Target Tissue Receptors for Progesterone: The Influence of Estrogen Treatment1

The effects of estrogen treatment on the specific progesterone binding protein (receptor) in the chick oviduct were investigated. The progesterone receptor is present in non-estrogen treated oviducts but the tissue concentration of this protein increases several fold during a 2- week-period of estrogen treatment. In addition, qualitative changes in the receptor protein are indicated by its sedimentation properties on sucrose gradients. Following estrogen treatment, the 4-5S progesterone-receptor complex is apparently altered to a form which sediments in the 6-8S region on sucrose gradients. These results suggest that the enhanced responsiveness of the oviduct to progesterone following estrogen treatment may arise through quantitative and qualitative changes in progesterone receptor molecules. (Endocrinology90: 1041, 1972)