Short term treatment of tamoxifen and estradiol on estradiol and progesterone receptors in rabbit uterus.

ABSTRACT

Effects of tamoxifen (Tam) on cytosolic estradiol (E2) receptors (ERc), progesterone (P4) receptors (PRc), nuclear estradiol (ERn) and progesterone receptors (PRn) were studied in adult normal rabbit uterine tissue. The ratio of cytosol nuclear estradiol receptors (ER) was greater in rabbits treated with Tam than E2 or control uterine tissues. Rabbit uterine progesterone receptors (PR) in E2 treated animal were greater than Tam-treated animals. Tam caused nuclear accumulation of estradiol receptor, and simultaneous administration of E2 + Tam 500, estradiol could not revert Tam mediated accumulation of ER. The results suggest that Tam has an essentially antagonist action in the rabbit uterine tissue.