Cytoplasmic estrogen receptors (ER) concentrations were measured in DMBA-induced rat mammary tumors from intact, non ovariectomised (48 tumors) and ovariectomised (43 tumors) rats. Histological data permitted to distinguish malignant carcinomas (Ca) from benign tumors as well as evaluate their proliferative state. Ca were defined as proliferative or regressed whether they were characterised by numerous or a total absence of mitoses respectively. Proliferative/regressed Ca contained differentiated areas of the two former classes. All benign tumors showed a proliferative pattern. A good correlation between this histological classification and the in vivo growth behavior was established. Both in Ca and benign tumors, a reduction of ER-positive tumors occurred after ovariectomy. In Ca from intact rats, ER concentrations varied over a wide range of values from 15 to 205 fmoles/mg protein. After the operation, they varied from undetectable to 88 fmoles/mg protein. Benign tumors from intact and ovariectomised rats contained similar amounts of ER which were low on the average (0–44 fmoles/mg protein). On the average, no difference was found between ER concentrations in proliferative and proliferative/regressed Ca. Regressed Ca contained lower amounts of receptors than the two former classes. ER concentrations in pooled proliferative and proliferative/regressed Ca were significantly higher in intact than ovariectomised rats. These data concur to suggest that ovarian dependent tumors contain, on the average, higher ER concentrations than ovarian independent ones.

Keywords:
Estrogen receptors, DMBA, Mammary tumors, Ovariectomy, Histology
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© 1977 S. Karger AG, Basel
1977
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