Objective To examine the absorption, distribution and affinity with adipose tissue of microplastics (MPs) and nanoplastics (NPs) in digestive organs of mice after oral exposure.
Methods Totally 48 male Kunming mice were randomly assigned into 4 groups and exposed to normal saline and 100 nm, 3 μm, 10 μm fluorescent polystyrene (PS) beads at the dosage of 200 mg/kg by a single gavage. The specimens of stomach, small and large intestine, liver, and subcutaneous adipose tissue of the mice were collected at 0.5, 1, 2, and 4 hours after the exposures; feces in colon were also sampled simultaneously. The in vivo imaging system (IVIS) was used to determine fluorescence intensity (FI) of MPs and NPs in the specimens. Histological examinations were performed to corroborate the fluorescence intensity measurements.
Results In the mice with 100 nm PS exposure, the FI of stomach and small intestine specimens were the highest at 0.5 hour after the gavage and the FI of large intestine specimens and feces samples were significantly higher than those of the control mice 4 hours after the exposure (both P < 0.05), with a 12.79 times increased intensity for the feces samples (P < 0.05). For the mice with 3 μm PS exposure, the FI of stomach and small intestine specimens increased significantly at 0.5 hour after the treatment (P < 0.05) and the intensity of stomach specimens from the mice with 10 μm PS exposure was also increased at the time. Significant increase in FI was observed in liver specimens 4 hours after the exposure and in subcutaneous adipose tissue specimens 0.5 hour after the exposure only for the mice with 100 nm PS treatment (both P < 0.05).
Conclusion After a single oral exposure of nano-microplastics in mice, the nanoplastics could be absorbed through digestive tract and entered into liver tissues and the absorbed nanoplastics could accumulate in the adipose tissue rapidly. By contrast, the microplastics could be detected only in digestive tract 4 hours after exposure.
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