Development of Sarcomata in the Livers of Albino Rats Given Sodium Nitrite and Dimethylamine (Report 1)

It is a well-known fact that dimethylnitrosamine (DMNA) causes the formation of liver cancer. And it is also recognized that DMNA is generated from dimethylamine in food and nitrite, a food additive, and that it is produced secondarily in the stomach. But there is a report that shows that albino rats practically given dimethylamine and sodium nitrite have developed no cancer. Therefore, in order to see whether the report is right or not, the present authors kept albino rats for 78 days giving them various degrees of concentration of sodium nitrite and dimethylamine solutions diluted with drinking water. As the result, no formation of tumours was found in the livers of those rats. But the decrease in the vitamin A content of their livers was observed, which suggested the disturbance of the liver function. Then in expectation of the probability that a longer period of administration of sodium nitrite and dimethylamine and a higher concentration of sodium nitrite might develop liver cancer, the authors kept rats for 410 days giving them higher concentrations of sodium nitrite (15 g/l and 30 g/l) as well as an ordinary concentration of it (5 g/l ), together with dimethylamine. The rats given sodium nitrite at higher concentrations died of methaemoglobinemia in a week or two, but the ones given at an ordinary concentration survived. One rat died on the 318th day, in whose liver a tumour was observed to have grown. Some tumours were also found in the spleen and the mesentery, which are considered to be metastatic tumours. One of the animals killed on the 410th day was found to have developed a tumour in the liver alone, which suggests that these tumours were liver-idiopathic. These tumours are conjectured through a pathohistological examination to be fibrous sarcomata of vascular origin. Judging from these results, the warning that these substances in food, i.e. dimethylamine and sodium nitrite, when they are ingested for a long time regardless of their quantities, will possibly cause the development of tumours in the liver cannot be disregarded