Effects of oral administration of tamoxifen, toremifene, dehydroepiandrosterone, and vorozole on uterine histomorphology in the rat

Tamoxifen, toremifene, DHEA, and vorozole inhibit tumor growth in rodent ma mmary carcinoma models and are promising chemotherapeutic agents for use ag ainst breast cancer development. In the present study, the effect of these agents on uterine histomorphology following oral administration to mature o vary-intact rats (n = 380) was examined. Animals received diet only (contro l), tamoxifen (0.4 and 1 mg/kg of diet; 10 mg/kg BW by daily gavage), torem ifene (3-30 mg/kg of diet), DHEA (24-2000 mg/kg of diet), or vorozole (0.08 -1.25 mg/kg BW by daily gavage) for 28 days and were either sacrificed or r eturned to a basal diet and then sacrificed 21 days later. Treatment with t oremifene (all doses) or tamoxifen (1 and 10 mg/kg) for 28 days produced a decrease (P < 0.05) in overall uterine size and myometrial thickness; howev er, uterine luminal and glandular epithelia cell height increased (P < 0.05 ) compared with control. These compartmentalized uterotrophic and antiestro genic effects of toremifene and tamoxifen were still apparent after 21 days post-treatment. Administration of DHEA (2000 mg/kg of diet) for 28 days ha d dramatic uterotrophic effects, increasing (P < 0.05) overall uterine size and stimulating all three uterine compartments (epithelia, stroma, and myo metrium), The other doses of DHEA, however, were not uterotrophic, Interest ingly, after removal of DHEA from the diet, uterine weight and myometrial t hickness decreased (P < 0.05), Vorozole (1.25 mg/kg) administration for 28 days had differential, compartmentalized uterine effects, producing an incr ease (P < 0.05) in epithelial cell height, a decrease(P < 0.05) in stromal size, but no change in myometrial thickness. After 21 days postadministrati on of vorozole, luminal epithelial cell height was increased (P < 0.05) com pared with control. The data suggest that oral administration of tamoxifen, toremifene, DHEA, and vorozole results in differential, compartmentalized effects in the uterus that are highly dependent on treatment dose. The data may have implications for risk assessment of these agents prior to adminis tration to healthy, cancer-free women.