Accounting for Differences in Estrogenic Responses in Rainbow Trout (Oncorhynchus mykiss:  Salmonidae) and Roach (Rutilus rutilus:  Cyprinidae) Exposed to Effluents from Wastewater Treatment Works

Abstract

Effluents from wastewater treatment works (WwTWs) contain estrogenic substances that induce feminizing effects in fish, including vitellogenin (VTG) synthesis and gonadal intersex. Fish vary in their responsiveness to estrogenic effluents, but the physiological basis for these differences are not known. In this study, uptake of estrogen from two WwTW effluents (measured in hydrolyzed bile) and estrogenic response (VTG induction) were compared in a salmonid (rainbow trout, Onchorhynchus mykiss) and a cyprinid fish (roach, Rutilus rutilus). Immature rainbow trout were more responsive than maturing roach to the estrogenic effluents. The more potent of the two estrogenic effluents (containing between 24.3 and 104.1 ng estradiol-17beta equivalents/L [E2eq/L]) resulted in a 700-fold and 240-fold induction of plasma VTG in male and female trout, respectively, but only a 4-fold induction in roach (and in males only). The less potent effluent (varying between 4.1 and 6.8 ng E2eq/L) induced VTG in the trout only, with a 4-fold and 18-fold induction in males and females, respectively. In fish exposed to tap water, the estrogenicity of the hydrolyzed bile was 0.03+/-0.01 ng E2eq/microL (for both sexes in trout), 0.18+/-0.04 ng E2eq/microL in male roach, and 0.88+/-0.15 ng E2eq/microL in female roach. The higher bile content of estrogen in control roach reflected their more advanced sexual status (and thus higher endogenous estrogen) compared with the immature female trout. In trout maintained in effluents, the bile content of estrogen was 100-fold and 30-fold higher than controls at WwTW A and B, respectively. Bioconcentration factors (BCFs) for estrogenic activity in bile were between 16 344 and 46 134 in trout and between 3543 and 60 192 in roach (no gender differences were apparent). There were strong correlations between VTG induction and the estrogenic activity of bile extracts for both trout and roach. The results confirm that estrogenic contaminants bioconcentrate to a high degree in fish bile and that the level (and nature) of this accumulation may accountfor responsiveness to the endocrine disruptive effects of estrogenic effluents. Immature fish were the more appropriate life stage for quantifying estrogen exposure and uptake in bile, as they contain little circulating endogenous oestrogen compared with sexual maturing fish. The nature of the estrogenic contaminants is detailed in an accompanying paper.

Occurrence of intersex in wild freshwater fish in Slovenian rivers: a histological evaluation

“…A recent review of 48 studies conducted in 24 countries reports intersex findings in at least 37 fish species from 17 families (29). The salmonid species, to which grayling belongs, have also been reported as more sensitive to oestrogenic exposure than the cyprinid fish (30).…”

E2, an Aquatic Hazard Worldwide

“…8, No. 10; In the natural environment, different factors may be involved in the degradation process by bacteria, such as: degradation in the anaerobic river sediments which is more rapid than in the anaerobic marine sediments (Lopez et al, 2002;Tyler et al, 2005;Czajka & Londry, 2006;Christoph & Juliane, 2009), salinity factor that makes E2 more resistant to degradation, or failing of marine microorganism to involve in biodegradation of E2 are all possible factors.…”

Chemical kinetics and interactions involved in horseradish peroxidase-mediated oxidative polymerization of phenolic compounds

“…These chemicals are frequently referred to as endocrine disrupting compounds (EDCs) based on their ability to mimic the natural estrogens found in humans and animals (Tyler et al, 2005;Purdom et al, 1994).…”