Arsenic contamination

1.1 Overview

Arsenic contamination of groundwater is natural and found in high

concentrations in deeper levels of groundwater. It is a high-profile problem due

to the use of deep tubewells for water supply in the Ganges Delta, causing

serious arsenic poisoning to large numbers of people. A 2007 study found that

over 137 million people in more than 70 countries are probably affected by

arsenic poisoning of drinking water.

Arsenic contamination of the groundwater in Bangladesh is a serious problem.

Prior to the 1970s, Bangladesh had one of the highest infant mortality rates in

the world. Ineffective water purification and sewage systems as well as periodic

monsoons and flooding exacerbated these problems. As a solution, UNICEF

and the World Bank advocated the use of wells to tap into deeper groundwater.

Millions of wells were constructed as a result. Because of this action, infant

mortality and diarrheal illness were reduced by fifty percent. However, with

over 8 million wells constructed, approximately one in five of these wells is

now contaminated with arsenic above the government's drinking water standard.

In the Ganges Delta, the affected wells are typically more than 20m and less

than 100m deep. Groundwater closer to the surface typically has spent a shorter

time in the ground, therefore likely absorbing a lower concentration of arsenic;

water deeper than 100m is exposed too much older sediments which have

already been depleted of arsenic.

The crisis came to international attention in 1995. The study conducted in

Bangladesh involved the analysis of thousands of water samples as well as hair,

nail, and urine samples. They found 900 villages with arsenic above the

government limit.

The acceptable level as defined by WHO for maximum concentrations of

arsenic in safe drinking water is 0.01 mg/L. The Bangladesh government's

standard is at a slightly higher rate, at 0.05 mg/L being considered safe. In

Bangladesh, 27% of shallow tube-wells have been shown to have high levels of

arsenic (above 0.05mg/l). It has been estimated that 35 - 77 million of the total

population of 125 million of Bangladesh are at risk of drinking contaminated

water (WHO bulletin, volume 78, page 1096). Approximately 1 in 100 people

who drink water containing 0.05 mg arsenic per liter or more for a long period

may eventually die from arsenic related cancers.

Arsenic is a well-recognized human carcinogen. Its exposure was shown to

depress the antioxidant defense system leading to oxidative damage to cellular

macromolecules including DNA, proteins, lipids(Shi et al. 2004), wreak havoc

in biological system by tissue damage, altering biochemical compounds and

corroding cell membranes (Wiseman & Halliwell 1996). Though liver appears

to be the main target of arsenic (Ferrini et al. 1997 & Runge et al. 2004),

kidney, and spleen are also vulnerable to arsenic toxicity (Siewicki, T.C. 2008).

Inorganic arsenic acts as a tumor promoter through reactive oxygen

species (ROS) generation in mammalian cells resulting in oxidative stress

(Garcia-Chavez, 2003) and carcinogenesis in man (Ahmad et al. 2000).

Arsenicosis is the effect of arsenic poisoning, usually over a long period such as

from 5 to 20 years. Long-term exposure to arsenic contaminated water causes a

wide range of adverse health effects, including skin lesions like raindrop

pigmentation, hyper pigmentation, keratosis of skin; anemia, vascular diseases,

conjunctivitis in the eyes, neuropathy, lung diseases and non-melanocytic

cancer of skin and different internal organs. But absorption of arsenic through

the skin is minimal and thus hand-washing, bathing, laundry, etc. with water

containing arsenic do not pose human health risks.

Intermittent incidents of arsenic contamination in groundwater can arise both

naturally and industrially. The natural occurrence of arsenic in groundwater is

directly related to the arsenic complexes present in soils. Arsenic can liberate

from these complexes under some circumstances. Since arsenic in soils is

highly mobile, once it is liberated, it results in possible groundwater

contamination

Arsenic poisoning is treated by some thiol containing chelating agents. They

can be administered either alone or in combination with antioxidants. But the

clinical applications of these chelators cause side effects include

hepatotoxicity, renal toxicity, headache, nausea, vomiting, blood pressure

lachrymation, profuse sweating, intense pain in the chest and abdomen

and anxiety, gastrointestinal discomfort, skin reaction, mild neutropenia etc.

