Prostaglandin E2 Receptors: Expression and Possible Role During Endometrial Sensitization and Initiation of Decidualization in Rat Endometrium.
Bibliographic record
Abstract
Previous studies conducted in this laboratory suggest that prostaglandin E2 (PGE2) has a major role in the early events of decidualization in the rat. Once PGE2 is produced, this prostaglandin exerts its effect via a group of membrane GTP-binding protein (G protein)-coupled receptors classified as EPs including EP1, EP2, EP3 and EP4. Previous studies have shown that mRNAs for EP2-4, but not EP1, are expressed in rat endometrium sensitized for the decidual cell reaction. To further elucidate the roles of EP2-4 in uterine sensitization, the increase in endometrial vascular permeability and subsequent decidualization in response to a deciduogenic stimulus, we determined the expression of EP2, EP3 and EP4 in ovariectomized rats treated on the afternoon of the equivalent of day 4 of pseudopregnancy with estradiol (E2) and progesterone (P4), (equivalent to nidatory E2 to induce receptivity), or P4 alone (to maintain the neutral state). Endometrium was separated from myometrium at 0, 5 or 15 h after the hormone injections and protein was isolated. By western blot analysis we detected 1 isoform (60 kDa) for EP2, 2 isoforms (60 and 47 kDa) for EP3 and 1 isoform (40 kDa) for EP4. Nidatory E2 did not significantly change the expression of these receptors at any time examined. To study the expression of EPs during the initiation of decidualization, ovariectomized rats were treated with E2 and P4 to mimic pseudopregnancy and on day 5 of pseudopregnancy a bilateral intrauterine injection of sesame oil was given as a deciduogenic stimulus. Endometrial protein was isolated at 0 h and at 2, 4, 8, 16 or 32 h following the stimulus. We detected 3 isoforms for EP2 at 60, 47 and 37 kDa, 4 isoforms for EP3 at 60, 53, 47 and 37 kDa, and 1 isoform for EP4 at 40 kDa. At 32 h after the stimulus was given, the levels of the EP2-37 kDa isoform, the EP3-60 kDa isoform and the EP4-40 kDa isoform were significantly lower than for the non-stimulated (NS) at the same time point. In addition, the levels of the EP3-53 kDa isoform were significantly higher at 32 h stimulated than NS at the same time point. Moreover, this EP3-53 kDa isoform significantly increase at 32 h compared with 8 h and earlier times. Finally, to determine the role of EPs in the initiation of decidualization, we compared the ability of PGE2, Butaprost (a selective agonist of EP2), Sulprostone (a selective agonist of EP3), and L-902688 (a selective agonist of EP4) to increase endometrial vascular permeability (an early event in decidualization and as assessed by uterine Evans blue concentration 10 h after the unilateral intrauterine infusion of the compounds). The data indicated that PGE2 and EP4 agonist infusions produced very similar uterine Evans blue concentrations that were significantly higher than those resulting from the infusion of the vehicle, EP2 and EP3 agonists and from those in the non-infused horns. Because the rat endometrium differentially regulates the expression of EP2, EP3 and EP4 isoforms during sensitization and after an artificial deciduogenic stimulus was given and because EP4 was as effective as PGE2 in increasing endometrial vascular permeability, we suggest that EP4 is most likely the prostaglandin receptor involved in the initiation of decidualization in the rat. [This work was supported by the Canadian Institutes of Health Research.] (poster)
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".