| Sumario: | The number of androgen (AR) and estrogen receptor (ER) binding sites was quantitated in cytosol fractions from adult intact male and female rats. The apparent equilibrium constants of dissociation were: 0.8 × 10−9 M for the AR measured with [3H]-R 1881 and 0.6 × 10−9 M for the ER labelled with [3H]-estradiol. The mean (±SD) number of available binding sites were (fmol/mg cytosol protein): male: AR: 88.6 ± 7.7 ER: 8.5 ± 1.4; female: AR: 23.8 ± 1.6 and ER: 7.6 ± 0.5. Orchidectomy Caused a two-fold increase in the number of available androgen and estrogen binding sites with a clear-cut reduction 10 days after castration. Ovariectomy elicited an unexpected decrease of ER one day after gonadectomy and full recovery of binding sites was found at 10 days. A significant increase in AR was seen 4 days following ovariectomy. © 1980, All rights reserved.
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