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.
Gagné
F
F
St. Lawrence Centre, Research on Aquatic Ecosystems, Environment Canada, 105 McGill, Montréal, Québec, Canada H2Y 2E7. francois.gagne@ec.gc.ca
Blaise
C
C
Hellou
J
J
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