Maintenance of the Corpus Luteum of Early Pregnancy in the Ewe. II. Prostaglandin Secretion by the Endometrium in vitro and in vivo1

Quantitative characterization of prostaglandins in the uterus of early pregnant cattle

“…The present data indicate that the pregnant day 15 and day 18 uterine flushings had much higher concentrations of PG than their cyclic counterparts. Our findings are consistent with the observed rise in PGF 2a and PGE 2 as well as 6-keto PGF 1a observed in the ewe (Ellinwood et al 1979, Bartol et al 1981, Marcus 1981, Lewis et al 1982, Shelton et al 1990). These studies are consistently showing that during pregnancy the luminal concentrations of PGF 2a by far exceed PGE 2 .…”

“…PG released from the endometrium not only reach blood vessels, but also appear in the uterine lumen. Early studies have demonstrated PGF 2a and PGE 2 in in vivo flushings (Ellinwood et al 1979, Bartol et al 1981, Shelton et al 1990. Additionally, the conversion Figure 3 The concentrations of the prostaglandins and metabolites vary with respect to day and status in uterine flushings.…”

“…These studies differ with respect to the relative amounts of PG production and are not consistent with the present data. Low levels of PGF 2a , rising not earlier than day 19, have been described either with or without accompanied change of even lower levels of PGE 2 (Ellinwood et al 1979, Figure 4 mRNA transcript abundance of PG synthases (PLA2G4A (A), PLA2G6 (B), PTGS2 (C), PTGFS (E), PTGES (G), and PTGIS (K)), the metabolic enzyme HPGD (I), the prostaglandin transporter PGT (D), and specific receptors (FP (F), PTGER2 (H) and PTGER4 (J), PTGIR (L), and PPARG (M)) in endometrium and trophoblast tissue. For both endometrium (left) and trophoblast tissue (right), equal amounts of total RNA was used for reverse transcription and subsequent qPCR.…”

“…As numerous in vitro studies demonstrated a shift from PGF 2a to PGE 2 production due to IFNT, an optimal PGE 2 to PGF 2a ratio during pregnancy favoring PGE 2 is generally accepted as an essential prerequisite of maternal contribution to successful establishment of pregnancy (Arosh et al 2004b). Earlier studies showing the presence of high levels of PGF 2a in the uterus lumen during pregnancy when compared with the cycle might be part of a general PG increase (Ellinwood et al 1979, Bartol et al 1981, but there is a lack of in vivo evidence for the concomitant outranging increase in PGE 2 . Comprehensive data on the presence of the different PG hormones in the uterine lumen of ruminants in vivo are missing.…”

Uterine blood flow, myometrial activity and their response to adenosine during the peri-implantation period in sheep

“…This signal results in the continued secretion of progesterone which is essential for the establishment and maintenance of pregnancy. Previous studies have shown that among the biochemical changes that occur in the uterus before implantation are increases in the rate of protein synthesis, in the concentration of prostaglandin (PG) F in caruncular (Findlay et al, 1981) and total (Ellinwood, Nett & Niswender, 1979) endometrial tissue, and a decrease in the net production of PGF in caruncular tissue (Findlay et al, 1981). Vascular (Greiss & Anderson, 1970a), and a diminished vasoconstrictor response of the uterine artery to periarterial sympathetic nerve stimulation (Pope & Stormshak, 1979).…”