AGE-DEPENDENT EFFECTS OF SILVER NANOPARTICLES ON THE MORPHO-FUNCTIONAL STATE OF RAT TESTES

Abstract

Nanotechnologies are widely spread nowadays. Different nanometer-sized materials – nanosheets, nanorods and nanoparticles – are already being used in different branches of medicine and industry. Among the variety of different structures, one of the most promising sources of nanoparticles is silver.

Silver has been known for ages for its specific anti-bacterial properties. That’s why silver salts are used for the treatment of different diseases. It was already shown that nano-sized silver shows even more prominent antiseptic properties, and that’s why colloidal silver is used for the wound healing, production of food and cosmetics, and as a part of household goods. It even appeared that nanosilver can be used in different detection systems, due to the specific optical properties. Expansion of the nanosilver to the different branches of medicine is limited by the fact that biological particles of nanoparticles in general and silver in specific are still not well known.

It has been already shown that metallic nanoparticles can be cytotoxic by the production of reactive oxygen species and direct binding to the macromolecules. That main flaw in the modern nanotoxicology is that toxicological studies are mainly conducted in vitro. At the same time, we do know that nanoparticles can cross different biological barriers and damage them. And because of that, the need for study of the whole-organism effect of nanoparticles emerges. That’s why our study focused on the reproductive toxicity of nanoparticles. As the morpho-functional features of the reproductive system change greatly in the course of the lifetime, we examined testicular toxicology of silver particles in the three age groups.

The experiment was conducted on the white male albino rats aged 1, 6 and 24 months (18 animals each). The experimental group received intraperitoneal injections of silver solution (1 mg/kg) for 10 days. Controls animals were injected with saline or vehicle solution (sodium polyphosphate). At the 10^th day, animals were sacrified, their left testicle was taken and routinely processed for histological examination. We measured the seminiferous tubules diameter and Sertoli cells’ nuclear cross section as markers of spermatogenesis; cross-sectional area of Leydig cells – as a marker of endocrine function.

It was found that testicles of the young animals were mainly unaffected by the silver particles – only the nuclei of Sertoli cells were slightly reduced. In the contrary, every morphometric parameter that we measured in the adult and old age groups was reduced, which indicates downregulation of testicular function. We suppose that young animals were less susceptible to the nanosilver due to the generally lower level of testicular activity.

To sum up, we showed that silver nanoparticles inhibit both spermatogenic and endocrine parts of the testis. Although the exact mechanism of such effect is to be further investigated, our results should be taken into account in the biomedical applications of nanosilver.