Bangladesh is now facing a serious problem in dealing with a huge number of

patients generated by high level of arsenic exposure. A cheap, available,

ready to make drug/ drug components with negligible or no side-effect is

needed to be found very urgently.

Objectives of this present study:

1. To observe the changes in blood serum parameters of mice exposed to

arsenic.

2. To observe the effects of arsenic in causing damage of chromosomal

DNA.

3. To get help for possible remedy by understanding arsenic toxicity in mice.

1.2 Global Perspective of Arsenic Contamination

Arsenic in drinking water has been detected at concentration greater than the

Guideline Value, 0.01 mg/L or the prevailing national standard in many

countries of the world. These include Argentina, Australia, Bangladesh, Chile,

China, Hungary, India, Mexico, Peru, Thailand, and the United States of

America. Countries where adverse health effects have been documented include

Taiwan, Bangladesh, Mongolia, India (West Bengal), and the United States of

America. Examples are: Arsenic contamination in Taiwan was reported since

1968. A disease called ‘black foot disease’ spread in the country massively.

Later it was known that the cause of the disease was arsenic received through

contaminated tube-well water. Environment Protection Agency of the United

States of America has estimated that some 13 million of the population of

USA, mostly in the western states, are exposed to arsenic in drinking water.

0.045 mg/l of arsenic was found in California’s ground water while 0.092

mg/l in Nevada.

Seven of 16 districts of West Bengal have been reported to have ground water

arsenic concentrations above 0.05 mg/L; the total population in these seven

districts is over 34 million (Mandal et al 1995) and it has been estimated that

the population actually using arsenic-rich water is more than 1 million (above

0.05 mg/L) and is 1.3 million (above 0.01 mg/L).

Figure 1. Groundwater arsenic contamination areas.

1.3 Bangladesh Perspective of Arsenic Contamination

Groundwater arsenic contamination in Bangladesh is reported to be the biggest

arsenic calamity in the world in terms of the affected population. The

Government of Bangladesh has addressed it as a national disaster. Arsenic

contamination of groundwater in Bangladesh was first detected in 1993(Khan et

al. 19997). Recent studies in Bangladesh indicate that the groundwater is

severely contaminated with arsenic above the maximum permissible limit of

drinking water. In 1996, altogether 400 measurements were conducted in

Bangladesh. Arsenic concentrations in about half of the measurements were

above the maximum permissible level of 0.05 mg/l in Bangladesh. In 1998,

British Geological Survey (BGS) collected 2022 water samples from 41 arsenic-

affected districts. Laboratory tests revealed that 35% of these water samples

were found to have arsenic concentrations above 0.05 mg/l.

The experts from Bangladesh Council for Scientific and Industrial Research

(BCSIR) have been found the highest level of arsenic contamination, 14 mg/l of

shallow tube-well water in Pabna (Flora et al. 2004). The recent statistics on

arsenic contamination indicate that 59 out of 64 districts of Bangladesh have

been affected by arsenic contamination. Approximately, arsenic has

contaminated the ground water in 85% of the total area of Bangladesh and about

75 million people are at risk (Flora et al. 2005). It has been estimated that at

least 1.2 million people are exposed to arsenic poisoning. The reported number

of patients seriously affected by arsenic in drinking water has now risen to

8500(Nandi et al. 2005). As the people are getting arsenic also from food chain

such as rice, fish and vegetables, the problem is growing more severe. The

current statistics of arsenic calamity given in Table 1 present the severity of

arsenic contamination in Bangladesh.

