PURIFICATION AND PARTIAL CHARACTERIZATION OF A 17-BETA-ESTRADIOL-BINDING MACROMOLECULE IN THE HUMAN-PANCREAS

  • 1 January 1982
    • journal article
    • research article
    • Vol. 42  (2) , 633-637
Abstract
The presence of estrogen-binding proteins in the human pancreas that may provide the biochemical basis for tissue-specific treatment of pancreatic carcinoma with estrogen-based cytotoxic drugs was investigated. Using in vitro techniques, an estrogen-binding macromolecule was purified from human pancreatic cytosol. With estradiol as ligand, Kd was calculated to be 1.7 .times. 10-7 M, and this protein constituted about 4% of the total protein content in the cytosol. No metabolism of estradiol was detected under the in vitro conditions used. Competition experiments indicated that, besides estradiol, the protein also had some affinity for estrone and estriol but not for testosterone, progesterone or dexamethasone. The protein was purified to homogeneity using chromatography on concanavalin A and hydroxylapatite followed by preparative polyacrylamide gel electrophoresis. The purified protein, still able to bind [3H]-estradiol, gave 1 single protein-staining band when analyzed using different electrophoretic systems. The steroid-protein complex did not bind to phosphocellulose or DNA-cellulose and did not show any similarities to steroid receptor proteins. The complex has a Stokes'' radius of 52 .ANG. and a sedimentation coefficient of 3S. The biological significance of the macromolecule is unknown but the protein is probably synthesized in the pancreas since no similar protein could be detected in serum. Studies are now being carried out to investigate whether this novel protein in the human pancreas may interact with complexes between cytotoxic agents and estrogens and provide the basis for tissue-specific treatment of pancreatic carcinoma.

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