Effects Of Vitamin C On Some Haematological Parameters And Biomarkers Of Oxidative Stress In Albino Wistar Rats Exposed To Short-Term Lead Acetate
The effects of vitamin C on some heamatological parameters and biomarkers of oxidative stress in albino wistar rats exposed to lead acetate over a short term (3 weeks) was investigated. Studies have revealed that lead has a wide range of health effects that can result from exposure, and that lead can cause health effects at blood lead levels previously thought to be safe. An increasing body of evidence suggests that lead is associated with a number of health conditions. Twenty albino wistar rats were randomly divided into four experimental groups of five rats each, Control group were fed normal rat feed with distilled water, Group 2,3 and 4 were fed normal rat feed, water and received daily oral administration of lead acetate 250mg/kg daily. In addition groups 3 and 4 received 100mg/kg and 150mg/kg oral administration of vitamin C respectively, for three weeks. Mild effect of lead acetate was observed in haematological parameters as indicated by slightly increase ,which was not statistically significant, in RBC and MPV. In contrast, a slight decrease was seen in haemoglobin, PCV, MCV, MCH, MCHC and platelet count. Decreases in MCV,MCH and MCHC indicated shrink in size of RBCs and onset of microcytic anemia due to onset of iron deficiency. However, decrease observed was not statistically significant. Also the effect of lead acetate was mild on biochemical enzyme activities, indicated by increased level of MDA activity; which indicate oxidative stress, however the increase was not statistically significant. SOD and GPx level were slightly decreased, which was not statistically significant. The doses of vitamin C supplement did not reverse the effect of lead acetate on some haematological parameters and some biochemical enzyme activities, it however reverse the effect of lead acetate on MDA level. In conclusion, exposure to lead acetate over a short term has little effect on haematological parameters and biochemical enzyme activities. The doses of vitamin C use in this study has ameliorative effect on MDA activity but has no effect on some alteration on haematological parameters and some biochemical enzyme activities.
1.1 General Introduction
Lead is a naturally occurring bluish-gray heavy metal found in small amounts in the earth‟s crust. However, it is rarely found naturally as a metal. It is usually found combined with two or more other elements to form lead compounds (ATSDR, 2007). Metallic lead is resistant to corrosion (i.e., not easily attacked by air or water). When exposed to air or water, thin films of lead compounds are formed that protect the metal from further attack (ATSDR, 2007). Lead is poisonous when inhaled or eaten. Lead content in air, food and tap water has increased several folds during recent years due to extensive use of this metal in petrol, paints, battery and other industries (Tuarmaa, 1995). According to WHO (2000) lead is a metal with no known biological benefit to humans. Too much lead can damage various systems of the body including the nervous and reproductive systems and the kidney.
Generally, heavy metals produce their toxicity by forming complexes or ligands with organic compounds thereby affecting the function of biological molecules, inactivate some biochemical enzymes and affect protein structure (Pirkle, 1998) Because of its potential health problems, the amount of lead used in these products today has lessened or has been removed. Lead and other heavy metals create reactive radicals which damage cell structure including DNA and cell membrane (Flora, 2008). Lead poisoning can cause a variety of symptoms and signs which vary depending on the individual and the duration of lead exposure (Kosnett, 2005, Karri, 2008 ).
The amount of lead in blood and tissues, as well as the time course of exposure, determines the level of toxicity (Pearson and Schonfeld, 2003).
The absorbed lead enters the blood stream where over 90 percent of it is bound to the red cells with a biological half life of 25-28 days (Azar, 1975). Toicological effects of lead have their origin in perturbation in cell function of various organ systems. The major biochemical effect of lead is its interference with heme synthesis which leads to haematological damage (Awad and William, 1997). Impaired synthesis of heme interfers with oxygen transportation to the tissue. Lead interferes with the production of heme at several different steps. Lead exposed persons can develop anaemia. In adults, anaemia is usually seen in severe chronic lead poisoning and blood lead levels of 70 µg/dL and higher are usually found (Gulson and Salome, 1996). Animal models exposed to lead show significant changes in haematological parameters (Ashour, 2006) Gulson and Salome (1996) stated that lead is a cumulative poison. Unlike acute poisons, such as chemicals that can kill quickly by attacking the lungs, lead poisoning happens slowly. The lead that is taken in daily, mounts up in the tissues, especially the bones. Blood lead levels mainly show recent exposure, however; lead that is removed from bone is also present in the blood. It is quite possible for higher amount of lead in the body than the blood lead level.
