I have worked with this subject for several years now.
Of course that you can collect vaginal smears from the animal, and check on the estrogenic levels.
I have studied the effects of ageing on the WISTAR RAT uterus, from the perspective of the vascular networks, since childhood, through sexual maturity, in pregnancy, and old-age .These links might interest you.
and hello from Indonesia Maria ^_^, you said that the research conducted in wistar rats, can it related to other species e.g. guinea-pig? thanks again :)