Endocrine activities and cellular stress responses in the marsh frog Pelophylax ridibundus exposed to cobalt, zinc and their organic nanocomplexes

Abstract

Metal-containing materials are extensively used in industry, personal care products and medicine, and their release in the environment causes concern for the potential impacts on aquatic organisms. We assessed endocrine disrupting potential of N-vinyl-2-pyrrolidone-based nanoparticles (Me-PSs) containing cobalt (Co2+) or zinc (Zn2+), using the marsh frog Pelophylax ridibundus as a model. Adult males were exposed for 14 days to waterborne Co2+ (50μg/L), Zn2+ (100μg/L) or corresponding concentrations of Co-PS, Zn-PS, or parental polymeric compound (PS). The indices of thyroid activity, vitellogenesis, cytochrome P450-dependent monooxygenases activity (EROD) and cytotoxicity markers were evaluated. Exposure to Co2+ led to the elevation of serum thyrotropin (TSH) and hepatic deiodinase activities accompanied by the up-regulation of EROD activity. In contrast, the action of the polymer-containing substances (Co-PS, Zn-PS and PS) as well as free Zn2+ caused a prominent decrease of EROD activity and a decrease in serum cortisol and TSH concentrations. Exposures to Zn2+, Zn-PS and PS upregulated vitellogenesis in males. All exposures except Co2+ caused neurotoxicity as indicated by the depletion of cholinesterase. These results demonstrate toxicity of Co- and Zn-containing Me-PSs and their parental compounds (Zn2+ and PS) in frogs and indicate distinct mechanisms of Co2+ action. Broad disruption of the hormonal pathways and reduced capacity for organic xenobiotic detoxification may have deleterious impacts on amphibian populations from habitats exposed to metallorganic pollution.