Biochemical and Immunohistochemical Analyses of Estrogen and Progesterone Receptors in the Rhesus Monkey Uterus During the Proliferative and Secretory Phases of Artificial Menstrual Cycles

On day 9 of an artificial menstrual cycle (28 day) in the rhesus monkey, endometrial epithelia and stroma and myometrial smooth muscle cells showed positive immunoreactivity for estradiol (E2) and progesterone (P) receptor. On day 23 a reduction of staining for E2 and P receptor was observed for epithelial cells in endometrial zones I, II, and III with a pronounced loss of E2 receptor staining in stromal cells. Glandular epithelial cells in zone IV retained strong positive staining for both E2 and P receptor. Cytosolic and occupied nuclear E2 receptor analyzed biochemically were significantly reduced on day 23. These data suggest that P induces a zonal-dependent distribution of immunoreactive E2 and P receptor and that epithelial cells of zone IV are distinguished by the combined presence of strong immunoreactive staining for both receptors.