Differences in the response to oxidative stress and mutant frequency in CD (Sprague-Dawley) and Fisher 344 rats due to an induced inflammatory response.

In this study, the rodent air pouch model was used to examine the production and processing of oxidative DNA damage in two strains of rats commonly used in toxicity testing. An inflammatory response was induced by injecting zymosan A (50 mg) into an air pouch on male CD (Sprague-Dawley [S-D]) and Fisher 344 (F-344) rats, and the animals were then sacrificed at 1, 3, 7, 14, and 28 days (n = 6 per time point per strain). Tissues from the lining of the air pouch were collected for 8-hydroxy-2'-deoxyguanosine (8-OH-dG) analysis and for paraffin embedding. Significant (P < 0.01) increases in 8-OH-dG were observed after 1 day in the DNA from cells lining the air pouch of zymosan A-treated versus control S-D (101.5 +/- 27.1 vs. 23.1 +/- 2. 7 8-OH-dG/dG x 10(5)) and F-344 (51.4 +/- 5.3 vs. 14.4 +/- 0.6 8-OH-dG/dG x 10(5)) rats. By 28 days, 8-OH-dG levels had returned to background in S-D rats, but remained elevated in F-344 rats. The frequency of apoptosis was evaluated using the in situ end-labeling (TUNEL) assay, which revealed that zymosan A-treated S-D rats had a significantly (P < 0.05) higher frequency of apoptosis compared to zymosan A-treated F-344 rats. To examine the potential consequences of these differences in endogenously produced DNA damage and apoptosis, we measured mutations at the hprt locus in fibroblasts of the pouch lining and observed a significant (P < 0.05) increase in the mutant frequency at day 28 in F-344 rats (54.2 +/- 13.6 mutants per 10(6) cells) compared to controls (4.5 +/- 2.0 mutants per 10(6) cells). The mutant frequency was not increased in S-D rats. These data demonstrate that strain differences in the production and processing of oxidative DNA damage due to an inflammatory response may impact the long-term pathologic consequences of chronic inflammation. Environ. Mol. Mutagen. 35:336-342, 2000 Published 2000 Wiley-Liss, Inc.