title: [Estradiol receptors in the cytosol of nitrosomethylurea-induced mammary tumors of the rat. Influence of cell nuclei on the cytoplasmic estradiol receptor].
abstract: The cytoplasmic estradiol receptor (ERc) in N-nitrosomethylurea induced mammary tumors of the rat was described and its binding properties were characterized. We found an estradiol receptor incidence of 100% and an ERc content of 40 +/- 10 fmol/mg cytosol protein (n = 18) 3-4 days after ovariectomy. A dissociation constant (KD) of 2,2 +/- 1,1 X 10(-10) M was measured. The optimal incubation time for the determination of the ERc was found to be c.18 h (0-4 degrees C). The occupied ERc was relatively stable (we observed only a c. 20% degradation of the estradiol receptor after an incubation time of 66 h (0-4 degrees C) in comparison with the value found during an incubation time of 18 h (0-4 degrees C), the unoccupied ERC is more instable. We found an inactivation of ERc after freezing of tumor tissue in dry ice for longer times (in this paper for 18 d). The occupied estradiol receptor was stable for at least 30 min at 30 degrees C, if an excess of steroid is available in the assay system (in this paper 4 X 10(-9) M). A distinct degradation was observed if occupied cytosol was incubated at 37 degrees C. We found a fast inactivation of the ERc if cytosol and nuclei were incubated together at 30 degrees C. At temperatures of 0-4 degrees C (incubation of cytosol plus nuclei) a slight degradation of the ERc could be seen. This degradation was not significant in every case. Nuclei of N-nitrosomethylurea-induced mammary tumors of the rat possess apparently a "factor" which is able to inactivate the cytoplasmic estradiol receptor and is highly active at elevated temperatures. It is possible that this "factor" also acts at temperatures of 0-4 degrees C but with diminished activity.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000032:analysis* / Q000378:metabolism; D003593:Cytoplasm / Q000032:analysis; D003600:Cytosol / Q000032:analysis*; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000032:analysis* / Q000139:chemically induced; D000090204:Mesothelin; D008770:Methylnitrosourea; D011485:Protein Binding; D051381:Rats; D011919:Rats, Inbred Strains; D011959:Receptors, Estradiol; D011960:Receptors, Estrogen / Q000032:analysis* / Q000378:metabolism; D013696:Temperature
chemical_list: C000715529:Msln protein, rat; D011959:Receptors, Estradiol; D011960:Receptors, Estrogen; D004958:Estradiol; D008770:Methylnitrosourea; D000090204:Mesothelin
vernacular_title: Ostradiolrezeptoren im Zytosol Nitrosomethylharnstoff-induzierter Mammatumoren der Ratte. Einfluss von Zellkernen auf den zytoplasmatischen Ostradiolrezeptor.