U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska
Date of this Version
1994
Abstract
The effect of the conceptus and of reduced uterine space on endometrial protein secretion was examined on Days 40, 60, and 80 of gestation in white crossbred gilts. Twenty-nine gilts were checked daily for estrus, and 15 were given 5 mg estradiol valerate daily from Days 11 to 15 (Day 0 = day of estrus) of the estrous cycle to induce pseudopregnancy. The remaining 14 pigs were mated during estrus. All pigs were laparotomized on Day 4, and one uterine horn was ligated to produce one crowded and one roomy uterine environment. Pigs were killed on Days 40, 60, and 80 of pregnancy or pseudopregnancy. The reproductive tracts were collected, and placental tissues from pregnant pigs and endometrial tissues from all pigs were cultured in the presence of 3H-leucine to evaluate protein secretion. Conditioned medium was dialyzed, measured for incorporation of radioactivity into nondialyzable macromolecules, and then subjected to two-dimensional (2D)-PAGE to determine the effect of uterine space and day of pregnancy or pseudopregnancy on overall protein secretion rate and secretion of specific proteins. Fetal survival, fetal weight, and placental weight were decreased (p < 0.01) in the crowded uterine environment compared to the roomy uterine environment. Incorporation of 3 H-leucine into nondialyzable macromolecules by endometrial tissue in culture was not affected by uterine space. Secretion of nondialyzable macromolecules by endometrium from pregnant pigs was not different from that by endometrium from pseudopregnant pigs on Day 40 but was greater (p < 0.01) on Days 60 and 80. Results of 2D-PAGE indicated that secretion of two endometrial proteins appeared to be increased (M, 13 000, pi 7 and M, 13 000, p 5.5), and secretion of one protein appeared to be decreased (M, 14 000, pi 6.2), in pregnant vs. pseudopregnant pig endometrial cultures. Decreasing uterine space did not affect incorporation of 3H-leucine by placental tissue in culture. Examination of 2D-PAGE fluorographs of proteins secreted by placental tissue indicated that uterine space had no consistent effect on the array of proteins observed. However, secretion of a protein of Mr 35 000, pi 4 increased by Day 60. Another protein (M, 45 000, pi 4) increased by Day 80. Two other proteins (M, 12 500, pi 4.6 and Mr 13 000, pi 4.8) increased in some placental cultures by Day 60 of pregnancy and were consistently present in cultures from Day 80 placenta. These data indicate that uterine space does not influence endometrial or placental protein secretion on Days 40-80 of pregnancy. Secretion of specific proteins was greater by endometrium from pregnant compared to pseudopregnant pigs as early as Day 40 of pregnancy, and total endometrial protein secretion (measured as incorporation of 3'H-leucine into nondialyzable macromolecules) was greater for pregnant compared to pseudopregnant pigs by Day 60 of pregnancy; these findings suggest the possibility that the conceptus can alter endometrial protein secretion. The increase in endometrial protein secretion coincides with changes in secretion of specific placental proteins. These proteins or other compounds secreted by the conceptus may stimulate endometrial protein secretion during pregnancy.
Comments
Published in BIOLOGY OF REPRODUCTION 51, 748-754 (1994).