Specific estrogen binding in rat mammary tumors induced by 7,12-dimethylbenz(a)anthracene

Experiments were undertaken with 7,12-dimethylbenz(q)anthracene-induced mammary tumors of the rat to determine whether ovarian-dependent and ovarian-independent tumors could be distinguished on the basis of differences in the estrogen binding capacity of the tumors in vitro and in vivo. Our results confirm reports showing that ovarian-depentent tumors undergo interaction between ovarian-dependent tumors undergo interaction between 17beta-(3H)estradiol and specific estrogen binding components both in vivo and in vitro, as described for other estrogen target tissues. However, our results also demonstrated that certain 7,12-dimethylbenz(a)anthracene-induced tumors, which continue to grow after ovariectomy of the host, contained significant amounts of 17beta-(3H)estradiol bound to cytoplasmic as well as nuclear components. The sedimentation properties of these components were indistinguishable from those of either ovarian-dependent 7,12-dimethylbenz(a)anthracene-induced tumors or rat uterus. The cytoplasmic binding components of both classes of tumors exhibited similar specificities for estrogens. There did not appear to be an absolute correlation between estrogen-binding capacity of a tumor and its growth response to ovariectomy.