A Cytoplasmic Progesterone Receptor in Hen Pituitary and Hypothalamic Tissues

Abstract

The cytosol fraction of the anterior lobe of the pituitary in laying White Leghorn hens was shown to possess a progesterone-binding component which preferentially bound progesterone. A similar component was also found in the cytosol of the hypothalamus and of the oviduct magnum. The (Kd) at equilibrium was determined as 1.68 .+-. 0.10 (SE) .times. 10-10 M in the pituitary, 3.29 .+-. 0.10 .times. 10-10 M in the hypothalamus, and 3.02 .+-. 0.40 .times. 10-10 M in the oviduct magnum, whereas the number of binding sites/mg cytosol protein was 5.99 .+-. 0.084 (SE) .times. 10-13 mol in the pituitary, 0.43 .+-. 0.003 .times. 10-13 mol in the hypothalamus, and 2.88 .+-. 0.114 .times. 10-13 mol in the oviduct magnum. The results suggest that a cytoplasmic progesterone receptor is present in the pituitary and hypothalamic tissue, as well as in the oviduct magnum, of the hen.