Induction of Uterine Ornithine Decarboxylase (ODC) by Antiestrogens. Inhibition of Estradiol-Mediated Induction of ODC: A Possible Mechanism of Action of Antiestrogens

Abstract

The ability of antiestrogens (tamoxifen and nafoxidine) to affect uterine ornithine decarboxylase (ODC) in the ovariectom-ized rat was determined. Tamoxifen citrate (1 mg or 10 mg/kg) and nafoxidine (0.5 mg/kg) markedly elevated ODC levels. Tamoxifen (1 mg/kg) given for 4 days totally inhibited the E₂ (0.5 μg/kg)-mediated induction of ODC. Similarly nafoxidine (0.5 mg/kg) given once a day for 2 days inhibited the E₂-mediated induction of ODC. The relation of the inhibition of ODC induction by antiestrogens to their mechanism of action as anti-estrogens is discussed.