Local placental influence on the uterine concentration of oestradiol-17 beta and progesterone in the pregnant guinea-pig.

Oestradiol-17 beta (Oe2) and progesterone (P) concentration in the various regions of the uterus, and in ovaries with or without corpora lutea, were determined in the unilaterally pregnant guinea-pig at mid-term and full-term of pregnancy. The concentrations of both Oe2 and P were highest in the non-pregnant horn, and lowest in the perifoetal and juxtaplacental tissue in mid-term and term pregnancies, respectively. The Oe2 concentration in corpus luteum bearing ovaries was much lower than in those without corpora lutea, whereas the P concentration was higher. Ovariectomy performed at term resulted in a decrease of about 40% in plasma P concentration and no significant change in Oe2 concentration. This suggests that there is at least some contribution of P by the ovary even at term of pregnancy. The present data also provide strong evidence for the lack of local placental influence on the concentration of Oe2 and P in the uterus.