A possible non transcriptional effect of progesterone

Morphological and immunohistochemical differentiation patterns of rabbit uterine epithelium in vitro

We describe morphological and immunohistochemical changes of uterine epithelium from immature rabbits in vitro in response to hormonal treatments, using a matrix-coated semipermeable filter. These investigations were compared to in vivo studies of uterine epithelium from immature rabbits treated with estrogen and/or progesterone. In vitro, polarization of the epithelium seems to be best developed under progesterone dominance, and the pattern of cell organelles is similar to those seen in vivo. Two types of apical protrusions could be observed in cultures treated with progesterone, some shaped like domes, containing cell organelles, and some irregular in shape with small lucent vesicles. Both types of apical differentiation are typical for the in vivo situation. In vitro, estrogen leads to a more pseudostratified growth pattern of the cells. They develop apical protrusions with big vesicles probably containing mucin, as in vivo. Treatment with both steroid hormones leads to a heterogeneous response of the uterine epithelial cells in culture, some cells responding more to the estrogen, others to the progesterone whereas in vivo the progesterone-dominant features are obvious. Immunohistochemistry of uteroglobin in monensin-treated cultures gives evidence for uteroglobin secretion in all cultures, but to a lesser extent in the untreated, and this is strongly increased in cultures treated with estrogen and progesterone. These results correspond to observations made in vivo. This in vitro cell culture method seems therefore to provide a useful model for investigating the regulatory mechanisms of sexual steroid hormones and the cell biology of uterine receptivity.

Estradiol-17 beta and progesterone regulate secretion of uteroglobin through different pathways

Uteroglobin, the primary secretory protein of rabbit uterine epithelium, was localized by the direct immunoperoxidase method in uteri of control ovariectomized rabbits and of ovariectomized rabbits injected with progesterone or estradiol-17 beta. In control rabbits, staining for uteroglobin was almost entirely abolished six weeks after bilateral ovariectomy. Two days following progesterone injection of ovariectomized rabbits, intense staining for uteroglobin could be detected within the endoplasmic reticulum, Golgi complexes, and compact secretory vesicles of most endometrial epithelial cells. Estradiol-17 beta injection resulted in a different intracellular pattern of uteroglobin distribution. Two days following treatment with that steroid hormone, intense staining for uteroglobin was localized within large apical mucous droplets and moderate staining was present in the endoplasmic reticulum and Golgi complexes of these cells. The increased mucin content of the endometrial epithelium following treatment with estradiol-17 beta was confirmed by a periodic acid-Schiff histochemical reaction in the presence of diastase. Quantitation by radioimmunoassay of uteroglobin production in vitro by uterine fragment confirmed that progesterone had a greater effect on enhancing uteroglobin production than estradiol-17 beta and that both steroid hormones did not have any effect after 30 min of incubation in vitro. We suggest that progesterone not only regulates uteroglobin production at the transcriptional level, but that it also regulates the mode of uteroglobin secretion by the induction of a different pathway, compared with the one used when estradiol-17 beta is administered alone.

Uteroglobin: a model for the sutyd of progesterone action in mammals

Uteroglobin, a progesterone-binding protein, is expressed in several organs, principally endometrium and lung, of the rabbit and other rodents. The phasic activation of the uteroglobin gene in the endometrium during early pregnancy is regulated by progesterone, which contrasts with the constitutive, nonregulated expression of this gene in the lung. Thus, uteroglobin provides a useful model for the study of differential gene regulation by hormones as well as for the study of steroid-protein interactions.