Te. Spencer et al., NEONATAL AGE AND PERIOD OF ESTROGEN EXPOSURE AFFECT PORCINE UTERINE GROWTH, MORPHOGENESIS, AND PROTEIN-SYNTHESIS, Biology of reproduction, 48(4), 1993, pp. 741-751
To determine whether neonatal age and estrogen exposure affect uterine
growth, morphogenesis, and protein synthesis, crossbred gilts were ra
ndomly assigned at birth (Day 0) to receive cipher com oil vehicle (CO
) or estradiol-17beta valerate (EV; 50 mug/kg BW/day). Gilts were trea
ted for 7 days, chosen to coincide with specific periods of uterine de
velopment, prior to hysterectomy on Day 7, 14, or 49. Uteri were weigh
ed, and tissues were fixed for histology or explanted with L-4,5-[H-3]
leucine (H-3-leu) for 24 h. Endometrial and myometrial thicknesses wer
e measured in uterine wall cross sections. Radiolabeled proteins produ
ced by uterine wall tissues from H-3-leu and released into explant med
ium were identified by fluorography of two-dimensional SDS-PAGE gels.
Proteins for which fluorographic spot intensities were consistently af
fected by age and/or treatment were excised from gels, and associated
radioactivity was quantified. Normal growth and histogenesis were obse
rved in uteri from CO-treated gilts. Exposure to EV increased (p < 0.0
1) uterine wet weight on all days examined, although effects were most
pronounced on Day 49 (day X treatment, p < 0.01). Histologically, ute
ri of EV-treated gilts exhibited precocious or altered patterns of dev
elopment of endometrial glands and folds. Endometrial thickness was gr
eater (p < 0.01) in EV-treated gilts, and response was most pronounced
on Day 49 (day x treatment, p < 0.01). Treatment with EV increased (p
< 0.01) myometrial thickness on Day 49 only. Twenty-five uterine prot
eins were identified to be affected consistently by neonatal age, EV,
or both. Production of four of these proteins was affected by age alon
e, while six were affected exclusively by treatment with EV alone, and
15 were affected differentially by both age and EV. Treatment with EV
affected production of three of these 25 proteins on Day 7, 8 of 25 o
n Day 14, and 14 of 25 on Day 49. Results indicate that uterine growth
and development of the porcine uterine wall during early neonatal lif
e are accompanied by predictable alterations in patterns of uterine pr
otein synthesis. Data also demonstrate that the neonatal porcine uteru
s is estrogen-sensitive and that both physical and biochemical respons
es of uterine tissues to estrogen vary with period of exposure. It is
suggested that EV may be useful as a tool with which to induce develop
mental lesions in neonatal porcine uterine tissues. Identification of
EV-induced lesions in adult uterine tissues and of the neonatal period
s associated with their induction will represent an important step tow
ard identification of developmental determinants of porcine uterine ca
pacity.