Experimental investigations on the influence upon the chemical carcinogenesis. IIIrd communication: studies with 1,2-dimethylhydrazine.

After ten times monthly, subcutaneous, injections of 30 mg/kg 1,2-dimethylhydrazine (DMH) to Sprague-Dawley-rats, malignant tumors were found in approximately 90% of the animals after a mean induction period of approximately 330 days. Injections were started on the 2nd day of life and maintained during 10 months. 72% of the tumors induced were formed in the colon, 17% were squamous cell carcinomas of the ear duct, adenosarcomas of the kidney and hepatocellular carcinomas were found in 13 and 11% of the animals, respectively. Additional treatment with immunodepressive (cyclophosphamide, methotrexat, hydrocortisone) and immunostimulating substances (BCG, albumin, vitamin A-acid) as well as an enzyme-stimulating agent (Luminal) did not alter incidences and induction periods of tumors. After application of a vegetarian diet, the rate of liver and kidney tumors was diminished significantly and induction periods of intestinal and ear duct tumors increased.