Effects of antiestrogenic compounds on avian medullary bone formation

Administration of estradiol to male Japanese quail induced the formation of medullary bone in the marrow cavities of the bird's femora and tibiae. This was accompanied by increased serum levels of calcium, phosphorus, and alkaline phosphatase activity. We examined the effects of two structurally distinct "antiestrogens" on the estrogen-induced formation of medullary bone in this quail model. Trioxifene (LY133314) and tamoxifen are members of a group of compounds commonly referred to as antiestrogens that elicit mixed agonist-antagonist actions on estrogen target tissues. In our experiments, these compounds did not display estrogen agonist properties with respect to medullary bone formation. They also did not elicit changes in serum calcium, phosphorus, or alkaline phosphatase activity. When given concurrently with estradiol, the compounds inhibited both the estrogen-induced formation of medullary bone and the associated changes in serum parameters. Trioxifene appears to be somewhat more potent than tamoxifen in antagonizing estrogen effects in this model.