Wild Yellow Perch (
Perca flavescens
) Oxidative Stress
Induced by Cadmium and Low Selenium Exposures
Dominic E. Ponton, Antoine Caron, Landis Hare and Peter G.C. Campbell
INRS-ETE, Quebec City, Quebec, Canada
44% of the yellow perch collected suffer lipid peroxidation (high [MDA]). High proportions of GSSG relative to GSH indicate the presence of free radicals.
Proportion of GSSG is related to the [Se] in the HSP fraction, which suggests that higher [Se] reduced oxidative stress
Fish suffering oxidative stress have higher concentrations of Cd and Zn in sensitive cell fractions (HDP+Organelles) compared to those
in the detoxified (HSP) fraction
We used this equation to quantify Cd and Zn spillover:
[Se] in the liver is negatively correlated with lipid peroxidation Our study is the first to observe an antagonist effect in nature
between selenium and a metal other than mercury [MDA]
(µmol g-1) [MDA]
(µmol g-1)
GSH/GSSG % GSSG
Abstract
Yellow perch (
Perca flavescens
) collected from lakes in the mining regions of Sudbury (ON) and Rouyn-Noranda (QC) display wide ranges in theirconcentrations of trace elements (Cd, Cu, Ni, Se, Tl and Zn). To determine if these fish are suffering oxidative stress, we measured the concentrations of glutathione (GSH), its disulfide (GSSG) and malondialdehyde (MDA). We conclude that 44% of the individuals collected from eight lakes were at
risk of cellular oxidative stress and lipid peroxidation. However, selenium appears to act as an antioxidant because higher fish selenium
concentrations were coincident with lower proportions of GSSG as opposed to GSH and lower concentrations of MDA. Furthermore, fish suffering
oxidative stress had higher proportions of some trace metals (Cd and Zn) in sensitive subcellular fractions (organelles and heat-denatured proteins), which suggests that oxidative stress causes the release of these metals
from metal-binding proteins and that Cd further exacerbates the negative effects of the low Se exposure.
Introduction
• Selenium in high concentrations in some metal-contaminated lakes.
• Selenium can be toxic, but can also protect from metal-induced effects because it can act as an antioxidant.
Homogenate Debris Membranes Nucleus Granules 800 x g
Cytosol and organelles
100 000 x g
Organelles Cytosol
Pellet Supernatant
Heat Denatured Proteins Heat Stable Proteins
10 min. at 80oC 60 min. at 4oC 50 000 x g Pellet Supernatant [GSSG], [GSH] and [MDA] Pellet Supernatant
Results and Discussion
0 10 20 30 40 50 60 70 0 1000 2000 3000 4000 5000 0 500 1000 1500 2000 2500 3000 3500 Dufa ult Dup rat Kinoje vis
OsiPeskolletie r RouynTiltHaonnna h KellyLohi McFa rlane 0 50 100 150 200 250 300 Dufa ult Dupra t Kinoje vis
OsiPeskolletie r RouynTiltHaonnna h KellyLohi McFa rlane 0 10 20 30 40 50 60 70 Dufa ult Dupra t Kinoje vis
OsiPeskolletie r RouynTiltHaonnna h KellyLohi McFa rlane 0 100 200 300 400 500 600
Cu
Zn
Se
Tl
Ni
Cd
a ac a bc b bc c ab a a b b b a a a b a a b 0 20 40 60 0 2 4 6 8 [MDA] < 51 µmol g-1 Dufault Duprat Kinojevis Osisko Pelletier Rouyn Sudbury: MF, LO, HA r2 = 0.43 0 10 20 30 40 50 0 2 4 6 80
2
4
6
8
10
0
10
20
30
40
50
% GSSG[Se] HSP (nmol g-1 protein)
0 200 400 600 0 2 4 6 8 [MDA] (µmol g-1) 0 200 400 600 0 2 4 6 8 ∆ [Cd] (nmol g-1) [MDA] (µmol g-1)
[Se]liver (nmol g-1)
0 20 40 60 80 0 50 100 150 200 250 300 350 0 20 40 60 80 100 120 140 160 180 2000 4000 6000 8000 10000 [Cd] HDP+Org. (nmol g-1) [Zn] HDP+Org. (nmol g-1) [Cd] HSP (nmol g-1) [Zn] HSP (nmol g-1) r2 = 0.22 r2 = 0.37 [Trace element] liver (nmol g-1)
∆[M]
= [M]
HDP+ [M]
Org.– (a
m[M]
HSP+ b
m)
r2 = 0.37Trace element concentrations in yellow perch liver vary widely among lakes
Cd spillover is positively related to lipid peroxidation
r2 = 0.37
Methods
Field
We collected 1-8 yellow perch in each of 11 lakes and froze their livers in liquid nitrogen.
Laboratory
We separated individual livers into 5 pieces.
We measured: trace elements, malondialdehyde (MDA), glutathione (GSH) and glutathione disulfide (GSSG).
We separated liver cells into fractions and measured trace elements
in heat-denatured proteins (HDP), organelles (Org.) and heat-stable proteins (HSP).
O2 O2- H 2O2 SOD Catalase GPx-Se GSH GSSG 2H2O H2O+1/2 O2 Cd GST