Table 1: Statistics of Arsenic Calamity in Bangladesh (Flora et al. 2005)

Total Number of Districts in Bangladesh 64Total Area of Bangladesh 148,393 km2Total Population of Bangladesh 125 millionWHO Arsenic Drinking Water Standard 0.01 mg/l

Bangladesh Arsenic Drinking Water Standard 0.05 mg/lNumber of Districts Surveyed for Arsenic Contamination 64Number of Districts Having Arsenic above 0.05 mg/l inGroundwater

59

Area of Affected 59 Districts 126,134 km2Population at Risk 75 millionPotentially Exposed Population 24 millionNumber of Patients Suffering from Arsenicosis 8,500Total Number of Tube-wells in Bangladesh 4 millionTotal Number of Affected Tube-wells 1.12 million

1.4 Mechanism of arsenic contamination

The large-scale withdrawal of groundwater has caused rapid diffusion of

oxygen within the pore spaces of sediments as well as an increase in dissolved

oxygen in the upper part of groundwater (Figure 1). The newly introduced

oxygen oxidizes the arseno- pyrite and forms hydrated iron arsenate compound

known as pitticite in presence of water. This is very soft and water-soluble

compound. The light pressures of tube-well water break the pitticite layer into

fine particles and make it readily soluble in water. Then it seeps like drops of

tea from the teabag and percolates from the subsoil into the water table. Hence,

when the tube-well is in operation, it comes out with the extracted water. This

mechanism is portrayed in Figure 2.

Figure 2: Mechanism of arsenic contamination in groundwater around a tube-well

1.5 Source of arsenic in ground water

Arsenic ranks 20th in abundance in relation to other elements in the earth’s

crust and high concentrations are found in granite and in many minerals

including copper, lead, zinc, silver and gold. Arsenic naturally accumulates as

both organic and inorganic forms in soil, surface and groundwater (Smith et al.

1998).

The source and method of arsenic entering the groundwater in Bangladesh is a

controversial issue and has yet to be determined. But it is now widely believed

that the high arsenic levels in the groundwater in Bangladesh have a natural

geological source which may be due to abstraction water from quaternary

confined and semi-confined alluvial or deltaic aquifers. A large number of

diverse chemical and biological reactions, i.e. oxidation, reduction, adsorption,

precipitation, methylation and volatilization participate actively in the cycling of

this toxic element in the groundwater. The main process of arsenic

contamination is explained in two main processes, namely oxidation of arsenic

pyrites or ferrous hydroxides and oxy-hydroxide reduction.

Arsenic pyrites or ferrous hydroxides are very arsenic rich minerals which are

generally stable in reducing environment under the water table and normally

concentrated in organic deposits. But for different anthropogenic activities, like

lowering of water table below the organic deposits, accelerate the oxidation

process. When they oxidized and arsenic is released from the minerals. Some

of them are absorbed onto iron hydroxide. But when water table is recharged

and the arsenic adsorbed onto iron hydroxide returns to the reduced

environment under the water table and mixes with water and caused the

poisoning of water. According to this hypothesis, the origin of arsenic rich

groundwater is man-made, which is a recent phenomenon. Moreover, the whole

processes also accelerate by different geological process like weathering,

erosion, sedimentation, use of irrigation and fertilizers.

According to Oxy-hydroxide Reduction hypothesis, the origin of arsenic rich

groundwater is due to a natural process, and it seems that the arsenic in

groundwater has been present for thousands of years without being flushed from

the delta. Arsenic is assumed to be present in alluvial sediments with high

concentrations in sand grains as a coating of iron hydroxide.  The sediments

were deposited in valleys eroded in the delta when the stream base level was

lowered due to the drop in sea level during the last glacial advance. The organic

matter deposited with the sediments reduces the arsenic bearing iron hydroxide

and releases arsenic into groundwater. Organic matter deposited in the

sediments reduce the arsenic adsorbed on the oxyhydroxides and releases

arsenic into the groundwater and dissolution occurs during recharge, caused by

microbial oxidation of the organic matter as bacteria dissolves surrounding

oxygen.

