History of Biomarkers - Ecological Biomarkers: Indicators of Ecotoxicological Effects - page 27

production and breakdown of natural hormones and modify levels and function of hor-
mone receptors.
When exposed to estrogens and “mimetic estrogens,” the liver synthesizes vitello-
genin (VTG), a lipoglycophosphoprotein (which is a precursor of yolk egg reserves)
specific to females, regardless of the age of fish. VTGs are high-density (300-600 kDa,
according to species) glycolipophosphoproteins having Ca and Zn ligands and are con-
sidered to have similar characteristics in vertebrates, such as fish (Nagler et al. 1987),
and invertebrates, particularly mollusks (Blaise et al. 1999). The “estrogen mimics”
exert a feminizing action, thus concerning a priori more male individuals with VTG
induction, oocyte and oviduct presence in the testes, fecundity decrease, modification
of the sex ratio, and reduction in the secondary sexual characters in the male (Tyler and
Routledge 1998).
However, field measurements of effects on the reproduction of fish are far from clear; a
full demonstration of any effect on fecundity and reproduction, size, or structure of fish
populations indeed requires field investigations that are time consuming and spatially
limited. The feasibility of the measurement of VTG and the interpretation of histological
slides of gonads of male fish collected from French rivers was studied in the chub ( Leuciscus
cephalus ) (Flammarion et al. 2000). First results have been followed by a large-scale field
experiment with this species. Measurements have demonstrated moderate but significant
VTG induction in chub collected downstream from large towns in France (Paris or Lyon).
Iwanowicz et al. (2009) evaluated the reproductive status of smallmouth bass ( Micropterus
dolomieu ) in the upper Potomac River and its tributaries. They noted the presence of imma-
ture female germ cells (oocytes) in the testes of some of the male fish. Further evidence
of endocrine disruption occurred when the authors detected the presence of VTG in the
blood of male fish. In addition to the effects on male fish, a substantial decrease in VTG in
females also suggested endocrine disruption. At present, VTG is considered a biomarker
of endocrine disruption in fish and some mollusks. In the freshwater mussel ( Elliptio com-
planata ), VTG concentrations in hemolymph and gonad increase after exposure to effluents
from wastewater treatment plant (Gagné et al. 2001).
2.4.3 Lysosomal Membrane Stability
It is known that lysosomes play a significant role in the catabolism of cellular compounds,
the intracellular transport of macromolecules, and the storage of metals (Viarengo et al.
1984) and of organic contaminants (Moore 1988). The lysosomal membrane is weakened in
the liver or digestive gland of animals subjected to pollution. It is very difficult to evaluate
the molecular changes affecting the permeability of the lysosomal membrane. Analyses
of this permeability require extremely purified preparations of lysosomal membrane and
their study at a molecular level (see Chapter 5). An easier way to evaluate this parameter is
to examine whether its physiological function is changed or destroyed following an expo-
sure to pollutants. Cytochemistry is the relevant tool that links descriptive morphology
and biochemistry to observe such pathological modifications. This technique was used
successfully to estimate the integrity of the lysosomal membrane by visualizing the hydro-
lytic enzymes inside the lysosome, and it proved to be a fast and sensitive research tool to
evaluate the effects of different xenobiotics (Pellerin-Massicotte and Tremblay 2000). This
unspecific response intervenes in all cellular types from fungi to vertebrates. Viarengo et
al. (1995) showed that a short-term exposure to pollutants in micromolar amounts (ionic
copper Cu 2+ , dimethylbenzoanthracene, and Aroclor 1254) reduced the stability of the
lysosomal membrane (LMS) of the digestive gland of mussels M. galloprovincialis . Broeg et