Comparison of Tissue Damages Resulting from Chronic Administration of Manganese Dioxide Nano- and Microparticles on the Liver, Kidneys and Testes of Rats

This study investigated tissue damages induced by chronic subcutaneous administration of nano- and microparticles of manganese dioxide (MnO2) on the liver, kidneys and testes of rats.

Rats (n=210) were divided into three groups: control, MnO2 nanoparticle injected and MnO2 microparticle injected. The experimental groups received subcutaneous injections with either nano- or microparticles of a solution that contained MnO2 (100 μg/kg) once per two weeks for 14 weeks. Once every two weeks, we randomly selected five rats from each group for histological evaluations of the liver, kidneys, and testes. Tissue lesions were initially evaluated by hematoxylin and eosin staining, then kidney and liver tissue sections were stained by the Jones and Masson's trichrome methods, respectively. The changes in diameter of basement membrane and cell numbers of the various parts of the nephrons in different groups were measured by Image Tools version 2 software.

The liver tissues of the nano- and microparticle groups exhibited severe damage histopathologically. Cloudy swelling was observed in the cytoplasm of hepatocytes. The liver tissue and its canaliculi structures were severely damaged. Inflammation and ductular reaction signs were seen in liver tissue. Deposition of particles in the basement membrane of the nephrons were observed in the nanoparticle-treated group. There was a significant reduction in glomerular and tubular cells in the nanoparticle-treated group compared to the control and microparticle-treated groups. Some of the structural and functional parameters of the testes in the nanoparticle-treated group had significant pathobiological variations.

Administration of MnO2 nanoparticles when compared with the same dose of MnO2 microparticles caused more tissue damage in all examined tissues. Reduction in particle size from micrometer to nanometer appeared to exacerbate the damaging mechanisms of these particles in the examined tissues.