Endocrine disruption and health effects of caged mussels, Elliptio complanata, placed downstream from a primary-treated municipal effluent plume for 1 year.
Freshwater mussels, Elliptio complanata, were caged in special benthic pens and were immersed at one upstream (Ups) site and two downstream sites (8 and 11 km) of a primary-treated municipal effluent plume for 1 year. The levels of metallothionein-like proteins (MT), lipid peroxidation, protein-free DNA strands and glutathione S-transferase (GST) activity were assayed in digestive gland, gill and gonad tissues to evaluate biological effects and damage. The levels of monoamines (serotonin and dopamine) in nerve ganglia, ATP-dependent transport activity and monoamine oxidase (MAO) activity were also investigated in the homogenates, synaptosomes and mitochondria, respectively. Results showed that significant amounts of sediment accumulated in cages and 82% of mussels survived the yearlong exposure period at the downstream sites. MT-like proteins were induced in all tissues with the following response intensity: gill (3-fold), digestive gland (1.4-fold) and gonad tissues (1.3-fold). Lipid peroxidation decreased (2.5-fold) in digestive gland but increased in gill (1.6-fold) and in gonad tissues (1.5-fold). GST activity was readily increased in digestive gland (2.5-fold), suggesting the presence of organic contaminants in the plume. Levels of protein-free DNA strands did not vary significantly in digestive gland and gill tissues but were significantly reduced in gonad tissues (2.5-fold) relative to the upstream site. In visceral nerve ganglia, both serotonin and ATP-dependent serotonin transport decreased 1.7-fold with a 4-fold increase of 5-hydroxyindole acetate (5-HIAA, a serotonin metabolite) level relative to the upstream site. However, MAO activity was somewhat reduced at downstream sites (0.7- to 0.9-fold of the activity at the upstream site). Dopamine levels were found to be decreased (1.5-fold), but dopamine ATP-dependent transport activity was increased 1.8-fold, suggesting reduced dopaminergic activity. These results indicate that estrogenic chemicals are likely at play, and the increased dopamine and decreased serotonin ATP-dependent transport suggest that the municipal plume was serotonergic for mussels located at the downstream sites. Mussels exposed for 1 year display a complex but characteristic pattern of responses that could lead to harmful health effects including neuroendocrine disruption of reproduction.
St. Lawrence Centre, Research on Aquatic Ecosystems, Environment Canada, 105 McGill, Montréal, Québec, Canada H2Y 2E7. francois.gagne@ec.gc.ca
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F
Gagné
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Blaise
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Hellou
D000818:Animals; D049872:Bivalvia / Q000187:drug effects* / Q000502:physiology*; D004249:DNA Damage / Q000502:physiology; D004298:Dopamine / Q000378:metabolism; D005618:Fresh Water; D005982:Glutathione Transferase / Q000187:drug effects; D006066:Gonads / Q000187:drug effects / Q000502:physiology; D015227:Lipid Peroxidation / Q000187:drug effects; D008667:Metalloproteins / Q000502:physiology; D008995:Monoamine Oxidase / Q000187:drug effects; D012701:Serotonin / Q000378:metabolism; D012722:Sewage; D014874:Water Pollutants, Chemical / Q000633:toxicity*
D008667:Metalloproteins; D012722:Sewage; D014874:Water Pollutants, Chemical; D012701:Serotonin; D008995:Monoamine Oxidase; D005982:Glutathione Transferase; D004298:Dopamine