Vitamin C is a water-soluble micronutrient required for multiple biological functions (Halliwell, 2001). It is found intra- and extracellularly as ascorbate, and is well absorbed from the gastrointestinal tract (Chihuailaf, 2002; Woollard, 2002; Asiley, 2004). Vitamin C is a natural antioxidant that prevents the increase production of free radicals induced by oxidative damage to lipids and lipoproteins in various cellular compartments and tissues (Sies,1992).
The antioxidant function of vitamin C is related to its reversible oxidation and reduction characteristics. Thus, vitamin C may particularly prevent certain types of hepatic cellular damage (McDowell, 1989; Parola, 1992; Sies, 1992; Burtis and Ashwood, 1994).According to Patrick, (2006a) consumption of 100 mg of vitamin C a day has been shown to significantly decrease lead levels in some, though not all, cases – apparently more through reduced absorption rather than increased excretion. Vitamin C has been consistently shown to protect the concentration of molecules such as ALA dehydratase that are associated with red blood cell manufacture. Vitamin C improves iron absorption; it can mix with food in the stomach, as well as increasing iron‟s capacity to displace lead during food absorption. There is some evidence that Vitamin C can inhibit lead uptake at a cellular level as well as lead‟s cellular toxicity. Experiments with rats have demonstrated reduced lead impacts on a variety of body organs.
1.2 Statement of Research Problem
Lead exposure remains one of the most important problems in terms of prevalence of exposure and public health impact (Hu et al., 2006). Worldwide, lead poisoning accounts for nearly 1% of the global burden of disease (Landrigan and Ayuso-Mateos, 2004). Despite decades of intensive research, lead poisoning remains one of the most, if not the most, studied subjects of all within the fields of environmental health and environmental medicine (Hu et al., 2006).Lead exposure occurs via four basic media: food, dust or dirt/soil, air and water and mostly via two routes, inhalation and ingestion. Mushak and Crocetti (1996) have reported on the large body of literature showing that deficiencies or alterations in essential nutrients like calcium, iron, phosphorus and zinc enhance lead exposure and increase the degree of lead toxicity associated with such exposure.
Cells absorb lead through the same channels they absorb calcium from. The drugs that regulate the intake of calcium also increase the amount of lead uptake. High levels of lead decrease transport of calcium and vice versa, therefore these two metals function as competitive inhibitors. Lead can enter through the same ion channels as calcium and regulate the activity of those channels to uptake more lead into the cell (Patel, 2000).
Epidemiological studies and clinical observations provide evidence for a progression of adverse health effects of lead in humans that occur in association with blood lead ranging from <10 to >60 μg/dL (ATSDR, 2007). Over the past century in particular, increasingly sophisticated epidemiological studies have more adequately revealed the wide range of health effects that can result from exposure to lead, and that lead can cause health effects at blood lead levels previously thought to be safe. An increasing body of evidence suggests that lead is associated with a number of health conditions (Schafer et al., 2005).
Lead has long been known to alter the hematological system. At the low end of the blood lead concentration range, adverse effects include increased blood pressure and inhibition of pathways in heme synthesis. The anemia induced by lead results primarily from both inhibition of heme synthesis and shortening of the erythrocyte lifespan (ATSDR, 2007). In most cases the symptoms of lead are misdiagnosed and people are unaware of the damage that can be caused by lead. It recent years more attention and research has been directed towards lead poisoning and its effect on the human body but little has been done to access its effect on hematological parameters and anti oxidadant emzyme activities.
There has been an increasing incidence of lead poisoning all over the world. Despite the attempt for reducing the exposure to this metal, there is still some report of cases of severe lead toxicity (Hershko, 2005; Roch , 2005; Coyle 2008) . According to Escribano (1997) 140 mg/kg dose was an approximate environmental daily-exposure level.The effects of low-level lead poisoning in children may be irreversible and there may be no threshold for health effects. Numerous risk factors predispose children to both higher exposure and greater vulnerability to the hazards of lead.
Children in low-income countries are usually at elevated risk of exposure to lead, involving multiple sources and higher levels of exposure than observed in high-income countries (Nriagu et al., 1996). African children, in particular, may be at high risk of lead exposure and poisoning as a consequence of a paucity of information available to the public on the sources and mechanisms of exposure to lead in children, ongoing use of lead in many products, inadequate regulatory frameworks, weak enforcement of existing legislation, high levelsof poverty and inequity, poor housing conditions and extensive malnutrition (Nriagu et al., 1996; Tong et al., 2000).
