Accumulation of heavy metals in the tissues of aquatic animals can become toxic when accumulation reaches a significantly high level (Joseph et al., 2012). Heavy metals enter the fish's body from contaminated water via different routes and accumulate in different organs of fish (Olaifa et al., 2004). Various organs of fish absorb heavy metals due to the affinity between them and concentrated at different levels in different organs of the body (Scharenberg et al., 1994).
The tropes related to accumulation of heavy metals in freshwater fish and enzymatic variations in different organ of fish have been carried out in a number of journals. 2014) studied heavy metal toxicity and bioaccumulation patterns in the body organs of four freshwater fish species. The heavy metals can enter the fish's body via different routes from contaminated water and accumulate in organisms.
2014) conducted a study on heavy metal toxicity and bioaccumulation patterns in the body organs of four freshwater fish species. Cirrhinus cirrhosus contains heavy metals in the order liver > kidney > gills > intestine > skin > scales > bones > muscles > fins;
Role of heavy metals as a bio-indicator
Environmental aspects of heavy metal
Detrimental effects of arsenic, lead and chromium on human
ATPase is probably the most important enzyme in the plasma membrane of an animal cell, but the role of the membrane in its regulation is poorly understood. This action has been estimated to account for approximately 25% of the standard metabolic rate, making the pump one of the most energetically important proteins in the cell. In the osmoregulatory epithelium of vertebrates, this role is modulated to meet the demands of ion homeostasis. 2010) studied the possibilities of fish farming in the wide channel and furrow system in Andaman.
2006) conducted an experiment on reduced gill ATPase activity in freshwater fish Channa punctata (Bloch) exposed to diluted effluent from a paper mill. 2017) conducted an experiment on the biochemical effects of salinity on catfish, Heteropneustes fossilis (Bloch, 1794), and the possibility of their cultivation in low-salinity water. A decrease in hepatic ALP activity may occur due to sudden changes in metabolism to supply additional energy in the hyperosmotic state. 2007) conducted an experiment on enzymatic responses to metal exposure in the freshwater fish Oreochromis niloticus.
Na,K-ATPase activity in the gills and intestine was inhibited by all metal exposures. Structural level changes in marker proteins and enzymes have been found due to lead toxicity.
MATERIALS AND METHODS
- Study area
- Sample collection process
- Dissection of fish sample
- Heavy metal analysis
- Sample preparation for enzyme analysis
Each of the collected fish samples was dissected and its gill, muscle, liver and kidney tissues were collected. The collected gill, muscle, liver and kidney tissues were stored in a plastic jar as a sample. All methods of sample preparation and analysis were performed according to the procedure described in UNEP Reference Methods (1984). For further analysis, the prepared samples were stored in a 10% formalin solution.
The selected tissues of the sample were digested with concentrated nitric acid and perchloric acid (2:1 v/v) at 60 ºC for 3 days. After acid digestion, all samples were analyzed for three heavy metals (As, Pb, and Cr) by atomic absorption spectrometry (Phillips AAS with double beam and deuterium background corrector). Analytical blanks were run in the same manner as the samples and determined using standard solutions prepared in the same acid matrix.
Each of the dissected parts was mixed separately in chilled sucrose solutions (0.25 M) with a mechanical tissue homogenizer (WN-AD200LPN, China) to prepare 5% homogenate. The homogenate was centrifuged at 3000 g for 15 min using a laboratory centrifuge (centrifuge 5702R, Germany); the supernatant was collected and stored at -20°C for further analysis within 1 to 2 days. The ALP (alkaline phosphates) activity of the liver and kidneys was tested using the standard method reported by Garen (1960). In the muscles, ALP (alkaline phosphate) activity was determined using the standard method reported by Levinthal (1960).
ATPase enzyme activity was determined following the standard method stated by Post and Sen (1967). A mixture of 100 mM NaCl, 3 mM magnesium chloride, 0.1 M HCl buffer, 20 mM potassium chloride, 0.1 mL tissue homogenate, and 5 mM ATP was prepared and used. The reaction mixture was incubated for 15 min and 10% TCA was used to stop the reaction.
All data collected during the experimental period and the laboratory test were recorded and stored on the computer. One-way analysis of variance (ANOVA) and Duncan's multiple range test were used to assess whether metal concentrations differed significantly between species and different organs. The comparative accumulation of Lead (Pb), Arsenic (As) and Chromium (Cr) in each species was demonstrated using Microsoft Excel.
RESULTS
- Different heavy metals concentration in gills of rohu fish
- Different heavy metals concentration in gills of cultured catla fish
- ALP activity in different organs of cultured rohu fish
- ALP activity in different organs of cultured catla fish
- DISCUSSION
- CONCLUSION
The obtained values of various heavy metals in the kidneys of cultivated rohu are statistically significantly different from each other. Among the investigated heavy metals (As, Pb, Cr), the concentration of lead (0.008 ppm) was the highest in the muscles of rohu fish, followed by the concentration of chromium (0.006 ppm) and arsenic (0.004 ppm), although the values are not statistically significant. . 28 | Page Figure 5: Different concentrations of heavy metals in the gills of a farmed cat 4.6 Different concentrations of heavy metals in the liver of a farmed cat.
Among the heavy metals studied (As, Pb, Cr), the concentration of lead (0.006 ppm) was the highest in the muscles of catla, followed by the concentration of chromium (0.003 ppm) and arsenic (0.002 ppm), although the values are not statistically significant ( P < 0.05). 30 | Page Figure 8: Different heavy metal concentrations in muscles of cultured catla 4.9 ATPase activity in different examined organs from cultured rohu fish. 32 | P a g e Figure 11: ALP activity as n mol para-nitrophenol mg protein-1 (37°C) in different organs of cultured rohu fish.
The average mean value of chromium (Cr) was the lowest (0.003 ppm) among the three heavy metals studied, which is much lower than the standard value (0.1 ppm) of chromium (WHO/FAO, 2005). Heavy metals remain in the environment for a long time because they are non-biodegradable substances and can be concentrated all the way up the food chain (Eja et al., 2003). Heavy metals accumulate in living organisms when they are taken up and stored faster than they are broken down (metabolized) or excreted.
They enter the water body through industrial and consumer materials or even through acid rain, which decomposes the soil and releases heavy metals into various water bodies (Pandey et al., 2014). The level of heavy metals in fish varies from species to species and different aquatic habitats. Among the various heavy metal values achieved, we found that Pb concentrations in various tissues of empirical fish species were much higher than all other concentrations of other heavy metals, while Cr showed the lowest values in almost all experimental organs.
The heavy metals such as Arsenic (As), Cadmium (Cd), Lead (Pb), Chromium (Cr) and Mercury (Hg) are most poisonous to all animals, fish, humans and also the environment. Although some heavy metals are essential for animals and several other organisms, all heavy metals exert their toxic effects through metabolic interference and mutagenesis. With increasing heavy metals in the aquatic environment, these elements bioaccumulate in the food chain, leading to toxicity in animals, including fish.
Kidneys and liver are the most sensitive organ of fish to accumulate the toxic heavy metals. To reduce the level of heavy metal concentration in fish and other organisms, close monitoring of the aquatic environment is a must.
RECOMMENDATION AND FUTURE PERSPECTIVES
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