Effect of orally administered silver nanoparticles on histological alterations in Wistar rats

The present study aimed to evaluate the histopathological effects of orally administered silver nanoparticles (AgNPs) at the No-Observed-Adverse-Effect Level (NOAEL) in Wistar rats over a 90 days period. Thirty-five healthy, six-weeks-old Wistar rats of both sexes were randomly divided into two groups: Group I (control, n=20) and Group II (treatment, n=15). Rats in Group II received AgNPs suspended in distilled water at a NOAEL dose of 30 mg/ kg body weight/day via oral gavage for 90 consecutive days. Five rats from each group were sacrificed at 0 (only from Group I), 30th, 60th, and 90th days post-treatment (DPT), and tissue samples were collected for gross and histopathological examination. No lesions were observed in any organs of the control group throughout the study. In contrast, treated rats exhibited gross lesions such as red patches on the liver, discoloration in the lungs, and mild cardiac congestion. Histologically, the liver showed congestion, thrombus formation, and hepatocellular degeneration; lungs revealed thickened interalveolar walls, emphysema, congestion, and increased mononuclear cell infiltration. Kidneys demonstrated congestion, interstitial hemorrhages, and coagulative necrosis of tubular epithelial cells. Other organs including the spleen, uterus, and testis did not show any significant lesions. These findings indicate that chronic oral exposure to nanosilver, even at NOAEL levels, can induce adverse histopathological changes in vital organs of Wistar rats.