Mercer Robert R, Scabilloni James F, Hubbs Ann F, Wang Liying, Battelli Lori A, McKinney Walter, Castranova Vincent, Porter Dale W
Part Fibre Toxicol. 2013 Aug 9;10:38. doi: 10.1186/1743-8977-10-38.
Inhalation exposure studies of mice were conducted to determine if multi-walled carbon nanotubes (MWCNT) distribute to the tracheobronchial lymphatics, parietal pleura, respiratory musculature and/or extrapulmonary organs. Male C57BL/6 J mice were exposed in a whole-body inhalation system to a 5 mg/m3 MWCNT aerosol for 5 hours/day for 12 days (4 times/week for 3 weeks, lung burden 28.1 ug/lung). At 1 day and 336 days after the 12 day exposure period, mice were anesthetized and lungs, lymph nodes and extrapulmonary tissues were preserved by whole body vascular perfusion of paraformaldehyde while the lungs were inflated with air. Separate, clean-air control groups were studied at 1 day and 336 days post-exposure. Sirius Red stained sections from lung, tracheobronchial lymph nodes, diaphragm, chest wall, heart, brain, kidney and liver were analyzed. Enhanced darkfield microscopy and morphometric methods were used to detect and count MWCNT in tissue sections. Counts in tissue sections were expressed as number of MWCNT per g of tissue and as a percentage of total lung burden (Mean ± S.E., N = 8 mice per group). MWCNT burden in tracheobronchial lymph nodes was determined separately based on the volume density in the lymph nodes relative to the volume density in the lungs. Field emission scanning electron microscopy (FESEM) was used to examine MWCNT structure in the various tissues.
Tracheobronchial lymph nodes were found to contain 1.08 and 7.34 percent of the lung burden at 1 day and 336 days post-exposure, respectively. Although agglomerates account for approximately 54% of lung burden, only singlet MWCNT were observed in the diaphragm, chest wall, liver, kidney, heart and brain. At one day post exposure, the average length of singlet MWCNT in liver and kidney, was comparable to that of singlet MWCNT in the lungs 8.2 ± 0.3 versus 7.5 ± 0.4 um, respectively. On average, there were 15,371 and 109,885 fibers per gram in liver, kidney, heart and brain at 1 day and 336 days post-exposure, respectively. The burden of singlet MWCNT in the lymph nodes, diaphragm, chest wall and extrapulmonary organs at 336 days post-exposure was significantly higher than at 1 day post-exposure.
Inhaled MWCNT, which deposit in the lungs, are transported to the parietal pleura, the respiratory musculature, liver, kidney, heart and brain in a singlet form and accumulate with time following exposure. The tracheobronchial lymph nodes contain high levels of MWCNT following exposure and further accumulate over nearly a year to levels that are a significant fraction of the lung burden 1 day post-exposure.
进行小鼠吸入暴露研究，以确定多壁碳纳米管（MWCNT）是否会分布到气管支气管淋巴管、壁层胸膜、呼吸肌组织和/或肺外器官。将雄性C57BL/6 J小鼠置于全身吸入系统中，暴露于5 mg/m3的MWCNT气溶胶中，每天暴露5小时，共12天（每周4次，持续3周，肺负荷为28.1 μg/肺）。在12天暴露期后的第1天和第336天，将小鼠麻醉，通过全身血管灌注多聚甲醛来保存肺、淋巴结和肺外组织，同时向肺内充气。在暴露后的第1天和第336天，对单独的清洁空气对照组进行研究。对肺、气管支气管淋巴结、膈肌、胸壁、心脏、脑、肾和肝脏的天狼星红染色切片进行分析。使用增强暗视野显微镜和形态计量学方法来检测和计数组织切片中的MWCNT。组织切片中的计数以每克组织中MWCNT的数量表示，并以总肺负荷的百分比表示（平均值±标准误，每组N = 8只小鼠）。根据淋巴结中的体积密度相对于肺中的体积密度，分别确定气管支气管淋巴结中的MWCNT负荷。使用场发射扫描电子显微镜（FESEM）检查各种组织中的MWCNT结构。
在暴露后第1天和第336天，发现气管支气管淋巴结分别含有肺负荷的1.08%和7.34%。尽管团聚体约占肺负荷的54%，但在膈肌、胸壁、肝脏、肾脏、心脏和脑中仅观察到单根MWCNT。在暴露后第1天，肝脏和肾脏中单根MWCNT的平均长度与肺中单根MWCNT的平均长度相当，分别为8.2±0.3微米和7.5±0.4微米。平均而言，在暴露后第1天和第336天，肝脏、肾脏、心脏和脑中每克分别有15371根和109885根纤维。暴露后第336天，淋巴结、膈肌、胸壁和肺外器官中单根MWCNT的负荷显著高于暴露后第1天。
吸入并沉积在肺中的MWCNT以单根形式转运到壁层胸膜、呼吸肌组织、肝脏、肾脏、心脏和脑中，并在暴露后随时间积累。暴露后气管支气管淋巴结中含有高水平的MWCNT，并在近一年的时间里进一步积累，达到暴露后第1天肺负荷的很大一部分。
