Use of vitellogenin as a biomarker for estrogenic effect: What is the baseline?

Vitellogenin
is used as a biomarker for estrogenic effect in laboratory-based
regulatory test systems OECD TGs 229, 230 and 234 and vitellogenin
levels in the plasma of juvenile or male specimens of various fish
species have also been used for monitoring estrogenic impacts in
freshwater and estuarine environments, especially in association with
discharges from waste water treatment plants. The use of any biomarker
requires knowledge about the baseline levels in an uncontaminated
environment and the present investigation was initiated to identify
baseline vitellogenin levels in juvenile brown trout Salmo trutta.
Juvenile brown trout were caught by electro-fishing from 15 sites in 12
streams of Funen, Denmark, during late September and early October
2010. The fish were brought to the laboratory, blood samples were taken
and plasma vitellogenin concentrations were determined by means of a
direct non-competitive sandwich ELISA. Vitellogenin concentrations in
the plasma of the 135 male, juvenile brown trout caught during the
investigation were all below 52 ng/ml and vitellogenin concentrations in
the juvenile, female brown trout were generally one order of magnitude
higher. The results indicate that baseline vitellogenin levels in juvenile,
male brown trout in an uncontaminated environment are below 100
ng/ml. This also indicates that most of the high values obtained in earlier
investigations (2000 to 2004) investigations could be attributed to
estrogenic exposure. Six of the streams investigated in 2004 were
revisited in the 2010 study and vitellogenin concentrations had
decreased. Between 2004 and 2010 some discharges (via septic tanks)
from scattered houses in the open land known to discharge estrogenic
activity had been removed and this may have reduced the addition of
estrogenicity to the streams.