Expression of the oxytocin receptor in relation to steroid receptors in the uterus of a primate model, the marmoset monkey.

The dynamics of the receptors for oestrogen (ER), progesterone (PR) and oxytocin (OTR) in the marmoset uterus have been analysed throughout the entire cycle and early pregnancy. Uteri obtained during the early, mid/late and late proliferative phase, and the early, mid and late secretory phase and early pregnancy were examined by immunohistochemistry (OTR, ER, PR) and autoradiography (OTR). A massive upregulation of the ER in the cell nuclei of glandular epithelium and stromal cells during the mid proliferative phase was succeeded by a declining staining intensity and positively stained cell number in the secretory phase. PR immunoreactivity increased in the late proliferative phase and early secretory phase, mainly within the cell nuclei, and then declined in both intensity and cell number towards the mid to late secretory phase. Myometrium showed a similar staining pattern for the steroid receptors. OTR were expressed weakly in stroma throughout the entire cycle, increasing slightly in the secretory phase. Glandular epithelium showed positive staining only during the periovulatory period. Myometrial OTR expression was weak during the proliferative phase, increased towards the secretory phase, and was maximal in the late secretory phase. Myometrial tissue adjacent to endometrium was most strongly stained. A cyclic shift evidently occurred in the pattern of steroid receptors, perhaps reflecting the steroid environment or the luteinizing hormone increase associated with ovulation.