Vascular changes and liver tumours induced in mink by high levels of nitrite in feed

Two groups of female mink were fed a diet supplemented with 30-50 mg/kg bw sodium nitrite for up to six years. The first group also received dimethylamine hydrochloride. Seven male offspring from litters born in the first year were fed the same diet for nine months but showed no pathomorphological change. After three years on trial, female mink developed occlusive changes in some branches of the efferent hepatic veins, and 21% of the mink in group 1 and 31% in group 2 developed liver haemangioendotheliomas or precancerous liver changes. The pathomorphological changes were identical to those seen in animals exposed to N-nitrosodimethylamine (NDMA). This result indicates in-vivo formation of NDMA as a result of the high nitrite in the diet. However, NDMA was not measured in the blood of the nitrite-exposed mink.