title: Comparison of formation, activation, and nuclear translocation of receptor . estradiol (R . E2) complex at 0 degrees C and 37 degrees C in intact uterine cells.
abstract: The present study was undertaken to establish whether molecular events leading to binding, transformation-activation, and nuclear translocation of cytoplasmic uterine estrogen receptor described for cell-free systems also occur in intact uterine cells. Cell suspensions were incubated at 0 degrees C or 37 degrees C with estradiol (E2) and specific binding to intracellular receptors was measured. The data demonstrate that saturation of specific estrogen binding sites occurs within 60 min at 37 degrees C and within 22 h at 0 degrees C, with a total of approximately 24,000 to 30,000 receptor sites per cell. At equilibrium, the total number and subcellular distribution of receptor . estradiol (R . E2) complexes formed in cells incubated at 0 degrees C or 37 degrees C were identical. Scatchard analysis of the equilibrium binding data yielded the same association constants for cytoplasmic and nuclear R . E2 formed in intact cells incubated at either temperature. Sucrose density gradient analysis of nuclear and cytoplasmic R . E2 formed in intact cells at 0 degrees C or 37 degrees C showed that at both temperatures, the nuclear R . E2 had a 5 S sedimentation coefficient; at both temperatures, a 5 S cytosol R . E2 was detected; only in the 0 degrees C incubation, an additional 4 S cytosol R . E2 was found. These results suggest that the molecular interactions regulating the dynamics of estrogen binding in the intact cell are similar at both physiological and low temperatures.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D007700:Kinetics; D051381:Rats; D011960:Receptors, Estrogen / Q000378:metabolism*; D013696:Temperature; D014599:Uterus / Q000378:metabolism*
chemical_list: D011960:Receptors, Estrogen; D004958:Estradiol