High-performance hydrophobic-interaction chromatography of steroid hormone receptors

The use of high-performance hydrophobic-interaction chromatography (HPHIC) on SynChropak 500 propyl columns has been evaluated for the first time in the analysis of estrogen receptors labeled with [125I]iodoestradiol-17 beta. These receptors were extracted from reproductive tissues with 500 mM phosphate buffer and applied to the stationary phase. Utilizing an inverse phosphate gradient (500 to 10 mM), elution resulted in rapidly excluded components in the void volume followed by a second radioactive peak at 400 mM phosphate. Both peaks appeared to contain specific estrogen-binding components in that steroid association was inhibited by diethylstilbestrol and free ligand was eluted with a different retention time. A great deal of [125I]iodoestradiol-17 beta was retained by the column. Inclusion of acetonitrile (20%) in the mobile phase resulted in the elution of [125I]iodoestradiol-receptor complexes at a different position from free ligand. Distribution of specific estrogen-binding components appeared to be tumor-dependent. These preliminary results indicate that HPHIC may be useful for isolating various isoforms of steroid hormone receptors so that detailed information regarding their intrinsic properties may be ascertained.