ABSTRACT
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 microg/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
ABSTRACT
Recently, applications of MnO[2] nanoparticles and microparticles in industry, pharmacology, and medicine have considerably expanded. Mn distribution and clearance from brain and spinal cord tissue compared with muscle tissue of rats after single subcutaneous injection of nanoparticles and microparticle of MnO[2]. Pain sensory threshold of rat was evaluated as neurologic consequence of the particles on CNS activity of rats. Rats divided to control and two experimental groups. Each experimental group received a single subcutaneous injection of MnO[2] nano- and microparticles, respectively. Acute pain thresholds of rats were evaluated by tail immersion method and its weight gain was recorded during these weeks. Samples taken from brain, spinal cord and muscle tissues of rats, once every 2 week for 8 weeks. The tissue Mn level was measured by inductively coupled plasma-mass spectrometry method. Both particles size passed from blood barriers. Unlike brain tissue, manganese completely cleared from spinal tissue after 8 weeks in both groups. Clearance of Mn from muscle tissue is not complete in both of the groups. Weight gain of rats in both groups was slower than control rats. In microparticle group, rats showed progressive analgesia [p<0.05]. In nanoparticle groups, rats showed hyperalgesia for first 4 weeks and analgesia during remaining weeks. Change in MnO[2] particles size affect on Mn distribution and clearance from central nervous system. Effect of particles on whole body metabolism varied with its size too. Finally, comparison of pain response of rats among particle treated groups indicates that neurobiological mechanism affected by particles is varied with their size during times after administration