 H2AsO4 - + 3H+ + 2e- ====> H3AsO3 + H2O

2 H3AsO3 + O2====> HAsO4- + H2AsO4- + 3 H+ (Islam et al. 2007)

1.6 Toxic Effects of Arsenic to Human Health

Arsenic is toxic substance to human health and toxicity depends on the amount

of arsenic intake, which is classified into acute, sub-acute and chronic toxicity

respectively. It is a silent killer. It is 4 times as poisonous as mercury and its

lethal dose (LD) for human is 125 milligram. Drinking water contamination

causes the last variety of toxicity. Undetectable in its early stages, arsenic

poisoning takes between 8 and 14 years to impact on health, depending on the

amount of arsenic ingested, nutritional status, and immune response of the

individual. Arsenic toxicity is dose dependent, and particularly on the rate of

ingestion of arsenic compounds and their excretion from the body but it also

accumulate into the body and passes slowly out through hair and nail. Most of

the ingested arsenic is excreted from the body through urine, stool, skin, hair,

nail and breath. In excessive intake, some amount of arsenic is accumulated in

tissues and inhibits cellular enzyme activities.

Inhalation, ingestion and skin contact are the primary routes of human exposure

to the arsenic. Chronic arsenic ingestion from drinking water is known to cause

skin cancer, and there is substantial evidence that it increases risk for cancers of

the bladder, lung, kidney, liver, colon, and prostate. Recent studies have also

shown that arsenic is associated with a number of non-neoplastic diseases,

including cardiac disease, cerebrovascular disease, pulmonary disease, diabetes

mellitus and diseases of the arteries, arterioles, and capillaries (Engel & Smith

2004). Individuals with chronic Hepatitis B infection, protein deficiency or

malnutrition may be more sensitive to the effects of arsenic (World Health

Organization WHO (1999). Children and older adults may be other groups at

special risk. The Table 1 shows problems and organ of the human body which is

generally affected by arsenicosis. Observable symptom to the arsenic poisoning

can be thickening and discoloration of skin, stomach pain, nausea, vomiting,

diarrhea, numbness in hand and feet, partial paralysis, blindness.

 Table 2: Arsenic infection

Organ System ProblemsSkin Symmetric hyperkeratosis of palms and soles, melanosis or

depigmentation, bowen's disease, basal cell carcinoma and squamous cell carcinoma.

Liver Enlargement, Jaundice, cirrhosis, non-cirrhotic portal hypertensionNervous System Peripheral neuropathy, hearing lossCardiovascular System

Acrocyanosis and Raynaud's Phenomenon

Hemopoietic System

Megalobastosis

Respiratory System

Lung Cancer

Endocrine System Diabetes mellitus and goiter1.7 Arsenicosis effects on cell death signaling

Arsenic induces significant amount of DNA damage. For proper maintenance of

physiological functions, these cells carrying defective genetic information have

to be eliminated from the body, which generally occurs via the programmed cell

death or apoptosis. Significant increase in cytochrome-P450 and lipid

peroxidation accompanied with a significant alteration in the activity of many of

the antioxidants was observed, all suggestive of arsenic induced oxidative

stress. Histopathological examination under light and transmission electron

microscope suggested a combination of ongoing necrosis and apoptosis.

Agarose gel electrophoresis of

DNA of hepatocytes resulted in a characteristic ladder pattern. Chronic arsenic

administration induces a specific pattern of apoptosis called post-mitotic

apoptosis. (Somia et. Al, 2006).

Apoptotic cell death generally occurs through transduction of death signals that

cause morphological changes and affect a number of intracellular key effector

molecules stepwise during the whole process. The cell death signal transduction

triggered by arsenic results in aggregation of the membrane rafts together with

glycosyl phosphotidyl insitol (GPI) anchored cell surface proteins and Thy-1

receptors (in T lymphocytes), reduction of mitochondrial membrane potential,

glutathione production and Bcl-2 expression; elevation of supper oxide

production and Bax protein expression; activation of protein tyrosine kinase

(PTK), mitogen activated protein kinase (MAPK) family kinases, caspases and

Akt; inhibition of NF-кB activity and finally fragmentation of the nuclear DNA

(Scholz et. Al, 2005).

1.8 Blood Serum Parameters

Glucose level and other enzymes like lactate dehydrogenase, alkaline phosphatase, serum glutamic pyruvic transaminase etc. present in blood give important information about how the liver functioning and whether a substance affecting it.

