Extrapulmonary Translocation of Ultrafine Zinc Oxide Particles Following Nose-only Exposure and Intratracheal Instillation
Date Issued
2009
Date
2009
Author(s)
Chang, Chun-Nung
Abstract
Nano-sized zinc oxide was applied in industries extensively, and many workers are exposed to zinc oxide directly or indirectly in factories, production facilities, and in operation where zinc oxide was proceeded, used, disposed, or recycled concurrently. However, there are literatures indicating that nano-sized particles may induce inflammation, thrombosis and cardiovascular diseases, or even penetrate into systemic circulation and redistribute to secondary organs. In our study, the aims were set to explore the zinc translocation in systemic circulation, characterize the distributions of the zinc levels in rat organs after exposing to fine and ultrafine particles intratracheally, and provide relevant the parameters for further kinetics studies.Seven-week old male Sprague-Dawley (SD) rats were used in this study. This study was conducted in two parts. In the first part, study animals were exposed to clean air for 1 hour and then exposed to airborne zinc oxide for 4 hours. Continuous microdialysis sampling was performed during the exposure experiment. On the other part, we intratracheally instilled ultrafine and fine zinc oxide particles of 50 nm and 325 Mesh, respectively, in PBS solution to the study animals at a dose of 5mg/kg, with three animals per group. Rats were sacrificed at 3, 6 ,12 and 24 hours post exposure, and the zinc concentrations in whole blood, plasma, serum, heart, lung, liver, kidney and dialysates of the study animals were determined by inductive coupled plasma mass spectrometry (ICP-MS) following the pretreatment process of freeze-drying and microwave digestion.he results of microdialysis revealed that in vitro recovery rate for zinc oxide was only 4.3%, and no obvious trend for zinc levels in dialysate with times was observed. In addition, the high zinc background level in the study animal might interfere with the results of zinc analysis. In the part of intratracheal instillation study, zinc levels were found elevated in serum, whole blood and liver in both ultrafine and fine zinc oxide particle exposure groups. However, there was no obvious trend for plasma, heart, lung and kidney samples. The difference in zinc levels in organ and tissue samples between these two exposure groups was not statistically significant.The results indicated the application of microdialysis in inhalation study was not successful in this study. The elevations of zinc levels in serum, liver with time after exposing to nano-sized zinc oxide particles intratracheally supported that the particle translocation happened to systemic circulation, although the trends were not obvious. The elevation of zinc level in liver is probably attributed to the systemic translocation. However, another speculation is attributed to the absorption from gastrointestinal system while intratracheal instillation. Further study needs to clarify the exposure routes for zinc oxide particulates. Isotope technology is considered to be applied in the future study to differentiate the inhaled zinc content during experimental study from the background levels in organism. In general, the findings in our study provided preliminary information on the distribution of nano-sized ZnO particle in experimental animals after inhalation exposure for risk assessment.
Subjects
Zinc oxide
nano-particle
microdialysis
intratracheal instillation
SDGs
Type
thesis
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