Examination of Cardiovascular Toxicity and Trace Elements Status in Albino Rats Treated with Okposi and Uburu Salt Lakes (Nigeria)
This study was aimed at investigating the effect of water and salt samples from Okposi and Uburu salt lakes on some serum trace elements and the cardiovascular system. Serum levels of copper (Cu), cadmium (Cd), cobalt (Co) manganese (Mn), cardiac troponin I (cTnI) and lipid profile were measured in albino rats after treating them with different doses of salt and water from the lakes for seven consecutive days. Average body weight, physical activities and food and intake decreased in all the treated groups compared with the control. The levels of Cu, Cd, Co and Mn in test groups were significantly higher (p<0.05) than in the control. There was a significant increase (p<0.05) in the concentrations of cardiac troponin I, cholesterol, triacylglycerol and low density lipoproteins, in the treated groups relative to the control while high density lipoproteins in the control were significantly higher (p<0.05) than the treated groups. The observations were also statistically more pronounced (p<0.05) in the groups given water samples than those administered salt samples. The differences in the levels of these parameters between groups given Okposi samples and those treated with Uburu samples were not significant (p>0.05). The effects of the samples were found to be dose- dependent. These results indicate that the samples may be toxic to the cardiovascular system and this toxicity may be reduced by the methods of processing the salt. The toxicity of the samples may be due to the chemical contents of the lakes.
February 21, 2011; Accepted: June 24, 2011;
Published: July 16, 2011
Lakes are products of volcanic, glacial, tectonic and river activities which
leave depressions and cavities on land surface (Charles et
al., 1999). A salt lake is a land locked body of water which has a concentration
of salts (mostly sodium chloride) and other minerals significantly higher than
most lakes (often defined as 3 g salt per litre). Salt lakes have been shown
to contain metallic and non metallic ions such as calcium, cadmium, lead, mercury,
manganese, bicarbonate, Sulphate, bromine, fluorine, etc in addition to sodium
and chlorine (Agbafor et al., 2010). Indeed,
a salt lake is a complex solution of mineral salts and decayed biological matter
that results from life in the lake. The chemical constituents of salt lakes
originated from either natural processes (erosions and weathering of coastal
materials) or anthropogenic sources (domestic, industrial and agricultural practices)
(Charles et al., 1999).
Okposi and Uburu salt lakes are located in Ohaozara local government area of Ebonyi state, Nigeria. The lakes serve as salt (obtained after heating lake water to dryness) and water sources for most domestic purposes of the inhabitants of the communities who are mainly farmers.
Akubugwo et al. (2007) have reported the presence
of metallic and non-metallic ions in the lakes. Hepatotoxicity of the salt lakes
has been demonstrated by Akubugwo and Agbafor (2007).
Copper (Cu) toxicity may lead to liver impairment, gastrointestinal tract disturbance,
loss of appetite, anemia, nervous system damage, renal failure, cardiovascular
collapse, tachycardia and so on (Sarava et al., 2007).
Exposure to cobalt results to a wide spectrum of toxicities in mammals. Cobalt
toxicity results to polycythemia, hypertriglyceridemia, hypercholesterolemia,
cardiomyopathy, etc. (Taylor and Marks, 1978). The adverse
health effects caused by ingestion or inhalation of cadmium (Cd) include renal
tubular dysfunction from high urinary excretion of Cd, lung damage, lung cancer
and hypotension (Yu, 2001). Exposure to manganese (Mn)
may lead to neurological disorders similar to those of Parkinsons disease.
Manganese interferes with absorption of dietary iron, resulting to iron deficiency.
It also impairs the activity of Cu metalloenzymes (Blaurock,
The cardiovascular system refers to the heart and the blood vessels. The heart
is a muscular organ responsible for moving blood through the vessels to all
parts of the body (Burtis and Ashwood, 2003). Cardiac
troponins I are cardiac markers with extraordinary high specificity for myocardial
cell injury. They can be used in a variety of clinical situations, including
differentiation of skeletal from cardiac muscle injury; detection of minor myocardial
cell damage, detection of preoperative myocardial infarction and estimation
of infarct size (Coudry, 1998). Acute myocardial injury
can be sensitively and accurately identified by measurement of plasma or serum
concentration of cardiac troponin I (cTnI), one of the contractile proteins
of the myocardium. A rise in the concentration of TnI in the circulation indicates
various degrees of myocardial cell damage (Cardinale et
al., 2002). Lipid profile constitutes total cholesterol, High Density
Lipoproteins (HDL), Low Density Lipoproteins (LDL), Very Low Density Lipoproteins
(VLDL) and triacylglycerols. Examination of lipid profile is useful in assessment
of the risk of cardiovascular disease (Robert, 2006).
