Metabolism of Arachidonic Acid In Vitro by Bovine Blastocysts and Endometrium1

Abstract

Metabolism of arachidonic acid and prostaglandin F2 alpha by bovine blastocysts and endometrial slices recovered on Days 16 and 19 postmating was studied in vitro. In Experiment 1, arachidonic acid (10 microCi tritiated and 200 micrograms radioinert) was added to blastocysts and endometrial slices prior to incubation for 24 h. [3H]arachidonic acid ([3H]AA) and metabolites in extracts of culture medium and tissue homogenates were separated on columns of Sephadex LH-20. Elution profiles of [3H]AA and metabolites in extracts of culture medium revealed that 13, 14-dihydro-15-keto-PGF2 alpha (PGFM), Pge2, PGF2 alpha, and at least four unidentified compounds were produced by Day 16 and Day 19 blastocysts. Endometrial slices from both days of pregnancy produced 3H-prostaglandins. Experiment 2 was conducted to quantify PGE2, PGF2 alpha and PGFM in aliquots of culture medium from Day 16 and Day 19 blastocyst and endometrial incubates. These tissues were incubated with 200 micrograms of radioinert arachidonic acid. Day 16 blastocysts produced less (microgram/blastocyst; P less than 0.01) of each prostaglandin than Day 19 blastocysts (PGE2, 0.7 +/- 0.4 vs. 4.2 +/- 1.0; PGF2 alpha, 2.1 +/- 0.7 vs. 22.8 +/- 4.1; PGFM, 0.03 +/- 0.01 vs. 0.5 +/- 0.2). Endometrial slices produced PGE2, PGF2 alpha and PGFM, but quantities were not affected by day postmating or uterine horncorpus luteum relationships. The third experiment was conducted to determine directly if Day 19 blastocysts and endometrial slices metabolized [3H]PGF2 alpha to [3H]PGFM. Blastocysts and endometrial slices produced [3H]PGFM. Endometrial slices metabolized 34.3 +/- 1.5% of the [3H]PGF2 alpha to [3H]PGFM, while blastocysts metabolized 7.5 +/- 1.6% of the [3H]PGF2 alpha to [3H]PGFM. Results of this study indicate that bovine blastocysts and endometrial slices can metabolize [3H]AA in vitro. It is postulated that prostaglandins of blastocyst and endometrial orgin have a role in maintenance of early pregnancy in cattle.

PGF2α levels in Day 8 blood plasma are increased by the presence of one or more embryos in the uterus

“…Our results are consistent with other studies in utero, as the total amount of PGs were over three times higher in Day 13 pregnant after multiple ET than in cyclic heifers (Spencer et al, 2013). In particular, concentrations of PGF 2 α normally exceed several times that of PGE 2 (Bartol et al, 1981;Lewis et al, 1982;Shelton et al, 1990;Ulbrich et al, 2009). At such stages, PGs activate a number of IFNT-stimulated genes, and it seems that PGs could be important recognition signalling molecules in cattle (Spencer et al, 2013;Lonergan and Forde, 2014).…”

“…Similarly, pregnant cows on days 5 and 6 show concentrations four to five times higher for PGFM than for PGEM (Richardson et al, 2013), consistent with our results where PGF 2 α and PGE 2 concentrations were analysed on Day 8. The endometrium is not the only source of UF PGs, as bovine blastocysts produce substantial amounts of PGF 2 α with higher abundance of PGF 2 α than PGE 2 (Shemesh et al, 1979;Lewis et al, 1982). The reported increase in UF PGs, at least close to the implantation time, has been suggested to come from the embryonic side (Ulbrich et al, 2009;Spencer et al, 2013).…”

Prostaglandin production by horse embryos and the effect of co-culture of embryos with endometrium from pregnant mares

“…Embryos also secrete prostaglandins which may contribute to pregnancy maintenance (Lewis et al, 1982;Hyland et al, 1982;Hwang et al, 1988). Embryos of sheep and cattle secrete luteo¬ trophic factors which stimulate progesterone production by luteal cells (Hickey & Hansel, 1987) and prevent PGF-2a-induced regression of the CL (Vallet et al, 1988).…”

Effects of intrauterine infusion of oestradiol-17 and prostaglandin E-2 on luteal function in non-pregnant heifers

“…Intrauterine infusion of near physiological concentrations of oestradiol-17ß results in an extension of the functional lifespan of corpora lutea (CL) in the sow (Ford, Magness, Farley & Van Orden, 1982b). Prostaglandin (PG) E-2 is produced by cultured bovine blastocysts as early as Day 13 after mating (Shemesh et ai, 1979;Lewis, Thatcher, Bazer & Curl, 1982), and by ovine blastocysts by Day 14 (Lacroix & Kann, 1982). Uterine luminal and venous concentrations of PGE-2 are elevated on Day 15 in pregnant ewes (Ellinwood, Nett & Niswender, 1979).…”