OVARY-INDEPENDENT ESTROGEN-RECEPTOR EXPRESSION IN NEONATAL PORCINE ENDOMETRIUM

Effects of age and ovariectomy (OVX) at birth on uterine growth, endom etrial development, and estrogen receptor (ER) expression were determi ned for intact and OVX gilts (n = 5 per day) hysterectomized on postna tal days (PND) 0, 15, 30, 60, 90, or 120. Uteri were evaluated histolo gically, and ER protein and mRNA expression were characterized immunoh istochemically and by in situ hybridization. OVX did not affect uterin e weight or endometrial thickness until after PND 60, when both increa sed more rapidly in intact gilts. Neither did it affect genesis of ute rine glands, which were present and which proliferated after PND 0, or endometrial ER expression patterns in glandular epithelium (CE), lumi nal epithelium (LE), or stroma (S) between PND 0 and 120. Endometrium was ER negative at birth. On PND 15, the ER signal was strong in GE, w eak in S, and effectively absent in LE. Thereafter, although the ER si gnal remained strong in GE and increased through PND 60 in S, it was n ot evident consistently until after PND 30 in LE. The data indicate th at 1) porcine uterine growth and endometrial morphogenesis are ovary-i ndependent processes before PND 60; 2) uterine gland genesis is associ ated temporally with development of ER-positive endometrial GE and S; and 3) regulation of endometrial ER expression is ovary independent be tween PND 0 and 120. The results establish the ER as a marker of GE di fferentiation and implicate this receptor in mechanisms regulating end ometrial morphogenesis in the neonatal pig.