1.8.1 Blood Glucose levels

Glucose, a type of sugar used by the body for energy. The body maintains the

blood glucose level at a reference range between about 3.6 and 5.8 mM

(mmol/L, i.e., millimoles/liter), or 64.8 and 104.4 mg/dL (http://www.faqs.org)

The human body naturally tightly regulates blood glucose levels as a part of

metabolic homeostasis. Glucose is transported from the intestines or liver to

body cells via the bloodstream, and is made available for cell absorption via the

hormone insulin, produced by the body primarily in the pancreas.

The mean normal blood glucose level in humans is about 4 mM (4 mmol/L or

72 mg/dL). However, this level fluctuates throughout the day. Blood sugar

levels outside the normal range may be an indicator of a medical condition. A

persistently high level is referred to as hyperglycemia; low levels are referred to

as hypoglycemia. Diabetes mellitus is characterized by persistent

hyperglycemia from any of several causes, and is the most prominent disease

related to failure of blood sugar regulation. In diabetes mellitus, hyperglycemia

is usually caused by low insulin levels (Diabetes mellitus type 1) and/or by

resistance to insulin at the cellular level (Diabetes mellitus type 2), depending

on the type and state of the disease. Low insulin levels and/or insulin resistance

prevent the body from converting glucose into glycogen (a starch-like source of

energy stored mostly in the liver), which in turn makes it difficult or impossible

to remove excess glucose from the blood.

1.8.2 Lactate Dehydrogenase (LDH)

Lactate dehydrogenase (also called lactic acid dehydrogenase, or LDH) is an

enzyme found in almost all body tissues. It plays an important role in cellular

respiration, the process by which glucose (sugar) from food is converted into

usable energy for our cells.

Although LDH is abundant in tissue cells, blood levels of the enzyme are

normally low. However, when tissues are damaged by injury or disease, they

release more LDH into the bloodstream. Conditions that can cause increased

LDH in the blood include liver disease, heart attack, anemia, muscle trauma,

bone fractures, cancers, and infections such as meningitis, encephalitis, and

HIV.

1.8.3 Alkaline Phosphatase (ALP)

This enzyme works best at an alkaline pH (a pH of 10) and thus the enzyme

itself is inactive in the blood. Alkaline phosphatase acts by splitting off

phosphorus (an acidic mineral) creating an alkaline pH. This enzyme is found in

several body tissues, including the liver. Kids and teens normally have higher

levels of ALP than adults because of bone growth. But ALP levels that are

higher than normal can be a sign of liver diseases or blocked bile ducts.

The primary importance of measuring alkaline phosphatase is to check the

possibility of bone disease or liver disease. Since the mucosal cells that line the

bile system of the liver are the source of alkaline phosphatase, the free flow of

bile through the liver and down into the biliary tract and gallbladder are

responsible for maintaining the proper level of this enzyme in the blood. When

the liver, bile ducts or gallbladder system are not functioning properly or are

blocked, this enzyme is not excreted through the bile and alkaline phosphatase

is released into the blood stream & found in increased concentration.

1.8.4 Serum Glutamic Pyruvic Transaminase (SGPT)

Serum glutamic pyruvic transaminase (SGPT) is one of these enzymes. It's

found in particularly large amounts in the liver and plays an important role in

metabolism, the process that converts food into energy. Normally, ALT is found

inside liver cells. But if the liver is inflamed or injured, ALT is released into the

bloodstream (for example, from viral hepatitis). Measuring blood levels of ALT

can give doctors important information about how well the liver is functioning

and whether a disease, drug, or other problem is affecting it.

Materials and methods

2.1 Sample Collection

Samples for the DNA analysis & measurement of blood serum were collected

from mouse models.

2.1.1 Collection of serum

Blood was collected in eppendorf tubes and kept at room temperature for 10

minutes. After that blood was centrifuged at 3000rpm for 5 minutes at 4C. The

supernatant was taken out using micropipette and collected in fresh eppendorf

tubes. The serum was stored in -78C refrigerator.

2.1.2 Collection of organs for DNA analysis

Part of kidney, liver, and spleen were collected and stored in-78C refrigerator

until samples were prepared for DNA analysis.

