Uterine Space Affects Placental Protein Secretion in Swine1

The effect of altering uterine space available to developing conceptuses on placental and endometrial protein secretion and endometrial 3H-thymidine incorporation on Days 25 and 35 of gestation was tested. Gilts bred at estrus (Day 0) were laparotomized on Day 4, and the uterine horn ipsilateral to the ovary with the most ovulations was ligated midway between the uterine tip and uterine bifurcation to create a crowded and a roomy uterine environment. On Day 25 (n = 7) or 35 (n = 6), gilts were killed and the reproductive tract was dissected from each. Each placenta and fetus was weighed, and a sample of endometrium adjacent to each placenta was collected. Within each uterine environment, tissues (500 mg) from the heaviest and lightest (by weight) placentae and adjacent endometrial tissue were cultured for 24 h at 37 degrees C in 15 ml Minimal Essential Medium having 0.1 times the normal amount of leucine plus 50 microCi 3H-leucine. Aliquots (2 ml) of dialyzed medium were subjected to two-dimensional PAGE and fluorography to examine proteins with molecular weight ranges of approximately M(r) 20,000-130,000, and a further aliquot was subjected to SDS-PAGE to examine low molecular weight proteins (M(r) 2000-20,000). In addition, endometrium (200 mg in duplicate) adjacent to the heaviest and lightest placentae within each uterine environment was incubated for 4 h in 5 ml MEM plus 1 microCi 3H-thymidine to measure DNA synthesis. After culture, 3H-thymidine incorporation and total DNA were determined. Fetal survival in the crowded uterine environment decreased (p < 0.05) on Day 35 compared to Day 25. On both days, the heaviest and lightest placentae from the crowded uterine environment weighed less (p < 0.01) than the heaviest and lightest placentae from the roomy uterine environment. The fetuses associated with the heaviest and lightest placentae from the crowded uterine environment also weighed less (p < 0.05) than fetuses associated with the heaviest and lightest placentae from the roomy uterine environment. Nondialyzable radioactivity in medium per gram of tissue cultured from placental cultures decreased (p < 0.05) and from endometrial culture increased (p < 0.05) between Days 25 and 35. Placental secretion of a protein with M(r) 46,000, pI 5, decreased between Days 25 and 35. Endometrial secretion of three proteins (M(r) 35,000, pI 6.2; M(r) 25,000, pI 4.9; and M(r) 14,000, pI unknown) increased, and secretion of three other proteins (M(r) 24,000, pI 6.5 doublet; M(r) 22,000, pI 7.5, and M(r) 7000, pI unknown) decreased from Day 25 to Day 35 of pregnancy.(ABSTRACT TRUNCATED AT 400 WORDS)