Metal Accumulation and Antioxidant Enzyme Activity in C. gariepinus, Catfish, and 0. mossambicus, Tilapia, Collected from Lower Mguza and Wright Dams, Zimbabwe
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Date
2009-08-28
Journal Title
Journal ISSN
Volume Title
Publisher
Springer Science+Business Media
Abstract
The aim of this study was to measure antioxidant
enzyme activities as biological indicators of pollution in
tissues of two species of fish. Five Clarius gariepinus and
three Oreochromis mossambicus were collected from Umguza
Dam (polluted dam) whilst seven C. gariepinus and
eight 0. mossambicus were collected from Wright Dam
(relatively pristine dam). Diphosphotriphoshodiaphorase
and catalase activities were consistently lower (42 f 2%
and 78 f 20%, respectively) in liver whilst malondialdehyde
levels were two times higher in muscles of both species
of fish collected from Umguza Dam. However, seleniumdependent
glutathione peroxidase (Se-GPX) activity was
elevated four-fold in liver and gills of 0. mossambicus collected
from Umguza Dam. Metal levels were two to five
times higher in muscles of both species of fish collected from
Umguza Dam. Fish from Umguza Dam seem to have
responded to pollution by increasing Se-GPX specific
activity in an effort to detoxify peroxides produced as a result
of metal induced oxidative stress.
Keywords Antioxidant enzymes . Heavy metals .
0. mossambicus . C. gariepinus
High levels of trace metals in freshwater may occur as a
result of natural weathering of minerals in the sediments
and bed rocks or as a result of anthropogenic activities such
as mining, industrial, municipal and agricultural discharges
(Winston 1991). Most trace metals are essential in small
concentrations for normal metabolic processes in mammals
including fish and humans. At abnormally high concentrations,
metals can cause death in fish. Metals such as lead
(Pb), cadmium (Cd), copper (Cu) mercury (Hg), silver (Hg)
and cobalt (Co) have been shown to be extremely toxic
when they bind to fish gills (Tao et al. 2000). Fish are
exposed to metals through contaminated food and the water
column in chronically contaminated aquatic ecosystems,
the main routes of accumulation being through gills (Tao
et al. 2000). Sublethal and chronic concentration of metals
exerts their toxicity on fish by generating free radicals such
as the hydroxyl radical ('OH), peroxyl-radical (Roo2) and
superoxide (Oo2-) and some non-radical ROS such as
hydrogen peroxide (H202). These ROS can trigger oxidative
damage to proteins, nucleic acids and lipids (Winston
1991). However, defensive antioxidant enzymes, which
detoxify reactive oxygen species, are present in the liver,
kidneys, gills and intestine (Buhler and Williams 1988).
Antioxidant enzymes have been used as biomarkers of
pollution by metals and organic compounds that generate
oxidative stress in molluscs (Cossu et al. 2000) whilst MDA
levels have also been shown to be affected by oxidative stress
(Rodrigues-Ariza et al. 1993). As antioxidant enzyme
activities and MDA levels can be used as biomarkers of
pollution, this study was undertaken to determine the relat~
onship between concentration of metals, antioxidant
enzyme activities and MDA levels in two species of fish
collected from Mguza Dam (which receives domestic and
industrial effluent from Bulawayo City sewage works) and
from Wright Dam with no history of pollution.
Description
Bull Environ Contam Toxicol Article
Keywords
Antioxidant enzymes, Heavy metals, 0. mossambicus, C. gariepinus
Citation
Siwela, A. H., Nyathi, C.B., Naik, Y.S (2009) Metal Accumulation and Antioxidant Enzyme Activitity in C. gariepinus, Catfish, and 0. mossambicus, Tilapia, Collected from Lower Mguza and Wright Dams, Zimbabwe.,Springer Science+Business Media