2.2 Estimation of blood serum parameters

2.2.1 Determination of serum glucose level

Glucose test is used to determine the amount of glucose in the blood. Serum

glucose concentration was determined using commercially available assay kit

manufactured by Human Diagnostic, Germany according to the manufacturer’s

protocol. In this test glucose oxidase converts glucose in gluconic acid and

peroxidase converts aminoantipyrine into quinoneimine.

β-D- Glucose + O2 + H2O →D-gluconic Acid + H2O2

H2O2 + hydroxybenzoate + 4-aminoantipyrine → Quinoneimine Dye + H2O

Calculation: C= factor x (A sample / A Standard) [mg/dl]

2.2.2 Estimation of serum lactate dehydrogenase (LDH)

Serum LDH level was measured using commercially available assay kit

manufactured by DiaSys Diagnostic Systems, Turkey according to the

manufacturer’s protocol. LDH catalyzes conversion of pyruvate to L-acetate.

Pyruvate + NADH + H+ Lactate + NAD+

Calculation: From absorbance readings A/min was calculated and multiplied

by the corresponding factor.

A/min x factor = LDH activity [U/L]

2.2.3 Estimation of serum alkaline phosphatase (ALP)

Serum Alkaline phosphatase level was measured using commercially available

assay kit manufactured by Biosystems S.A., Spain according to the

manufacturer’s protocol. ALP catalyzes the transfer of the phosphate group

from 4-nitrophenylophosphate to 2-amino-2-methyl-1-propanol (AMP),

liberating 4-nitrophenol. The catalytic concentration was determined from the

rate of 4-nitropjhenol formations, measured at 405 nm.

Calculation: The ALP catalytic concentration in the sample was calculated

using the following general formula:

A/min x [(Vt x 106) / ( x l x VS)] = ALP activity [U/L]

2.2.4 Determination of serum glutamic pyruvic transaminase (SGPT)

Serum SGPT level was measured using commercially available assay kit

manufactured by Human Diagnostic, Germany according to the manufacturer’s

protocol. It catalyzes the transfer of an amino group from alanine to α-

ketoglutarate, the products of this reversible tarnsamination being pyruvate and

glutamate. The catalytic concentration was measured at 340 nm.

Glutamate + pyruvate α-ketoglutarate + alanine

Calculation: From absorbance readings A/min was calculated.

A/min x factor = SGPT activity [U/L]

2.3 Analysis of genomic DNA

2.3.1 Sample preparation for DNA analysis

100µl of liver cell suspension was added with hypotonic lysis buffer (50mM

Tris-HCl, 10mM EDTA, 0.5% SDS) followed by centrifugation at 13000 rpm

for 5 minutes at 4°C. Extraction with phenol:chloroform:isoamylalcohol

(25:24:1) was done twice.

Ethanol washed DNA pellet was dissolved in 100 l TE buffer. Resultant

solution was incubated at 55°C for 1 hour.

2.3.2 Agarose gel elctrophoresis

5.0 µl of DNA sample mixed with 2.0 µl dye and was loaded on 1.0% agarose

gel (with 0.1 µg/ml ethidium bromide). The sample was run for about 1.0 hour

at 80 mV. Gel was observed under UV light for viewing DNA bands.

Photographs of gel were taken.

Results

3.1 Effect of arsenic on various Serum parameters

Blood serum was collected as described in material and method section

followed by analysis. Than it was examined whether arsenic could affect

various physiological parameters of blood serum.

3.1.1 Arsenic induced elevation of serum glucose level

Serum glucose level was found elevated in arsenic exposed mice (178.2gm/dl)

than normal levels (110 gm/dl) which indicating possibilities of diabetes

induction mediated by arsenic (Figure 3)

Figure 3: Arsenic induced elevation of serum glucose

3.1.2 Arsenic induced elevation of serum enzymes (LDH, ALP and SGPT)

Next, various enzyme parameters were determined. The level of LDH in control

was found 686.5 U/L, which was increased to 1156.5 U/L by arsenic exposure

(Figure 4). This increase indicated possibilities of heart tissue damage in

arsenic-exposed mice. Heart tissue damage might cause release of heart LDH

into the bloodstream.

