Nuclear binding of estradiol in human myometrium

Abstract

The nuclear uptake of human myometrial estrogen receptors in cytosol prepared in a low salt medium in the presence and absence of diisopropylfluorophosphate (DFP) has been studied. The [ 3H]-estradiol receptor complex in the cytosol prepared in the presence of DTP showed a much greater nuclear binding activity than the receptor complex in the cytosol prepared in the absence of DFP. This difference in the nuclear translocation was obtained in spite of the greater binding capacity of the receptors in cytosol prepared in the absence of DFP. Receptors prepared in the presence of DFP seclimented at 9.0 S, 5.3 S and 4.2 S. Sucrose density gradient centrifugation of the cytoplasmic receptors after incubation with nuclei showed that radioactivity seclimenting at 9.0 S disappeared and no significant changes in the 5.3 S and 4.2 S areas was observed. Nuclear uptake of [ 3H]-estradiol receptor complex from cytosol prepared in the absence of DFP was also dependent on the presence of the 9.0 S receptor complex while the 4.2 S proteolytic fragment did not show any nuclear binding activity. A correlation coefficient of 0.99 was obtained when the decrease in the amount of 9.0 S receptor form was plotted against the amount of [ 3H]-estradiol extracted from the nuclear pellet.