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 oxy tocin (OTR) in the marmoset uterus have been analysed throughout the entire cycle and early pregnancy, Uteri obtained during the early, mid/late and l ate proliferative phase, and the early, mid and late secretory phase and ea rly pregnancy were examined by immunohistochemistry (OTR, ER, PR) and autor adiography (OTR), A massive upregulation of the ER in the cell nuclei of gl andular epithelium and stromal cells during the mid proliferative phase was succeeded by a declining staining intensity and positively stained cell nu mber in the secretory phase. PR immunoreactivity increased in the late prol iferative phase and early secretory phase, mainly within the cell nuclei, a nd then declined in both intensity and cell number towards the mid to late secretory phase. Myometrium showed a similar staining pattern for the stero id receptors, OTR were expressed weakly in stroma throughout the entire cyc le, increasing slightly in the secretory phase. Glandular epithelium showed positive staining only during the periovulatory period. Myometrial OTR exp ression was weak during the proliferative phase, increased towards the secr etory phase, and was maximal in the late secretory phase, Myometrial tissue adjacent to endometrium was most strongly stained, A cyclic shift evidentl y occurred in the pattern of steroid receptors, perhaps reflecting the ster oid environment or the luteinizing hormone increase associated with ovulati on.