Endogenous production of ovarian estradiol-17 beta and its plasms levels in young rats.

Estradiol-17 beta concentration in the plasma and its production in ovaries of Wistar rats have been assayed from infancy until puberty (i.e. from the 5th till 39th days of postnatal life). The highestest estradiol-17 beta plasma concentration was found between the 15th and 20the postnatal day. 24 hrs before the vagina opened plasma estradiol-17 beta rapidly rose. Estradiol-17 beta reproduction between days 15 and 33 remained at a stable level, but its production was highest at 39 days. The increase in estradiol-17 beta production and its plasma concentration on the 35th postnatal day until the immediate onset of puberty points to a maturation process occurring at a certain period in the development of sex function in which estrogens plays a dominant role.