RESUMO
Mammary carcinomas induced in rats by DMBA were divided into three types: I, hard proliferating tumors; II, tumors presenting from an early stage the first signs of cystic degeneration; III, lactating tumors. In all three types, cortisol reduced the protein content by 26%-30%. The already high tRNA methyltransferase activity in type I increased by 200% after cortisol treatment. Hormonal treatment of type II increased the previously reduced control methyltransferases by 37%. In the type III lactating tumors, the total tRNA methyltransferases were inhibited by 35% after cortisol treatment. The methyltransferases of types I and II were separated chromatographically into seven analogous peaks, while the enzymes from type III presented a modified pattern. In each case, cortisol treatment affected the activities of several methyltransferases simultaneously without obvious specificity.
Assuntos
Hidrocortisona/farmacologia , Neoplasias Mamárias Experimentais/enzimologia , tRNA Metiltransferases/metabolismo , 9,10-Dimetil-1,2-benzantraceno , Animais , Diferenciação Celular/efeitos dos fármacos , Feminino , Cinética , Neoplasias Mamárias Experimentais/patologia , Ratos , Ratos Endogâmicos , tRNA Metiltransferases/isolamento & purificaçãoAssuntos
Estradiol/farmacologia , Neoplasias Mamárias Experimentais/metabolismo , Receptores de Esteroides/efeitos da radiação , Animais , Citosol/metabolismo , Estradiol/metabolismo , Feminino , Cinética , Progesterona/metabolismo , Ratos , Receptores de Esteroides/efeitos dos fármacos , Receptores de Esteroides/metabolismoRESUMO
The determination of estradiol and progesterone receptor concentrations in mammary tumors is useful in predicting the hormone responsiveness. As this assay is carried out on tumor tissue which may have been subjected to radiotherapy, the possibility of an ionizing irradiation affecting the steroid receptor levels in neoplastic tissue should be taken into account. The steroid receptor concentrations are examined in dimethylbenz(a)anthracene-induced tumors of Sprague-Dawley rats. The estradiol and the progesterone receptor titers become reduced significantly after treatment with 20 Gray while an application with 7 Gray does not affect the titer values. After treatment of the tumor with 20 Gray, the steroid receptor concentrations decrease progressively, reaching a maximal reduction 20 to 30 days after exposure. This measured reduction in binding sites seems to be the result of a specific irradiation effect and not due to a possible increase in lytic enzyme levels in the regressing tumors. As radiation treatment affects the receptor concentrations, this should be kept in mind when interpreting the steroid receptor concentrations.