Histological alterations in male A/J mice following nose-only exposure to tobacco smoke.
The incidence and multiplicity of grossly observed and microscopic lesions of the respiratory tract of A/J mice exposed nose-only to mainstream smoke (50, 200, or 400 mg total particulate matter/m3 from 2R4F cigarettes) was compared to those of filtered air controls. Animals were necropsied at the end of exposure (5 mo) or following 4 or 7 mo of recovery. Lungs were visually inspected for tumors at all necropsies and examined histopathologically at 9 and 12 mo. At 5 mo no tumors were recorded. No significant elevations in tumor incidence or multiplicity were recorded although at 9 mo multiplicity was elevated in the mid-exposure group (0.90 versus 0.55 tumors per animal for controls). At 12 mo, multiplicity was increased over the 9-mo necropsy at all exposures except 200 mg/m3; however, there were no dose-related trends in multiplicity or incidence. Histopathological alterations included hyperplasia, metaplasia, and inflammation of the nose and larynx and proliferative lesions of the lungs. At 9 mo, the multiplicity of focal lung lesions was 1.4 per animal in controls but averaged 1.0 among smoke-exposed groups. There was an inverse relation (p < .059) between smoke concentration and the percentage of hyperplastic lesions at 9 mo. At 12 mo the high-exposure group had slightly increased multiplicity of 2.3 lesions compared with 1.6 among controls, while the percentage of hyperplasic lesions was similar between groups. Nose-only inhalation of mainstream tobacco smoke resulted in chronic inflammatory changes of the respiratory tract yet failed to produce statistically significant changes in tumor incidence or multiplicity.
Hamm
J T
JT
Lorillard Tobacco Company, Greensboro, North Carolina 27420, USA. jhamm@lortobco.com
Yee
S
S
Rajendran
N
N
Morrissey
R L
RL
Richter
S J
SJ
Misra
M
M
D000236:Adenoma / Q000209:etiology; D000818:Animals; D001835:Body Weight; D006965:Hyperplasia; D019570:Inhalation Exposure; D008168:Lung / Q000473:pathology; D008175:Lung Neoplasms / Q000209:etiology; D008297:Male; D051379:Mice; D009666:Nose / Q000473:pathology*; D009929:Organ Size; D052638:Particulate Matter / Q000032:analysis; D012137:Respiratory System / Q000473:pathology*; D012906:Smoke / Q000009:adverse effects*; D062789:Tobacco Products
D052638:Particulate Matter; D012906:Smoke