Relative Role of Milk Agent and Tissue Sensitivity in Estrogen Induced Mammary Growth ∗

Summary

The mammary glands of ovari—ectomized mice of strains Z, D2 and A possessing the milk agent were more susceptible to estrogenic stimulation than the breasts of mice of the same strains raised for many generations without the milk agent. However, strain differences in the mammary response to the estrogen continued to exist also in the absence of the milk agent. These variations are considered to be due to strain differences in the susceptibility of the target tissue to hormonal stimulation.