A synergistic effect of nitrosodimethylamine on sterigmatocystin carcinogenesis in rats.

In a study of a possible syncarcinogenic effect of nitrosodimethylamine (NDMA) on sterigmatocystin ISTG) carcinogenesis. male rats were fed diets containing I 0 ppm STG. 10 ppm STG and I ppm NDMA. I ppm STG and IOppm NDMA or JOppm NDMA for 54 wk. Hepatic carcinomas developed in 75° o of the rats fed 10 ppm STG plus I ppm NDMA and in 53";, of those fed 10 ppm STG alone. The hepatic carcinomas developed more rapidly in the former group. Abou/'50"" of the hepatic carcinomas induced by STG or STG plus NDMA showed a tubular arrangement of tumour cells. Ultrastructurally, a mixture of the characteristic organelles of hepatocytes and ductular cells were frequently found in the same cells. Throughout the experiment. proliferation of smooth endoplasmic reticulum was observed in the hepatocytes of rats fed with NDMA. Between wk 54 and 69. Leydig-cell tumours developed in 47. 45 and I 5";, of the animals on the 10 ppm NDMA plus I ppm STG and the I ppm NDMA plus 10 ppm STG diets. respectively. Although, at this level. NDMA alone did not induce hepatic carcinomas. it may have a role in STG-carcinogenes.is in the liver. as an inducer of carcinogen-activating enzymes.