Effects of copper on calcium metabolism and detoxification mechanisms in freshwater bivalve species of Anodonta

Copper (Cu) is one of the metals contaminating European fresh water ecosystems. Filter feeding bivalves have high bioaccumulation potential for transition metals as Cu. While copper is an essential micronutrient for living organisms, it causes serious metabolic and physiological impairments when in excess. The objectives of this thesis are to get knowledge on toxic effects and detoxification mechanisms of copper in Anodonta cygnea and Anodonta anatina, two mussel species widely distributed in continental waters. Because Ca plays a fundamental role in shell formation and in numerous biological processes, Cu2+ effects on cellular plasma membrane calcium transport were studied first. In the second step, the investigations focused on Cu2+ detoxification mechanism involving cysteine (Cys) rich compounds known to play a major role in homeostasis of essential trace metals and in cellular metal detoxification. Under our experimental conditions, copper inhibition of Ca2+-ATPase activity was observed in the gills and the kidneys, and inhibition of Na+/K+-ATPase in the gills and the digestive gland (DG) upon 4 d of exposure to 0.35 micro mol/L Cu2+. At day 7 of exposure to environmental Cu2+ concentrations total recoveries was observed in the kidneys and the gills for Ca2+-ATPase activity, and in the DG for Na+/K+-ATPase, but not at high doses. Ca and Na transport inhibition may entail disturbance of osmo-regulation and lead to continuous under-supply of Ca. Recoveries of Na+/K+-ATPase and Ca2+-ATPase enzymes function suggest that metal-detoxification is induced. Phytochelatins (PC) are Cys-rich oligopeptides synthesised by phytochelatin synthase from glutathione in plants and fungi. Phytochelatin synthase genes have recently been identified in invertebrates; this allows us to hypothesize a role of PC in metal detoxification in animals. In the second part of this work, PC and their precursors as well as metallothionein were analyzed in the gills and in the DG of Anodonta cygnea exposed to Cu2+. Our results showed for the first time the presence of PC2-4 in invertebrates. PC were detected in control mussels not exposed to metal, suggesting a role in essential metal homeostasis. Compared to control, PC2 induction was observed during the first 12 h of Cu2+ exposure. Those results confirm the role of PC as a first line detoxification mechanism in A. cygnea.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Bayreuth

Year

2013

Author dc:creator

• Santini, Olivier

Contributors dc:contributor

• Frank, Hartmut

Repository record source_url

https://epub.uni-bayreuth.de/id/eprint/150/

OAI identifier oai:identifier

oai:epub.uni-bayreuth.de:150