Mammary Tumors and Mammary Gland Development in Normal and EstrogenTreated F1 Hybrids of Strains C3H/J and RIII/An Mice2

Publisher Website
Google Scholar
Abstract
A comparison of the rate of tumor development in F1 hybrids of reciprocal crosses between the high-mammary-tumor strains C3H/HeJ and RIII/AnJ showed that the mean tumor age was higher and the incidence of mammary tumors was lower in the F1 virgins with RIII mothers than in F1 virgins with C3H mothers. Pellets composed of 20 percent diethylstilbestrol and 80 percent cholesterol were implanted subcutaneously into male and female mice and removed after 8 weeks or left in for life. The mice used were F1 hybrids of C3H/J and RIII/An with the mammary-tumor agent and F1 hybrids of agent-free strains C3HeB and RlllfB. Less than half of the untreated F1 virgins born to agent-free C3H or agent-free RIII mothers developed mammary tumors and these occurred only in old animals. Virgins exposed to diethylstilbestrol pellets for 8 weeks developed a high percentage of mammary tumors whether or not the agent was present, but they occurred at a later age in agent-free females. The tumor incidence and mean tumor age in male and female hybrids with the agent were approximately the same as in male and female hybrids without the agent when the mice were treated for life with diethylstilbestrol. This indicates that in these hybrids the mammary-tumor agent is not an important factor in tumor formation if the animals are stimulated by exogenous estrogenic hormones for a long period. Wholemounts were made of mammary glands of all groups studied. Most of the mammary glands were fairly well developed in strain RIII/An virgin females and in virgin hybrids between strains C3H and RIII.