Objective To examine the dynamic changes in total cell number and protein content in broncho alveolar lavage fluid(BALF) of rats with exposure to rare earth neodymium oxide dust(RENOD).
Methods A total of 195 healthy adult male SD rats SPF grade; body weight,(200& #177;16) g were treated by unexposed tracheal intubation perfusion. The different exposure time groups were exposed to 0.8 mL of 100 mg/kg RENOD suspension(experimental rats) and 0.8 mL of 0.9% normal saline(control rats); 15 experimental and 10 control rats were neutralized at each designed interval(at the 3rd, 7th, 14th, 21st, and 28th days after dust exposure). The different exposure dose groups were treated with 0.8 mL of RENOD at doses of 25, 50, 100, and 150 mg/kg, respectively; 15 experimental and 10 control rats were neutralized after 28 d(because the full exposure time was 28 d for the time and dose groups, the single control group was applicable to both model groups). The total cell numbers in BALF of rats were counted using a nageotte counting chamber under microscope. The contents of protein were measured by ELISA in supernatant and macrophage in BALF of rats in both the time and the dose exposure groups.
Results The total cell numbers in the experimental rats of both the different exposure time groups and the different exposure dose groups were significantly increased than those of the control rats(P< 0.05). Specifically, the total cell numbers of experimental rats in the different exposure time groups were first increased, then declined to the lowest at 14 d, and increased again thereafter, but the values at each time point were higher than those of the control rats(P< 0.05). In the different exposure dose groups, the total cell numbers of the experimental rats were gradually increased with the increasing dose and higher than those in the control group(P< 0.05). In both the different exposure time groups and the different exposure dose groups, the contents of protein in BALF supernatant and macrophage of experimental rats were significantly increased than those of the control rats(P< 0.01). The contents of protein in BALF supernatant and macrophage of the experimental rats in the different exposure time groups were first increased, then declined to the lowest at 14 d, and increased again thereafter, but were all higher than those of the control rats(P< 0.05). In the different exposure dose groups, the contents of protein of the experimental rats were gradually increased with the increasing dose and were higher than those of the control group(P< 0.05).
Conclusion Rat lung tissues exposed to rare earth neodymium oxide dust present significant changes in total cell number and protein content in macrophage and supernatant of BALF.
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