Use of chromatofocusing to distinguish estradiol receptor from ovarian-dependent and -independent rat mammary tumors.
Cytosol estradiol receptor from MTW9-D (ovarian dependent) and MTW9-MtT (ovarian independent) rat mammary tumors were fractionated by chromatofocusing, a procedure which separates proteins on an ion-exchange column as a function of isoelectric point. Receptor from MTW9-D usually fractionated as three peaks with mean pH at peak height of 7.5, 6.8, and 6.0. The intermediate peak at pH 6.8 was present in 90% of MTW9-D tumors examined but in only 20% of MTW9-MtT tumors. Treatment of cytosols with 20 mM sodium molybdate or 50 mM leupeptin did not change the chromatofocusing profiles. The pI 6.8 fraction of receptor bound quantitatively to DNA-cellulose after ammonium sulfate precipitation, while receptor in the other two peaks bound much less. The quantitative binding of a fraction of estradiol receptor characteristic of MTW9-D to DNA is consistent with the greater binding of unfractionated cytosol receptor from MTW9-D to DNA than the binding of receptor from MTW9-MtT. Sucrose gradient analysis of the pI 6.8 receptor showed a sedimentation coefficient slightly less than ovalbumin with a Stokes radius of 26 A as determined by agarose chromatography. The correlation of receptor binding to DNA with response to ovariectomy might make this form of receptor a potential marker of hormonal responsivity in mammary tumors.
D000818:Animals; D002460:Cell Line; D002852:Chromatography, Ion Exchange / Q000379:methods; D003600:Cytosol / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D006863:Hydrogen-Ion Concentration; D008325:Mammary Neoplasms, Experimental / Q000378:metabolism*; D010053:Ovary / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D011959:Receptors, Estradiol; D011960:Receptors, Estrogen / Q000302:isolation & purification* / Q000378:metabolism
D011959:Receptors, Estradiol; D011960:Receptors, Estrogen; D004958:Estradiol