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(185) Disruption of steroid synthesis: An environmentally relevant mechanism of endocrine modulation.
Hecker, Markus*,1, Karbe, Ludwig2, 1 Michigan State University, East Lansing, MI, USA2 University of Hamburg, 22765 Hamburg, Germany, Germany
ABSTRACT- The 1990s have witnessed a great expansion of interest regarding implications for exposure of man and wildlife to potential environmental endocrine disruptors. However, most of the studies conducted in this concern focused on the exposure to estrogenic compounds. This study demonstrates, that under complex low level exposures effects such as the modulation of steroid synthesis pathways may be of much higher relevance than the estrogenic ones. Wild bream (Abramis brama [L.]) were collected from six different sites influenced by different sources of endocrine-active substances along the Elbe river, Germany. A lake that received no domestic or industrial discharges was investigated as a reference site. Effects on sex steroid synthesis were determined by measuring aromatase activity, plasma sex steroids concentrations of 11-ketotestosterone, testosterone and 17-estradiol. Furthermore, the same fish were analyzed for biological markers of steroid action such as secondary sex characteristic (prominence of spawning tubercles), vitellogenin production and gonad growth. Significantly reduced plasma estradiol (females) and 11-ketotestosterone concentrations (males) were observed in bream from the middle Elbe, which were 10 to 40 times below concentrations in the controls. No such effects occurred for the precursor testosterone, indicating a selective mechanism of suppression of the last steps in sex steroid synthesis. This is revealed by a corresponding reduction in aromatase activity. It is strongly indicated that these inhibitory influences on the steroidogenic pathways resulted in the disturbances of sexual functions and serious inhibition of gonad growth/maturation observed at the same site. The area where inhibition of aromatase activity occurred was in accordance with a region characterized by an elevated exposure to a series of different pollutants. However, it remains difficult to clearly correlate the observed effects to a single or group of chemicals as there are still insufficient chemical analyses in the field of compounds that are reported to interfere with the aromatase activity.
Key words: wild fish, endocrine disruption, biomarker, steroid synthesis
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