Objective To study the distribution of cerium dioxide nanoparticles (CeO₂-NPs) in rats after 90 d oral subchronic exposure.

Methods A total of 40 male SD rats were randomly divided into four groups: control (deionized water), low dose (20 mg/kg), medium dose (100 mg/kg), and high dose (500 mg/kg), with 10 rats in each group. The rats received intragastric administration every other day for totally 90 d. All animals were sacrificed at 24 h after exposure to collect tissue (liver, kidney, jejunum, ileum, cecum) and blood samples. The content of cerium was measured by inductively coupled plasma-mass spectrometry, and the tissue samples were subjected to pathological observation.

Results Compared with the control group, the medium-dose group had significantly increased content of cerium in the jejunum, cecum, and blood (P < 0.05), and the high-dose group had significantly increased content of cerium in the jejunum, cecum, and liver (P < 0.05). Compared with the low-dose group, the high-dose group had significantly increased content of cerium in the cecum and liver (P < 0.05). Pathological observation revealed lesions dominated by chronic inflammatory cells in the mucosa of the ileum and cecum in rats treated with medium and high doses of CeO₂-NPs, but pathological changes were absent in the liver and kidney.

Conclusion After 90 d oral exposure to cerium dioxide nanoparticles, cerium mainly accumulated in the intestine, and medium- and high-dose exposure (>100 mg/kg) caused enteritis.