Arsenic-exposed mice also showed an increase in serum ALP concentration

(425 U/L) compared to control (305.5 U/L) (Figure 4). In conditions affecting

the liver, liver cells might release higher amounts of alkaline phosphatase (ALP)

into the blood.

Serum SGPT is commonly measured clinically as a part of a liver function test.

Arsenic-exposed mice significantly increased SGPT level in serum (135.2 U/L)

whereas control mice had 92.14 U/L. This indicated a possibility to liver

damage caused by arsenic (Figure 4).

Figure 4: Arsenic induced elevation of serum enzymes

3.2 Examination of arsenic mediated DNA damage

From earlier researches it was found that arsenic induces apoptosis in vitro

involving fragmentation of chromosomal DNA (Hossain et. al, 2000). As

arsenic was found to be heavily deposited in liver, it was next examined where

this deposited arsenic could affect the chromosomal DNA of the liver cells in

vivo. Chromosomal DNA from the liver tissue was isolated from all of four

groups as described in methods and materials. The isolated DNA was resolved

by agarose gel electrophoresis. Genomic DNA was detected at the upper portion

of the gel. No clear band for fragmented DNA was observed in arsenic exposed

liver cell, although little smear of DNA was viewed (data not shown because the

quality of the photo graph was not up to the mark). This result suggested that

DNA was probably not damaged by arsenic exposure in vivo.

Discussion

Arsenic toxicity has become a global concern owing to the ever-increasing

contamination of water, soil, and crops in many regions of the world especially

Bangladesh. If an individual exposed to arsenic, it accumulates in tissues and

blood causing various devastating diseases such as skin leisons, kerotosis,

cancers of the skin, lung, bladder and liver (Chen et al., 1992), blackfoot

disease (Tseng, 1989), diabetes mellitus (Lia et al., 1994), hypertension

(Chen et al., 1995), atherosclerosis (Simeonova et. al, 2004) etc.

Arsenic caused elevation of glucose level (Figure 3). It was reported earlier that

exposure to arsenic in drinking water resulted in proportional increases of its

metabolites in the liver and in organs targeted by type 2 diabetes, including

pancreas, skeletal muscle and adipose tissue (David et al. 2007).

Lactate dehydrogenase (LDH) catalyzes the conversion of lactate to pyruvate.

This is an important step in energy production in cells. Many different types of

cells in the body contain this enzyme. Some of the organs relatively rich in

LDH are the heart, kidney, liver, and muscle. After the death of cells their LDH

is released into the bloodstream. Arsenic is reported to have association with

ischemic heart disease, acute myocardial infarction, atherosclerosis, and

hypertension (Navas et al. 2005, Xia et al. 2009). In this study, the LDH level

was found very high in arsenic-exposed mice (Figure 4). This indicated

possibilities of heart tissue damage in arsenic-exposed mice. Heart tissue

damage might cause release of heart LDH into the bloodstream. Arsenic showed

increased risks for acute myocardial infarction (Yuan et al. 2007).

Elevation of serum ALP and SGPT level was also observed (Figure 4). All these

enzymes are considered as important liver enzymes. Elevation of these enzymes

clearly indicated that arsenic caused liver damage.

Arsenic has been previously reported to induce apoptotic death of cells

‘in vitro’ through involving DNA fragmentation (Hossian et. al, 2000). DNA

from the liver tissue was isolated from all of four groups of mice and resolved

by agarose gel electrophoresis. Genomic DNA was detected at the upper portion

of the gel. No clear band for fragmented DNA was observed in arsenic exposed

liver cell, although little smear of DNA was viewed. This result suggested that

DNA was probably not damaged by arsenic exposure in vivo. Usually in ‘in

vivo’ system, apoptosis involving DNA fragmentation is sometimes difficult to

be attained. This is probably because in ‘in vivo’ system, various biochemical

and immunological recovery activities might work together to prevent arsenic-

mediated damage of DNA.

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