ToxSci Advance Access published online on May 24, 2004
Toxicological Sciences, doi:10.1093/toxsci/kfh175
Toxicological Sciences © Society of Toxicology 2004; all rights reserved
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1 Research and Development, R.J. Reynolds Tobacco Co., Winston-Salem, North Carolina, 27102
* To whom correspondence should be addressed. E-mail: curting{at}rjrt.com.
Hypothesizing that their respective genetic backgrounds would confer an increased sensitivity to lung tumorigenesis, the plausibility of selected rodent models for the inhalation testing of mainstream tobacco smoke (MTS) was evaluated. Strain A/J and rasH2 transgenic (Tg) mice were exposed to MTS from Kentucky 1R4F research cigarettes using either a whole-body or nose-only exposure regimen. The whole-body regimen included a 20-week exposure period [0.200 mg wet total particulate matter/liter (WTPM/L), 6 hrs/d, 5 d/wk], while nose-only dosing proceeded for 28 weeks [0.040, 0.125 or 0.400 mg WTPM/L, 3 hrs/d, 5 d/wk]; both regimens included a 16-week recovery period. Gross and microscopic examinations of the lungs were used to evaluate tumor formation, with experimental results supporting the following conclusions: 1) evaluation of MTS-induced tumorigenicity based on gross evaluation versus microscopic confirmation provides strikingly disparate results, indicating that serial sectioning is necessary for a definitive assessment of lung tumors; 2) while the dosing regimens employed do not allow for a definitive comparison, whole-body exposure appeared to be more effective for inducing statistical changes in tumor multiplicity and incidence compared to nose-only exposure; 3) exposure-related stress, evidenced as reductions in both body weight gain and background tumor formation, represents a potential confounder during inhalation testing of MTS tumorigenicity, with additional investigation warranted in order to validate the specificity of exposure-related responses; and 4) comparative findings between A/J and rasH2 Tg mice suggest that the former may be overly sensitive to exposure-related stress, potentially influencing tumorigenic responses.
Accepted May 7, 2004
Carcinogenicity
Lung Tumorigenicity in A/J and rasH2 Tg Mice Following Mainstream Tobacco Smoke Inhalation
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