[Interaction of androgens with uterine receptors]

Interactions of testosterone and 5 alpha dihydrotestosterone with the estrogen receptor have been studied in the immature rat uterus. At low concentrations, androgens interact with their own receptors (1) which are different from the estrogen receptor by their specificity, sedimentation constant and number of binding sites (2) (Table I). At high concentrations, androgens interact with the estrogen receptors, as shown by "rate" competitive experiments performed on uterine cytosol. This low affinity interaction is efficient to translocate the estrogen receptor to the nucleus in vitro (3) and in vivo (fig. I). Androgens also bind to the progesterone receptor. The responsibility of these interactions in the observed uterotrophic and anti estrogenic effect of androgens will be discussed.