Postnatal carcinogenic study of 1,2-dimethylhydrazine dihydrochloride in rats.

The outbred SPF rats of the Ripb: Wist stock were applied subcutaneously 1,2-dimethylhydrazine dihydrochloride (DMHD) at a concentration of 0.036% and 0.144% from the first day of age after the birth. In nine experimental groups DMHD was administered for first 5, 10, 15 and 20 days of age after the birth at total doses of 0.36 to 2.16 mg. With the highest applied dose, all animals died during the treatment, further deaths were recorded in groups in which DMHD was administered for first 5 to 10 days. The maximum length of survival was one year. The conclusion of the study was achieved only by the control animals and by 36.6% of males and 13.8% of females of the experimental group. From the 24th week of age, hepatic and renal tumors were detected in rats. In the liver hepatocellular carcinomas and benign hepatomas occurred, and were found in all groups which had been applied DMHD, furthermore cholangiomas, mostly in the groups which had been applied DMHD up to the age of 15 days and cavernomas in the groups which had been applied DMHD up to the age of 20 days. Practically in all rats which had been administered DMHD focal preneoplastic hyperplasia of liver cells was detected. In the kidney always a mixed malignant mesenchymal tumor was found in all animals of the groups treated up to age of 15 days.