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al. (2002) studied LMS in livers of the flounder ( Platichthys flesus) ) from the North Sea; the
lysosomal membrane was affected in fish from the Elba river between 1995 and 1999 but
then recovered its integrity in 2000. On the other hand, fish from the Eider river or around
Helgoland, which are located farther from pollution sources (DDT and PCB) than the Elba
river, showed a decrease in the integrity of lysosomal membrane that has been constant
between 1995 and 2000. The authors suggest that the fish populations not continuously
exposed to anthropogenic stress have a lower potential or take longer time to recover a
good physiological state.
2.4.4 Thiobarbituric Acid Reactive Substances
Deficiency of antioxidant defense systems to eliminate an excess of ROS could induce dif-
ferent types of cellular damage, of which the most widely studied is the peroxidation of
lipids (Figure 2.2), able to induce structural and chemical alterations of cellular membranes
(Livingstone et al. 1990; Winston and Di Giulio 1991; Vasseur and Cossu-Leguille 2003;
Valavanidis et al. 2006). The process of lipid peroxidation involves a chain of reactions
leading to the breakdown of polyunsaturated fatty acids that are relatively sensitive to oxi-
dative reactions. Their degradation induces the formation of various compounds such as
lipid alcoxyl radicals, ketones, alkanes, epoxides, and aldehydes. Among them, malondial-
dehyde (MDA) is both the most important and the most studied. Most of these compounds
are toxic and mutagenic. The peroxidation of lipids could be initiated by hydroxyl radicals
particularly in reactions catalyzed by transition metals (Viarengo et al. 1990; Valavanidis
et al. 2006; Almeida et al. 2007).
The effects of lipid peroxidation can be assessed at the different steps of the lipid break-
down: at the initial phase (conjugated diene), intermediate phase (lipid hydroperoxides),
or final phase [substances (TBARS) reactive with thiobarbituric acid (TBA) considered as
MDA-like peroxides]. This test based on the use of these substances mainly reveals the
formation of MDA by colorimetric or fluorimetric methods. Because TBA can react with
compounds other than MDA, the results are usually expressed as TBARS concentrations
(Knight et al. 1988; Pannuzio and Storey 1998; Durou et al. 2007).
The levels of MDA and TBARS have been used as markers of oxidative stress indicating
the peroxidation of cellular membranes in numerous marine and freshwater invertebrate
and vertebrate species. They can be influenced by different environmental parameters
such as salinity and temperature in bivalves (Damiens et al. 2004) or in fish and can
increase 20-fold in goldfish ( Carassius auratus ) exposed to a temperature elevation of 14°C
(Lushchak and Bagnyukova 2006). In different populations of the same species, the levels
of TBARS can show seasonal variations. In the estuarine polychaete ( Nereis diversicolor ),
no variations were observed in the Seine estuary (Durou et al. 2007), but higher levels
were recorded in January and October at different Moroccan sites (Aït Alla et al. 2006). In
bivalves, no TBARS variations were observed in Mytilus sp. (Shaw et al. 2004; Bocchetti and
Regoli 2006), whereas their concentrations were maximum in Perna viridis during spawn-
ing in May despite a strong activation of antioxidant systems (Wilhelm Filho et al. 2001).
In marine bivalves, other environmental factors such as tidal cycles can influence lipid
peroxidation, which increases during emersion (Durand et al. 2001; Almeida et al. 2005).
On the contrary, these phases of immersion/emersion did not induce variations of TBARS
in the gastropod Littorina littorea , whose antioxidant systems neutralize ROS formation
during the aerial phase (Pannuzio and Storey 1998).
Moreover, numerous studies conducted during the past two decades in marine and
freshwater media have shown that the levels of lipid peroxidation can be affected by
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