Immunolocalization of oestrogen and progesterone receptors in the human decidua in relation to prolactin production.

The distribution of oestrogen and progesterone receptors within the decidualized stroma of the uterus was examined in early and term human pregnancy and the results related to the effect of oestradiol and progesterone on prolactin production by decidua in vitro. In early pregnancy progesterone receptors were present in the nucleus of decidualized cells of both the capsularis and parietalis but not in glandular cells. In contrast at term progesterone receptors were located within the cytoplasm of decidual cells. Oestrogen receptors were detected only in the nucleus and were present in greater amounts in decidua capsularis than parietalis in early pregnancy, but were not detectable in term decidua. Both oestrogen and progesterone receptors were present in the nuclei of cells of arterioles within the decidua. In early pregnancy prolactin production decreased during in-vitro culture of decidua parietalis but was maintained in decidua capsularis, associated with an increase in progesterone production by the decidua capsularis. In term decidua, prolactin production in vitro was only stimulated by a combination of oestradiol and progesterone. These results suggest, firstly, that maintained decidualization and prolactin production by decidua capsularis during treatment of women in early pregnancy with the anti-progestin mifepristone is not due to an absence of progesterone receptor; secondly, there is a shift in immunoreactive progesterone receptor in decidual cells from the nucleus in early pregnancy to the cytoplasm in term pregnancy. This may indicate an alteration in the action of progesterone around the time of parturition; and thirdly, in term decidua, progesterone, apparently acting through the cytoplasmic receptor, is active in increasing prolactin production in vitro only when combined with oestradiol.