Platelet-Activating Factor in Human Luteal Phase Endometrium1

Abstract

Platelet-activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine) is one of the most potent mediators of vascular permeability. PAF levels change in the rabbit endometrium just prior to implantation, which suggests that PAF may be a key substance transducing preimplantation embryonic signals. To study whether PAF was present in the human endometrium, and if so, to determine the cellular origin and hormonal regulation of endometrial PAF, specimens were obtained from 14 women (aged 23-42 yr) undergoing elective hysterectomy during the luteal phase of the cycle (plasma progesterone levels greater than 2 ng/ml). No specimens were taken from women with malignant uterine pathology. Stromal cells and epithelial glandular cells were separated by collagenase and DNAse digestion, and then cultured to confluence in vitro in medium 199. Radioimmunoassays of prostaglandin F (PGF) and prolactin in the culture media were used to confirm cell type and viability. PGF release into the culture medium from stromal cells was low (control 1.52 +/- 0.20 ng/ml), and unchanged by hormone treatment. In contrast, release of PGF from unstimulated glandular cells was 6.05 +/- 0.52 ng/ml, and was significantly increased (p less than 0.05) by estradiol or progesterone plus estradiol, to 12.17 +/- 1.67, and 8.60 +/- 0.81, respectively. Progesterone alone was without effect. Prolactin was secreted by stromal cell cultures, increasing steadily from 24 to 120 h. The levels in the medium were increased by progesterone. PAF activity was assessed by rabbit platelet aggregation and serotonin-release bioassays after lipid extraction and separation by thin-layer chromatography.(ABSTRACT TRUNCATED AT 250 WORDS)

Ovine Endometrium Synthesizes and Releases Platelet-Activating Factor, Which Can Cause the Release of Prostaglandin F2α by the Uterus in Situ1

“…Most uterine PAF activity was present within the endometrium. PAF was also found in human endometrial tissue, predominantly within the stromal cells of the endometrium [7]. In the current study, endometrial explants were used, and the possibility that the detected PAF originated from other cells within endometrium (e.g., endothelial cells, platelets, or polymorphonuclear leukocytes) cannot be excluded.…”

“…This is the first report of the release of PAF by the uterus in eutherian mammals. Alecozay et al [7] found that human stromal endometrial cells in culture only occasionally released small amounts of PAF into medium, even though significant concentrations of PAF were found within the corresponding cells. It should be noted, however, that those cultures were performed in medium 199 supplemented with 10% fetal calf serum.…”

“…In the latter case, PAF levels increased during the early luteal phase, but the presence of the implanted embryo substantially reduced the amount of PAF in surrounding endometrial tissue [6]. Alecozay et al [7] also found that human luteal-phase endometrium contained PAF; it was restricted to the endometrial stromal cells, and addition of progesterone to medium in vitro substantially increased accumulation of PAF in cells. Endometrial explants from the tammar wallaby [8] released PAF into culture medium in vitro; PAF release increased significantly as animals were released from delayed implantation, increasing as progesterone output increased from the CL.…”

Expression of platelet activating factors and its receptor in cat uterus during early pregnancy

“…However, it is also produced by a number of nonimmune cells such as endothelial (9), vascular, muscle (43), glomerular (13) and endometrial cells (4,5,7,45). PAF plays a role in many reproductive events (16), including ovulation (1), fertilization (27), implantation and early development of embryo (28).…”

“…PAF plays a role in many reproductive events (16), including ovulation (1), fertilization (27), implantation and early development of embryo (28). PAF has been determined in the uterus of rats (45), rabbits (5), dogs (35) and humans (4). It plays a significant role in mammalian reproduction (29,32).…”