Effects of Day of the Estrous Cycle or Pregnancy on Protein Secretion by Caprine Endometrial Tissues1

Abstract

Our objectives were to evaluate temporal changes in protein secretion by endometrial explant cultures obtained from cycling or pregnant caprine does during the period of maternal recognition of pregnancy. Equal amounts of radiolabeled proteins from explant cultures were separated by one- and two-dimensional PAGE and visualized by fluorography. No consistent difference in proteins with molecular masses greater than 30 kDa was apparent when electrophoretic patterns were compared. However, on Days 18 and 21 of pregnancy there was an increase in the number and intensity of proteins having molecular masses between 18 and 22 kDa (pI = 6.2-7.2) when compared with endometrial secretory proteins obtained from goats on Day 18 of the estrous cycle. Three proteins were also detected in culture supernatants from endometrial explants obtained on Days 18 and 21 of pregnancy but not on Day 18 of the estrous cycle. A basic (pI > 7.5) 14-kDa protein could sometimes be resolved into two (or more) isoelectric variants. A second 14-kDa protein (pI = 6.9) and a less prominent 15-kDa protein (pI = 6.0) were also produced in response to the conceptus. These proteins then decreased in intensity, returning to levels characteristic of those earlier in pregnancy, by Day 30 of gestation. These caprine uterine secretory proteins may be involved in the process of maternal recognition of pregnancy.

Galectin 15 (LGALS15): A Gene Uniquely Expressed in the Uteri of Sheep and Goats that Functions in Trophoblast Attachment1

“…the synthesis and secretion of an unidentified 15-kDa protein with a pI of ;6.0 from explant cultures in response to the conceptus [70]. Interestingly, development of in vitro-produced bovine blastocysts transferred into sheep uteri resulted in the presence of crystals in trophectoderm cells [71,72].…”

Characterization of a Polarized Porcine Uterine Epithelial Model System1

“…The radiolabeled proteins obtained from the polarized pUE filter cultures were separated by two-dimensional SDS-PAGE (2D-PAGE) with 12.5% polyacrylamide gels as described previously [19]. Equal amounts (200 000 dpm) of radiolabeled proteins were subjected to isoelectric focusing (IEF) in the first dimension.…”

Regulation of protein and prostaglandin secretion in polarized primary cultures of caprine uterine epithelial cells

“…This is especially true for the low molecular weight, acidic proteins (14-22 kDa; pI 4.6-4.8) and the 14 kDa basic (pI > 7.5) protein secreted by cUE cells in culture. The biochemical characteristics of these proteins are identical to a complex of proteins temporally secreted by caprine endometrial explants obtained during the critical period (Days 15-21) of pregnancy recognition (45). The ruminant conceptus relies heavily on uterine histotroph during the prolonged preimplantation period (2,5).…”

“…Cell culture supernatants were harvested after 24 h, placed into ultrafiltration units (5000 MW cutoff), and centrifuged at 14 500 RCF to remove unincorporated ~sS-methionine. Radiolabeled proteins secreted either apically or basally by cUE cells were determined using scintillation spectroscopy, profiled by two-dimensional SDS-PAGE, and visualized using fluorography as previously described (45).…”

“…LSMeans of 36 inserts from three animals. pregnant endometrium (45) and the presence of crystalline inclusions in vivo and in vitro suggest that polarized cUE cells can be used to study the control of uterine proteins that contribute to an environment conducive to early embryonic growth and development.…”