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Among the main conclusions of the study, it should be noted that the form of metal (soluble or nanoparticles) that silver absorbs into water influences the distribution of the metal in fish organs.
At the same time, soluble silver was also found to induce short-term (three-day) alterations and long-term alterations of nanoparticles (21 days). In both cases, the animals purified themselves of the money accumulated in their bodies after spending six months in clean water, although gill inflammation remained after being exposed to the metal.
In the study, led by Amaia Orbea, three groups of 50 to 60 adult fish were used in three aquariums. Silver nitrate was added to the first reservoir to produce silver soluble in water; Silver nanoparticles at 20 nm were added in the second; and clean water was added to the third, which served as a control.
The groups in the contaminated reservoirs remained exposed to both metal forms for 21 days before spending six more months in clean water to study the consequences of a long – term exposure to water. money. An environmentally significant metal concentration has been used – a concentration that could be found in nature, for example at the sewage treatment plant outlet. The accumulation of a substance is the first step for intoxication to occur.
After three and 21 days of exposure to silver and after six months in clean water, various chemical and biological analyzes were performed on the gills, liver and intestines of the fish. The research team has selected the gills because it is the main route of entry of contaminants. the liver as it is the main organ of metabolism and detoxification; and the intestine, because silver nanoparticles can be absorbed by food.
It can be deduced from the analyzes that fish accumulate concentrations of similar metals after being exposed to soluble silver and silver nanoparticles and that after six months in clean water, initial metal concentrations were recovered.
The conclusions differed when fish organs were analyzed. The distribution of silver in the liver and intestines depended on the type of metal used in the treatment, but both treatments resulted in inflammation of the gills in the fish, an effect that remained even after six months in the first year. clean water.
In addition, liver transcriptome analysis revealed a strong impact of exposure to money.
The effect of soluble silver was more intense after three days of exposure when changes were detected in the expression levels of a total of 410 gene sequences.
In the case of silver nanoparticles, the alteration was detected 21 days later and affected 799 sequences.
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