Effects of zinc oxide nanoparticles and zinc sulfate on the testis of common carp, Cyprinus carpio.

The present study analyzed the effects of zinc oxide nanoparticles (ZnO-NPs) and zinc sulfate (ZnSO4) in the testis of six-month-old common carp Cyprinus carpio exposed to three different doses, viz., 10, 50, and 100 μg/L for 21 days. Characterization of ZnO-NPs was done after sonication, the size and shape of ZnO-NPs were determined as ∼20-30 nm spherical structure measured zeta potential of +26.0 mV. After treatment, determination of zinc (Zn) concentration in the testes revealed desired impact of the exposure. Expression of several transcription factors and few steroidogenic enzyme genes in the treated testis showed significant downregulation than the control. Measurement of oxidative stress-related enzymes such as catalase, superoxide dismutase, and glutathione-S-transferase revealed substantial elevation in the testis of treated groups when compared to control. Histological analysis of testis exhibited dose-related response, defective lumen, and slow progression of spermatogenesis. Exposure of both the forms of Zn on TM3 Leydig cell culture displayed loss of adhesion, clumping with decreased viability, and a significant increase in the apoptotic cells. In addition, comet and intracellular reactive oxygen species (ROS) assays authenticated DNA damage upon treatment with a significant increase in ROS. Histological analysis after treatment withdrawal showed revival of testis in carp to rescue the effect. Thus, the present report highlights the adverse effect of Zn on the testis function in common carp as well as evident drastically toxic in in vitro cultures.