Retinyl acetate effects on the life span and the incidence of cryptogenic neoplasms in C3H mice.

The effect of feeding 0.02% retinyl acetate on the development of cryptogenic neoplasms and the life span of C3H/HeJ (+) mice of both sexes was studied. The survival at 105 weeks was 58% in untreated males and 28% in untreated females vs. 39% in treated males and 14% in treated females. The average weight in treated groups was also 10-15% lower. The incidence (percent) of neoplasm-bearing animals and total neoplasms was 87% and 57, respectively, in female controls vs. 93% and 55 in treated females. In male controls, these values were 57% and 39 compared with 50% and 38 in treated males. In treated animals, there was no reduction in the most common neoplasms, that is, neoplasms of the mammary gland and liver. The numbers of ovarian neoplasms and lung adenomas were slightly lower. Therefore, retinyl acetate exerted, at best, only a slight inhibitory effect on development of some types of cryptogenic neoplasms in mice.