Bj. Tarleton et al., OVARY-INDEPENDENT ESTROGEN-RECEPTOR EXPRESSION IN NEONATAL PORCINE ENDOMETRIUM, Biology of reproduction, 58(4), 1998, pp. 1009-1019
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.