Silver nitrate damages the ovary of adult zebrafish: Evaluation of oxidative stress, expression of oxidative stress-related genes and histological changes in ovary

Abstract

Abstract Silver nitrate, a toxic compound with harmful consequences, is found in freshwater. Adult female zebrafish as an animal model was used in this study to explore the harmful effect of silver nitrate (AgNO3) on developed ovary. Zebrafish were divided in different groups and exposed to silver nitrate at concentration of 8.75, 17.5, and 35 µg/L for 28 days. Oxidative stress markers and expression of oxidative stress-related genes and histological changes in the ovary were evaluated following exposure of silver nitrate. Exposure of Silver nitrate at highest concentration significantly decreased activity of SOD and CAT and level of GSH. While CAT activity was significantly decreased at all concentrations compared to that of control group. Medium and highest concentrations significantly increased the MDA level in the ovary. The suppression of mRNA expression of the sod, cat, and nrf2 (nuclear factor erythroid 2-related factor 2) genes at medium and highest exposure levels supports the oxidative stress related alterations. Histological examination revealed a mild depletion of yolk granules in mature oocytes at 17 µg/L, and a severe depletion of yolk granules, detachment of the vitelline membrane, degeneration of the granulosa cell layer, and proliferation of interstitial connective tissue at 35 µg/L. The findings elucidated that silver nitrate damages the ovary due to oxidative stress through down-regulation of sod, cat, and nrf2 genes.