The object of the present study is to measure the concentrations of toxic heavy metals in human eyes (cadimium and chromium) and major mineral iron ion. The heavy metals cadimium, chromium and iron were assayed using atomic absorption spectrometry. Metals determination in human eye is the most common application of biological monitoring for screening diagnosis and assessment of metals exposures and their risks. The statistical analysis of the metals (cadimium, chromium and iron) levels in human eyes showed that levels of the three metals in non-smoker were lower than metals contents of the smoker groups. Metals levels in human eyes of males were significantly lower than females. Statistically significant differences (p < 0.001) were observed between persons living in city centre and others who living in outskirt for concentrations of all three metals. Geographical influences are thought to be the main source of variability.
Heavy Metals; Human Eyes; Atomic Absorption1. Introduction
Human cells employ metals such as zinc, copper and iron to control significant metabolism and signling functions making them essential for life [1]. Many heavy metals play an important biological role, the particular importance of iron and copper ions in biological processes [2]. Redox-active metals such as iron, copper and chromium undergo redox recycling to produce free radicals. In contrast cadimium and mercury are redox-inactive metals that challenge antioxidant defenses by binding to thiols in cell [3,4]. The natural aquatic systems may extensively be contaminated with heavy metals released from domestic industrial and other man made activities [5]. The toxic effect of heavy metals usually involves an interaction between the heavy metal ion and specific target protein resulting in a change in protein structure and function [6]. Chromium in its hexavalent form which is the most toxic species of chromium is used extensively in some industries such as leather processing. The toxicity of chromium stems from its tendency to be corrosive and to cause allergic reactions. Chromium is a carcinogen, particularly of the lung through inhalation. Cell toxicity caused by heavy metal ions is attributed to oxidative and nitro sativa stress [7], defined as an oxidants over antioxidants. Macro molecules in cell are damaged by metals-induced production oxygen and nitrogen-containing free radicals (oxidants) and/or metal induced depletion of the cells antioxidant defense programmed cell death or necrotic cell death are usual consequences [8]. Oxidative stress has been recognized as underlying mechanism in toxicity associated with numerous metals. Metals either undergo redox cycling (Fe, Cr and Cu) or deplete cells antioxidant pool (Cd, Pb and Ni) and induce oxidative stress [9].
This paper deals with the quantitative determination of cadimium, chromium and iron concentration of human eyes subjects exposed to these metals along with their respective controls. The purpose of this research is to quantify the accumulation of heavy metals (cadimium, chromium and iron) in human eye lenses.
2. Materials and Methods2.1. Apparatus
Ashimadzu atomic absorption spectrophotometer model (AA-630-12) was used with an air-acetylene burner (slot dimensions 100 × 0.62 mm). Instrument settings were: lamp current, 10 mA; wave length, 285.2 nm; slit width, 0.2 nm. These conditions were maintained constant throughout the measurements.
2.2. Reagents
Metals stock solutions: Add 200 mg of magnesium metals to a 100 ml volumetric flask. Dissolve using the minimal quantity of hydrochloric acid. Dilute to volume with deionized water.
Metals working standards: Transfer (0.5 - 5) ml of the stock solution to ten a 100 ml. Volumetric flask and dilute to volume with deionized water. This gives a concentration of (10 - 100) μg Metal/ml.
2.3. Preparation of Samples
Each lens was placed into pre weight digestion tube. The sample was weighted to determine a dry weight (gram) after drying at 95˚C overnight [7]. Next day reweighed to determine dry weight (gm), then (1 ml) of concentrated nitric acid was added digest tube which was placed in waterbath at 100˚C, the sample digested for approximately 1 h. until all tissues material has been dissolved, then (1 ml) perchloric acid was added until (deep brown color) with clear solution was obtain dilute each sample to mark with deionized water to 10 ml.
2.4. Statistical Analysis
The statistical analysis was carried out using two-way analysis of variance with unbalanced repeated measurements. Statistical significance between individual time points was made by using Revised Least Significant Difference (RLSD) test. The probability level for significance was 5% less.
3. Results and Discussion
In our laboratory the measurements of concentrations of metals, cadmium and chromium and iron in human eyes samples Table 1 show their characters. All the measurements of the eyes samples subjected to statistical analysis using the independent samples RLSD-test to compare between measurements of the study groups (smoker and none-smoker), sex (males and females) and life environment (Outskirts and citycentre).
The statistic results showed that there is a significant difference (p < 0.001) in the metal levels in all the compared males and females eyes measurements as shown in Figure 1 the concentration of the three metals in eyes about 10% excess in females higher than in males. From these findings, it would appear that while variation does occur in concentrations of metals in eyes with difference in sex, no definite pattern of distribution is present.
Figure 2 illustrates the variation in the concentration of metals in human eyes as a function of life environments. Statistically significant differences (p < 0.001) were observed between persons living in city centre and others who living in outskirt for concentrations of all three metals. Geographical influences are thought to be the main source of variability. The observed variations are probably a reflection of the varying levels present in foods that are generally dependent on geochemical environment in which they are living. Environmental contamination can also be a source of metals a human eyes.
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