title: 3H-labelled RU 38486: characterization of binding sites in human uterine cytosol.
abstract: The behaviour of the antifertilizing synthetic steroid RU 38486 towards human uterine progestin receptor was investigated. RU 38486 competed in the same order of magnitude as progesterone for the [3H]R 5020 binding site of progestin receptor, whereas R 5020 was unable to compete against [3H]RU 38486. This apparent contradiction could be explained by means of HPLC-chromatography. HPLC-chromatography with an anion exchange column (MonoQ, Pharmacia, Uppsala, Sweden) showed that [3H]RU 38486 forms at least two stable complexes with uterine cytosol, on one hand with serum albumin, which presents almost 90% of bound radioactivity, and on the other hand with the two native progestin receptor forms, corresponding to 4 S and 8 S receptor forms in sucrose density gradient analysis. Whether reduced binding of salt-activated RU 38486 receptor complexes to DNA-cellulose is due to reduced activation is still uncertain and remains to be further investigated.
mesh_terms: D000019:Abortifacient Agents / Q000378:metabolism*; D000021:Abortifacient Agents, Steroidal / Q000378:metabolism*; D001665:Binding Sites; D002499:Centrifugation, Density Gradient; D002851:Chromatography, High Pressure Liquid; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004963:Estrenes / Q000378:metabolism*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D015735:Mifepristone; D011506:Proteins / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism; D013696:Temperature; D013997:Time Factors; D014599:Uterus / Q000378:metabolism*
chemical_list: D000019:Abortifacient Agents; D000021:Abortifacient Agents, Steroidal; D004963:Estrenes; D011506:Proteins; D011980:Receptors, Progesterone; D015735:Mifepristone; D004247:DNA