Studies conducted at mines around the world have shown that children living in close proximity to a mine may be at increased risk of lead exposure (Lyle et al., 2006; von Schirnding et al., 2003).More than 400 children have died in five villages, most of them under three years of age from lead poisoning in Zamfara state, Nigeria (Grossman, 2012),
According to WBG, (1996) lead is found frequently in our environment and in our body, it has no known purpose in the body. In developing nations, massive lead contamination is occurring from the continued use of leaded gasoline. Lead levels along roads in Nigeria approach 7000 parts per million, about 15 times higher than the level used to designate a toxic Superfund Site in the U.S. In Mexico City, half the children tested have dangerous levels of lead in their blood and in Cairo, more than 300 infants die annually due to maternal lead exposure(WBG, 1996).
With the wide occurrence of lead poisoning in both developed and developing nations from food, drinks and contaminated soil, it is therefore necessary to assess the effect of lead poisoning on haematological parameters and biomarkers of oxidative stress and assess the beneficial effect of Vitamin C in reversing the effect of lead on haematological parameters and biomarkers of oxidative stress since they are used to measure physiological disturbance and level of damage cause by disease or toxic substance to the body.
The aim of this study is to investigate effect of vitamin C on some haematological parameters and biomarkers of oxidative stress in albino Wistar rats exposed to short term lead acetate.
- To evaluate the effect of short-term vitamin C-lead acetate exposure on haematological parameters such as RBC, , Hb, MCV, MCH, MCHC, MPV,platelets count in albino Wistar rats
- To evaluate the effect of short-term vitamin C-leadacetate exposure on MDA, SOD and GPxactivity in albino Wistar rats.
1.6 Null Hypothesis
Vitamin C has no effect on haematological parameters and biomarkers of oxidative stress in albino wistar rats exposure to lead acetate.
5.0 Summary, Conclusion and Recommendation
After three weeks of administration,animals were sacrificed and blood samples collected via cardiac puncture. Haematological parameters were analysed which include RBC, WBC,Hb, MCV, MCH, MCHC, MPV, biochemical parameters which include MDA, SOD and GPx were also analysed. The result indicated no significant changes in haematological parameters, however, RBC count slightly increased in lead acetate treated rats which could be due to the slight decrease in hemoglobin production because of lead induced disturbance of heme biosynthesis.Decrease in Hb, PCV, MCV, MCHC, PLT was also observed which indicate onset of microlytic anaemia, however, the effect of lead on haematological parameters was not reversed by vitamin C administration concurrent with lead acetate. The lack of ameliorative effect of vitamin C on haematological parameters and antioxidant enzymes SOD and GPx could be due to low concentration of vitamin C a result of low dose used in the study, hence decreased absorption of vitamin C by RBC or due to a maximum uptake of vitamin C by other peripheral tissues. The effect of lead on antioxidant system was reflected in the increase of MDA, SOD and GPx were slightly decreased. Lipid peroxidation is considered a serious consequence of free radical toxicity, free radicals generate a cascade of reactions which induce lipid peroxidation. The increases in MDA level indicate oxidative stress. However, the doses of vitamin C used in this study did not ameliorate the alterations caused by the effect of lead on haematological parameters but reserved the effect of lead on MDA, the effect of lead on SOD and GPx were not reversed by vitamin C supplement.
Result obtained on the effect of vitamin C and short term low lead exposure on haematological parameters under the present investigation generally show no statistically significant changes.In conclusion the present study showed that lead acetate induced hematological changes were not significant after short term exposure and dose of vitamin C administrated did not effect in the improvement of impaired parameters affected by lead acetate exposure.
Low dose short term lead acetate administration induced oxidative stress by increasing the level of MDA, however SOD and GPx level did not show much effect. Dose of vitamin C used in this study doesnot have ameliorative effect on changes induced by low lead exposure on heamatological parameters and antioxidant enzyme activity but vitamin C reversed the effect of lead on lipid peroxidation.
- Additional research priorties should include the effort to assess the anti oxidant effect of vitamin C at higher dose.
- Additional research should be directed towards assessing the effect of lead exposure at longer terms.
- Further work is needed to find the effective and safe intervention for lowering the lead exposure at the general population level to prevent consequence of exposure.
- Efficacy of specific intervention to keep blood lead concentration below reference level.
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