Influence of hormonal alteration of host on estrogen-binding capacity in 7,12-dimethylbenz(a)anthracene-induced mammary tumors.

The estrogen-binding capacity of mammary tumors induced by 7,12-dimethylbenz(a)anthracene was measured in lesions from animals after the ovariectomy, deprival of insulin (diabetes), or treatment with lergotrile mesylate to inhibit prolactin secretion. The average estrogen-binding capacity was 30 fmoles/mg cytosol protein in growing or static carcinomas from intact (control) animals. A significant reduction in estrogen-binding capacity was observed in regressing but not static mammary tumors from ovariectomized animals. In regressing and static tumors from diabetic rats, estrogen-binding capacity was significantly lower than in lesions from intact animals; this effect was not seen in growing tumors from diabetic rats. Tumors that were growing or static in lergotrile-treated animals showed reduced capacity to bind labeled estradiol. The effects of duration of hormone treatment or time of tissue storage on estrogen-binding capacity were examined and did not appear to be correlated with the decreased binding in tumors from treated animals. The results suggest that hormones capable of producing altered neoplastic growth may influence the level of estrogen receptors.