The Present study hart been carried out to elucidate the antiestrogenic effects of tamoxifen in uteri of immature rats.
Immature female Sprague-Dawley rats were allocated: into 4, groups. and injected with 5㎍ of estradiol-17β, 50㎍ of tamoxifen, a combination of both or vehicle only subcutaneously three times after an interval of 24 hours respectively, The concentrations, of cytosol estradiol receptor in uterus were measured by DCC method before and 1, 3, 6, 12, 24, 48 and 72 hours after the above treatments and those of nuclear estradiol were measured by protamine exchange method 72 hours and those of nuclear estradiol were measured by protamine exchange method 72 hours after the above treatments.
The results obtained were summarized as follows :
1. The binding affinity of tamoxifen to estradiol receptor in uterine cytosol was lower than that of estradiol-17β, accordingly the translocation of estradiol receptor into the nucleus was found to be delayed.
2. Tamoxifen caused the retention of estradiol receptor in nucleus over 24 hours and inhibited the replenishment of the receptor from nucleus to cytosol in uterus.
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