Tissue- and time-dependent estrogen receptor activation in estrogen reporter mice.

With the aim of developing an in vivo model that directly detects activation of estrogen receptors (ERs), transgenic mice carrying a luciferase reporter gene were generated. The luciferase reporter gene was under the control of three consensus estrogen-responsive elements (EREs) coupled to a minimal TATA-box, with or without flanking chick beta-globin insulators. By using this model in combination with the IVIS imaging system, in vivo ER activation was measured. Dose- and time-dependent luciferase activity was induced in various organs of adult transgenic male mice exposed to diethylstilbestrol (DES) (10-1000 micro g/kg) and 17beta-estradiol dipropionate (EP) (10-1000 micro g/kg), when luciferase activity was measured ex vivo. The highest (>10 000-fold) induction of luciferase was measured in bone and kidney 24 h after exposure to 1000 micro g/kg EP. Other highly responsive organs include liver, testis, pituitary, brain, prostate and colon, which show different activity profiles. This in vivo model for detecting estrogenic activity can be used to assess tissue-specific action of ER agonists and antagonists. These could include selective ER modulators and environmental estrogens. In combination with the IVIS imaging system, this in vivo model is a powerful tool for assessing the kinetics of gene activation by estrogenic compounds.