Pantnagar Journal of Research

Abstract

Thirty-five Wistar rats, six weeks old, of either sex were divided randomly into two groups. Group I comprised of 20 rats as control group and group II having 15 rats as treatment group. Group II was orally administered silicon dioxide (silica) nanoparticles of 20 nm diameter in distilled water at NOAEL dose of 2000mg/kg body weight per day and were gavaged once daily for 90 days. Five rats each were sacrificed at 0 (only from group I), 30th, 60th and 90th DPT and representative tissue samples were collected at these intervals. No lesion could be observed in any organ of any rat of group I at any interval. In group II rats, liver exhibited vascular changes, mononuclear cells infiltration, dilated sinusoidal spaces, Kupffer cells hyperplasia, degeneration and necrosis of hepatocytes. Lungs revealed atelectasis, emphysema, congestion and infiltration of mononuclear cells and thickening of interalveolar septa. Kidneys showed mononuclear cell infiltration in interstitium, alterations in glomeruli, necrosis and sloughing of tubular epithelial cells and obliteration of tubular lumen. Intestine revealed increase in number of goblet cells, necrosis and desquamation of epithelium. Spleen exhibited depletion of lymphoid tissue. Heart showed vascular changes and necrosis of cardiomyocytes. There were vascular changes and mild depletion of lymphoid tissue in thymus. Brain exhibited degeneration and necrosis of neurons and neuronophagia. Ultrastructural studies in liver and kidney revealed accumulation of nanosilica in lysosomes and mitochondria, mitochondrial damage and apoptosis of hepatocytes. It can be concluded from the present studies that nanosilica exerted adverse effects on tissues of Wistar rats at NOAEL dose administered for a period of 90 days.