Two-year intermittent exposure of a multiwalled carbon nanotube by intratracheal instillation induces lung tumors and pleural mesotheliomas in F344 rats

Table 2 Histological analysis of non-neoplastic lesions in the lung and pleura

Time-point		Week 26			Week 52			Week 104
Group		Control	Low-dose	High-dose	Control	Low-dose	High-dose	Control	Low-dose	High-dose
Number of rats examined		5	5	5	5	4	4	27	26	24
Lung	Accumulation, alveolar macrophage	1	5*	5*	0	4*	4*	6	26*	24*
	Accumulation, alveolar macrophage	[0.05]	[1.34*]	[1.86*]	[0]	[1.74*]	[2.63*]	[0.08]	[2.55*]	[2.84*]
	Focal fibrosis, alveolar wall	0	5*	5*	0	4*	4*	0	26*	24*
	Focal fibrosis, alveolar wall	[0]	[1.42*]	[1.86*]	[0]	[1.65*]	[2.56*]	[0]	[2.59*]	[3.19*]
	Granulomatous change	0	3	5*	0	4*	4*	0	26*	24*
	Granulomatous change	[0]	[0.10]	[1.12*]	[0]	[0.86*]	[1.71*]	[0]	[1.31*]	[2.52*]
	Reactive alveolar hyperplasia	0	5*	5*	0	4*	4*	0	26*	24*
	Reactive alveolar hyperplasia	[0]	[0.61*]	[1.39*]	[0]	[1.60*]	[2.04*]	[0]	[2.43*]	[2.60*]
	Bronchiolar hyperplaisa (bronchiolization)	0	4*4^a	0	0	1	4*	1	26*	24*
	Bronchiolar hyperplaisa (bronchiolization)	[0]	[0.80*]	[0.20]	[0]	[0.25]	[1.00*]	[0.04]	[2.19*]	[2.92*]
	Bronchioloalveolar hyperplasia	0	1	0	2	0	0	6	16*	22*
	Bronchioloalveolar hyperplasia	[0]	[0.20]	[0]	[0.40]	[0]	[0]	[0.46]	[1.67*]	[2.50*]
	Atypical hyperplasia	0	0	0	0	0	0	0	4	10*
	Atypical hyperplasia	[0]	[0]	[0]	[0]	[0]	[0]	[0]	[0.43*]	[0.92*]
Pleura	Infiltration of inflammatory cells	0	3	4*	0	4*	4*	0	24*	23*
	Infiltration of inflammatory cells	[0]	[0.80]	[1.00*]	[0]	[0.75*]	[1.75*]	[0]	[1.52*]	[1.92*]
	Focal fibrosis	0	2	4*	0	4*	4*	0	26*	24*
	Focal fibrosis	[0]	[0.60]	[1.40*]	[0]	[1.25*]	[1.75*]	[0]	[2.38*]	[2.75*]
	Mesothelial hyperplasia	0	0	0	0	0	0	0	9*	17*
	Mesothelial hyperplasia	[0]	[0]	[0]	[0]	[0]	[0]	[0]	[0.62*]	[1.42*]

Values show the number of animals bearing the lesion
Values in square brackets are the average severity grades in all examined animals; \(\left( {\Sigma \left( {{\text{grade}} \times {\text{number}}\;{\text{of}}\;{\text{animals}}\;{\text{with}}\;{\text{grade}}} \right)} \right) \div {\text{number}}\;{\text{of}}\;{\text{animals}}\;{\text{examined}}\)
Grade: 0, no/minimal change; 1, slight; 2, moderate; 3, marked; 4, severe
The column “week 104” includes animals that died or were euthanized before the termination
Animals bearing large granular lymphocytic leukemia (LGL) were excluded (3, 3, and 4 animals in the control, low-dose, and high-dose groups, respectively)
*Significantly different from a corresponding control group (incidence, Fischer's exact test; severity score, Steel's test)

ISSN: 1743-8977