Okposi and Uburu salt lakes have been reported to be toxic to hepatic and renal
systems. In this communication, the present study investigated the effect of
the lakes on the cardiovascular system.
MATERIALS AND METHODS
Collection of samples: Each of the lakes was divided into transects of North, South, East and West from a reference epicenter. The study was performed in the month of March, 2010. Five water samples were randomly collected from each of the transects and pooled to get a unity sample. In the same vein, five salt samples of each lake were obtained from the local people and pooled in each case to also get a homogenous unity sample. The 0.1 g mL-1 salt solution was prepared with deionized water.
Animals and handling: Forty-five adult male albino rats, weighing 110-122 g were brought from the animal house of Biochemistry Department, University of Nigeria, Nsukka. They were placed in nine groups (A-I) of five rats in each group and kept in animals house of Biochemistry Department, Ebonyi State university Abakaliki for seven days to acclimatize. All the rats were allowed free access to feed (rat chaw) and water before and throughout the experiment.
Animal groups and treatments:
|Group A :
||50 mg kg-1 body weight salt solution from Okposi
|Group B :
||100 mg kg-1 body weight salt solution from Okposi lake
|Group C :
||1 mL kg-1 body weight salt water from Okposi lake
|Group D :
||2 mL kg-1 body weight salt water from Okposi lake
|Group E :
||50 mg kg-1 body weight salt solution from Uburu lake
|Group F :
||100 mg kg-1 body weight salt solution from Uburu lake
|Group G :
||1 mL kg-1 body weight water from Uburu lake
|Group H :
||2 mL kg-1 body weight water from Uburu lake
|Group I :
||Deionized water (used to dissolve the salts)
The treatment was done orally for seven consecutive days.
Collection of blood for analysis: Blood samples were collected from the animals following an overnight fast through cardiac puncture under mild anaesthesia using diethylether. The samples were put into specimen bottles without anticoagulant.
Analysis of trace elements: Serum levels of Cu, Cd, Co and Mn were measured
with flame Atomic Absorption Spectrophotometer (AAS) using a direct method described
by Kaneko (1999).
Measurement of serum cardiac troponin I levels lipid profile: The method
employed for cardiac troponin I (cTnI) determination was an immunoenzymatic
fluorescent assay of Bodor et al. (1992). The
serum concentrations of the individual component of lipid profile were determined
according to the methods used by Akpanabiatu et al.
Data analysis: Statistical analysis was done using Analysis Of Variance
(ANOVA). Means were compared for significance using Duncans Multiple Range
test (p<0.05) (Sokal and Rholf, 1969).
RESULTS AND DISCUSSION
There were significant decreases in physical activities, food and water intake
in the treated groups (data not shown) while the control group thrived. These
observations may be attributed to the chemical constituents of the salt lakes
(Yu, 2001). The presence of Pb, Mn, Cr, Cu, Fe, Cd etc,
in concentrations higher than WHOS permissible limit have been reported
in water sources, including the lakes and biological fluids of residents of
Okposi and Uburu communities (Akubugwo et al., 2007;
Akubugwo and Agbafor, 1997). The manifestations of Pb
poisoning among other disorders include muscle aches, pains and loss of appetite
(Yu, 2001). These may have contributed to the observed
decrease in physical activities, food and water intake. Further, distortion
of metabolism by other constituents of the lakes may not be ruled out. Some
surface water in Nigeria are known to be polluted such that their constituents
elicit adverse effects (Agbafor et al., 2010).
The result of changes in body weight of the animals during the period of treatment
is shown in Table 1. There was a significant decrease (p<0.05)
in weight of the test groups compared with the control (which gained weight).
This may be attributed to the reported reduction in food and water intake. However,
direct effect of the constituents of the lakes water in the rats which will
cause metabolic changes consequent upon their ingestion certainly contributed
to observed changes. For example, symptoms of cadmium (Cd) toxicity include
sensory disturbances and weight loss (Yu, 2001). These
observations are inline with those reported by Akubugwo
and Agbafor (2007).
Table 1 also presents the effect of the samples on trace
elements ( Cu, Cd, Co and Mn) of the animals after administration. There was
a significant increase (p<0.05) in the levels of the trace elements in treated
groups relative to the control.
|| Change in body weight and serum levels of Cu, Cd, Co and
Mn of the rats after seven days of treatment
|Values are Mean±SD. Values bearing different superscripts
differ significantly (p<0.05). n = 5. Table 1 shows
changes in weight and trace element levels of the rats during and after
treatment respectively. Weight changes ranged from 4.95±1.11 to 17.88±1.60
g while in trace elements, Cu produced highest value of 226.23±5.14
μg dL-1 and Co least with a value of 0.17±0.02 μg
The increase in the levels of these trace elements may be related to their
reported high levels in the salt lakes (Akubugwo et al.,
2007; Akubugwo and Agbafor, 1997).
