The effect of N-nitrosonornicotine on the buccal mucosa of Syrian hamsters

The carcinogens in smokeless tobacco have been identified as the tobacco-specific nitrosamines and the effect of one of these, N-Nitrosonornicotine (NNN), on the buccal mucosa of the Syrian hamster was studied.

Buccal pouches of 36 Syrian hamsters were painted five times per week for 24 weeks with 10 mg/mL 98% pure NNN in suspension with mineral oil. Animals were killed at 6, 8, 12, and 24 weeks.

At 6 weeks, the buccal pouch mucosa of the experimental animals appeared clinically more hyperemic than those of the controls. From 12 weeks onward, all experimental animals showed epithelial hyperplasia and inflammation on histologic examination. Three animals killed at 24 weeks showed mild epithelial dysplasia.

Exposure of Syrian hamster buccal mucosa to NNN, five times per week for 24 weeks, did not result in clinical or histologic cancerous changes. NNN may require other factors for cancer production, such as a cocarcinogen, a higher concentration, or a longer period of application.