N-Nitrosodimethylamine and 7-methylguanine DNA adducts in tissues of rats fed Chinese salted fish

Previous studies have demonstrated that rats fed Chinese salted fish developed carcinomas of the nasopharynx and nasal cavity. In the present work the contents of nitrosamines in salted fish from the city of Guangzhou, southern China, and the contents of nitrosamines and possible nitrosamine-induced DNA adducts in organs of rats fed the fish were analysed. Similar levels of N-nitrosodimethylamine (NDMA) were detected in tough and soft salted fish. The NDMA content in steamed fish was higher than in raw fish. In vitro incubation of salted fish with gastric juice significantly increased the level of NDMA. NDMA was found in liver and kidney from rats fed salted fish for 2 years, but no dose-dependence was found between salted fish treatment and NDMA content. The level of 7-methylguanine in rat liver DNA was found to be slightly higher than in DNA from nasopharynx. However, there were no significant differences in the level of 7-methylguanine in DNA samples from rats fed salted fish and rats fed standard diet.