Evaluation of Estrogenic Activities of Aquatic Herbicides and Surfactants Using an Rainbow Trout Vitellogenin Assay

Abstract

Estrogenic potencies of four herbicides (triclopyr, 2,4-dichlorophenoxyacetic acid (2,4-D), diquat dibromide, glyphosate), two alkylphenol ethoxylate-containing surfactants (R-11 and Target Prospreader Activator (TPA)), and the binary mixture of surfactants with the herbicides were evaluated using an in vivo rainbow trout vitellogenin assay. Juvenile rainbow trout exposed to 2,4-D (1.64 mg/l) for 7 days had a 93-fold increase in plasma vitellogenin (Vtg) levels compared with untreated fish, while rainbow trout exposed to other pesticides alone did not show elevated vitellogenin levels compared to the control fish. When combined with surfactants, trends indicated enhanced estrogenicity for all combinations, but only 2,4-D and triclopyr caused significant induction of Vtg. Concentration-response studies demonstrated that the lowest observed effect concentrations (LOECs) for 2,4-D and triclopyr were 0.164 mg/l and 1 mg/l, respectively. In terms of measured 4-nonylphenol (4-NP), the LOECs of R-11 and TPA were 20 micro/l and 9.5 microg/l, respectively. Binary mixtures of TPA and 2,4-D showed a greater than additive estrogenic response at the lowest concentrations tested, but a less than additive response at the highest combined concentrations. Binary mixtures of TPA with triclopyr also caused greater than additive Vtg responses in two middle concentrations when compared to TPA or triclopyr alone. When trout were exposed to water collected from a site where triclopyr was used in combination with TPA, a concentration-dependent increase in Vtg expression was observed. Measured values of 4-NP were 3.7 microg/l, and triclopyr concentrations were below detection (<5 ng/l). Estradiol equivalents (EEQs) of the lake water were calculated from an estradiol concentration-response curve and were similar (8.5 +/- 7.7 ng/l) to the mean values for the combined triclopyr + TPA treatments (9.9-12.2 ng/l) in the laboratory, suggesting the estrogenicity of the water may have been due to the treatment. These results demonstrated the binary mixture of alkylphenol ethoxylate-containing surfactants with two aquatic pesticides possessed greater than additive estrogenic responses in fish under laboratory conditions and in a field setting.

Complex contaminant exposure in cetaceans: A comparative E‐Screen analysis of bottlenose dolphin blubber and mixtures of four persistent organic pollutants

“…At concentrations above the LOECs, however, the binary mixture response was less than the simple addition of each individual component's response and at the highest concentration tested the binary mixture response was eliminated completely, suggesting that the effects of estrogenic mixtures are dose-dependent. The nonmonotonic (inverted-U shaped) dose-response relationships observed for 4,4 0 DDE, trans-nonachlor and their combination in the present study are not uncommon; similar dose-response relationships have been observed for other estrogenic compounds tested in in vitro and in vivo models [38][39][40]. The specific mechanisms mediating the reduction in cell proliferation at high concentrations observed in the present study are unknown, but could include cytotoxicity [39], and inhibition of growth due to the downregulation of E 2 receptors [41].…”

Exploring the Impacts of Two Separate Mixtures of Pesticide and Surfactants on Estrogenic Activity in Male Fathead Minnows and Rainbow Trout

“…Furthermore, there were no treatment-related histopathologic changes in fish testes or ovaries in any 2,4-D-exposed group. In contrast, induction of plasma VTG was observed in juvenile RT treated with 2,4-D, and the response was enhanced by coexposure to a commercial surfactant mixture (Xie et al 2005).…”

“…These data are compared with those from an earlier RT study that measured plasma VTG protein after treatment with 2,4-D (Xie et al 2005). One potential reason for the discrepancy may be the innate variability of VTG mRNA in liver compared with plasma VTG protein measurements in RT plasma.…”

“…Alkylphenols are typically degradation intermediates from alkylphenolic ethoxylates, which are often used in combination with aquatic pesticides, and act as dispersing agents, detergents, emulsifiers, and solubilizers (Nimrod and Benson 1996). Previous studies in RT showed that when the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was combined with a commercial alkylphenol ethothylate surfactant mixture, TPA, estrogenic activity of the mixture was greater than the that of the sum of the individual compounds (Xie et al 2005).…”

Histological analysis of acute toxicity of 2,4-diclorophenoxy acetic acid in ovary of zebrafish

“…Paul et al (2006) reported the effects of 2,4-D on several aquatic species: Brook trout (Salvelinus fontinalis), walleye (Sander vitreus), fathead minnow (Pimephales promelas), and the amphipod (Hyallela azteca) in static acute toxicity tests in the laboratory. Estrogenic activities of aquatic herbicides using rainbow trout were evaluated by Xie et al (2005). The other estrogenic compound, bisphenol A, may lead to problems in either mating or sexual behavior due to the difference in growth and disparity of sexual maturation between male and female fish (Na et al 2002).…”