Vitamin A and its inhibitory effect as tested on Egyptian toads

Neoplasms of the liver were induced in 18 cases out of 44 in the Egyptian toad, Bufo regularis, by injection with 20-methylcholanthrene. Dose level was 10 mg/50 g body weight once a week. However, the injection of the same dose level of this hydrocarbon together with vitamin A palmitate on the level of 20,000 IU/50 g body weight once a week was found to develop hepatomas in the liver in only 1 of 45 cases. Results of this study indicate that vitamin A palmitate inhibited the carcinogenic effect of 20-methylcholanthrene.