Nuclear Localization of Progesterone Receptor before and after Exposure to Progestin at Low and High Temperatures: Autoradiographic and Immunohistochemical Studies of Chick Oviduct*

Publisher Website
Google Scholar
Abstract
The intracellular location of progesterone receptor and tritiated progestin was assessed in chick oviduct before and after in vitro exposure to 5 nM [3H]Org 2058 ([6,7-3H]16.alpha.-ethyl-21-hydroxy-19-nor-4-pregnene-3,20-dione) for 5 or 45 min at 4 or 37 C. The experiments were designed to allow the intracellular localization of occupied and unoccupied receptor in relatively intact tissue. Autoradiography and immunohistochemistry were used to localize [3H]Org 2058 and the progesterone receptor, respectively. Autoradiograms showed radiolabeled progestin concentrated in oviduct cell nuclei not only after incubation at 37 C, but after incubation at 4 C as well. Cytoplasmic concentration was never observed. Immunostaining revealed progesterone receptor always located in cell nuclei, regardless of temperature or time of exposure to labeled ligand or whether the tissue was exposed to progestin. The results indicate that the chick oviduct nuclear progesterone receptor does not undergo a temperature-dependent translocation from cytoplasm to nucleus upon binding ligand.