The present study has been carried out to elucidate the antiestrogenic effects of tamoxifen on RNA and protein synthesis 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 with an interval of 24 hours respectively.
The specific activities of ³H-uridine incorporation into uterine RNA and those of ³H-leucine incorporation into uterine protein were measured before and 1,3,6,12,24,48 and 72 hours after the above treatments.
The results obtained were summarized as follows;
1. Tamoxifen itself increased RNA synthesis an hour after treatment(169.18% of control), but it´s specific activity was reduced to control level after 3 hours. Tamoxifen inhibited significantly (p<0.01) the activity of RNA synthesis of estradiol-17β.
2. The increasing rate of protein synthesis was lower in tamoxifen treated group than that in estradiol-17βtreated group. While the rate was steadily increased up to 357.4% of control by estradiol-17β in 72 hours, tamoxifen itself failed to increase the rate after 24 hours and significantly (p< 0.01) inhibited the activity of estradiol-17β(-167.4%).
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