The effects of the water and salt samples on serum levels of cardiac troponin
I and lipid profile are presented in Table 2. The concentrations
of cardiac troponinI in the treated groups were significantly higher (p<0.05)
than in the control group. Although the biochemical basis of this increase is
currently obscure, it may be attributed to damage of heart muscle cells (myocytes).
Measurement of plasma or serum concentration of cardiac troponin I, one of the
contractile proteins of the myocardium, can be used to sensitively and accurately
identify acute myocardial injury. Elevation of circulatory level of this protein
indicates various degrees of myocardial cell damage (Cardinale
et al., 2002). The chemical constituents of the lakes may be responsible
for this possible myocardial cell injury. For example, animal studies indicate
that manganese is capable of quickly accumulating in the heart tissue, resulting
in acute or subacute cardiovascular disorders, such as acute cardiodepression
and hypotension. These toxic outcomes appear to be associated with Mn-induced
mitochondrial damage and interactions with the calcium channel in the cardiovascular
system (Jiang and Zheng, 2005). Copper toxicity has
been linked with cardiovascular collapse, hypotension and tachycardia. Severe
methemoglobinemia, caused by Cu, can result in cardiac dysryhtmia and hypoxia
which could contribute significantly to cardiovascular collapse. Other factors
are direct effect of Cu on vascular and cardiac cells and sepsis due to transmucosal
invasion (Sarava et al., 2007). Further, according
to Liu et al. (2010), microscopic observation
showed that high-dose cobalt chloride caused significant hyperemia, swelling
of the heart and spotty necrosis. Cobalt ions are present in the body as radical
ions which can caused lipid peroxidation, leading to decreased fluidity, increased
fragility and altered permeability of cell membranes (Liu
et al., 2010).
The results of lipid profile shown in Table 2 indicates the
levels of cholesterol, triacylglycerols and low density lipoproteins in the
test groups increased significantly (p<0.05) relative to the control while
high density lipoprotein in the control was significantly higher (p<0.05)
than in the treated groups. The actual mechanism involved in these observations
is currently being studied. However, the effects of the constituents of the
samples administered to the animals may have contributed. For instance, one
effect of cobalt administration on blood is an increase in triacylglyerols,
cholesterol and free fatty acids (Taylor and Marks, 1978).
|| Serum cardiac troponin I levels and lipid profile of the
rats after seven days of treatment
|Values are Mean±SD. Values bearing different superscripts
differ significantly (p<0.05). n = 5. In Table 2, serum
cTnI ranged from 0.42±0.02 to 3.50±0.12 mg mL-1.
TC, TG, HDL and LDL were 134.33±2.66 to 428.77±3.50, 98.15±3.50
to 402.17±3.23, 4.65±0.63 to 39.51±2.10, 46.36±3.44
to 343.69±2.62, respectively, LDL: Low density lipoprotein, TC: Total
cholesterol, cTnI: Cardiac troponin I, TG: Triacylglycerol, HDL: High density
This may be due to inhibition of tissue lipoprotein lipase, resulting in the
failure to clear very low lipoproteins (Taylor and Marks,
1978) and perhaps by stimulation of lipoprotein synthesis by the liver (Eaton,
The chief role of cholesterol, triacylglycerols and lipoproteins (except high
density lipoproteins) in pathological processes is as factors in the genesis
of atherosclerosis of vital arteries, causing cerebrovascular, coronary and
peripheral vascular disease (Murry et al., 2003).
For example, low density lipoproteins pose a risk for cardiovascular disease
when it invades the endothelium and becomes oxidized, since the oxidized form
is more easily retained by proteoglycans (Cromwell and Otvos,
2004). This oxidation is chiefly stimulated by free radicals in the endothelium
(Cromwell and Otvos, 2004).
Comparing the groups treated with salt solution with those given lake water,
the later consistently showed higher potency. This points to the fact that the
procedures involved in the processing of the salt water into salt affect the
chemical composition of the salt lakes. The difference between the results from
the groups treated with samples from Okposi and those from Uburu was not significant
(p>0.05). The effects of all the treatments were found to be dose-dependent.
These observations have been reported by Akubugwo and Agbafor
Water and salt from Okposi and Uburu salt lakes are toxic. Their toxicity may be due to their constituents which include high levels of trace elements. The methods of salt production used by the indigenes contributed to reduction of this toxicity. The results of this study suggest that continuous consumption of water or salt samples from the lakes may elicit various disorders, including loss of appetite and cardiovascular system disorders. However, proper methods of processing are required to reduce the toxicity of the lakes water.
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