Abstract
Vaginal smears were studied from spayed mice that received estriol daily for 4 days. Blocker, testosterone propionate, progesterone or desoxycorticosterone acetate was injected on 1 of the 4 days. Testosterone was an effective antagonist when injected early in the test period, days 1 or 2, with lesser effect on day 3 and none on 4. Desoxycorticosterone was inhibitory only when given on days 3 or 4. Progesterone produced highly significant block when administered on days 2 or 3, statistically significant, but less marked block on day 4, and none on day 1. These temporal relationships are remarkably similar to those obtained with estrone-treated mice; differences appear to be quantitative, rather than qualitative. Thus estrone and estriol appear to associate with the same activating site in the mouse vagina, in contrast to the mouse uterus in which a 2nd site need be invoked to explain the actions of estriol.
