[3H]DU41165: a high affinity ligand and novel photoaffinity labeling reagent for the progesterone receptor.
17 alpha-Acetoxy-6-fluoro-16-methylene-(9 beta, 10 alpha)pregna-4,6-dien- 3,20-dione (DU41165), a retroprogestin (9 beta, 10 alpha) embodying a fluorine-substituted dienone system, has been prepared in high specific activity tritium-labeled form (4 Ci/mmol) and shown to be a high affinity ligand for the progesterone receptor (PgR) and a highly selective photoaffinity labeling reagent for PgR. The radiosynthesis involved conversion of DU41231 (the 17 alpha-hydroxy analog of DU41165) to DU41165 by treatment with tritium-labeled acetic anhydride. The binding affinity of DU41165 for PgR was determined by both a competitive binding assay and a direct binding assay (Scatchard analysis) to be 1.6-2.2-times higher than that of the high affinity synthetic progestin promegestone (R5020). In unlabeled form, DU41165 demonstrates photoinactivation of PgR to the extent of 60% at 60 min. In radiolabeled form [3H]DU41165 demonstrates specific covalent attachment with an efficiency of 5-7%. SDS-polyacrylamide gel electrophoresis of photoattached [3H]DU41165 confirms that there is covalent labeling of both the B subunit (Mr = 118,000), and the A subunit (Mr = 88,000) of PgR in a molar ratio of approximately 1:3.
Pinney
K G
KG
Department of Chemistry, University of Illinois, Urbana 61801.
Carlson
K E
KE
Katzenellenbogen
J A
JA
D000345:Affinity Labels; D001667:Binding, Competitive; D055598:Chemical Phenomena; D002621:Chemistry; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D010777:Photochemistry; D011282:Pregnenediones; D045167:Progesterone Congeners; D011869:Radioligand Assay; D011980:Receptors, Progesterone / Q000032:analysis*
D000345:Affinity Labels; D011282:Pregnenediones; D045167:Progesterone Congeners; D011980:Receptors, Progesterone; C012151:DU 41165