremors, fatigue, headache, hair loss, etc. Since these symptoms are common also in other conditions, it may be difficult to diagnose such cases (Martin and Griswold, 2009). Due to the health effects associated with exposure to mercury, the present standard for drinking water has been set at lower levels of 0.002 mg/L and 0.001 mg/L by the Environmental Protection Act and World Health Organization (WHO, 2004).
A study published in a 2008 issue of the journal “Pharmacological Reports” reveals that garlic can significantly lessen kidney damage associated with mercury chloride exposure in laboratory animals. Mercury chloride used in disinfectants, insecticides, batteries, wood preservatives and other products come in contact with daily is a potential carcinogen, although its effects have not been proven conclusively in humans. Another study in the February 2001 issue of the journal “Food and Chemical Toxicology” points out that low dose of garlic may increase the antioxidant status of kidneys and protect them from free radical-mediated damage. The authors of the study, however, point out that high doses of the herb may have the opposite effect, and thereby emphasizing the need for more research to determine a safe dosage range for garlic.
Vitamin C is a powerful antioxidant that helps to boost the body’s immune system. It is needed for proper growth, development, and to heal wounds. It is used to make the collagen tissue for healthy teeth, gums, blood vessels and bones. Since vitamin C is a powerful antioxidant, it is also used to prevent damage to the bodies from toxicities and pollutants, such as cigarette smoke (Jacob, 1999). Moreover, this research is therefore to investigate the effects of co-administration of mercury chloride, vitamin C and garlic extract on the cyto-achitecutre of the kidney of an albino Wistar rats.
1.3 Significance of the Study
Generally, garlic is used as spice and vitamin C supplement is of great importance in a typical Nigerian home. Garlic is a culinary spice and medicinal herb, having been used throughout recorded history (Godwin, 2014). In traditional African medicine, it also serves many purpose including treatment and prevention of various diseases. It has anti-atherogenic, anti-apoptotic and is neuroprotective (Mathew and Biju, 2008).
Significant exposure to mercury can cause acrodynia involving a pink rash on the extremities, paresthesias and pain (Leong et al., 2003). Thus, with the oxidative properties and ameliorative functions of garlic and vitamin C it is hoped that this work will provide an alternative for the management of mercury exposure.
1.4 Aim and Objectives of the Study
The aim of the study is to observe the effects of garlic extract and ascorbic acid administration on mercury chloride-induced changes on the histology of the kidney of Wistar rats.
The specific objectives are:
- To investigate the effect of garlic extract and ascorbic acid on the body weight of Wistar rats, following mercury chloride administration.
- To investigate the effect of garlic extract and ascorbic acid on mercury chloride-induced changes on the histomorphology of the kidney of Wistar rats.
1.5 Scope of the Study
This work is limited to the effect of garlic extract and ascorbic acid on the histology of Wistar rat as observed under the light microscope.