Role of progesterone in regulating uteroovarian venous concentrations of PGF2 alpha and PGE2 during the estrous cycle and early pregnancy in ewes

Using transrectal ultrasound to examine the effect of exogenous progesterone on early embryonic loss in sheep

The financial impact of early embryonic loss in Australia may be as high as $137 million AUD/year. Embryos may be lost due to environmental conditions, or maternal factors such as nutrition or progesterone (P4) profiles. However, studies on the supplementation of P4 during early pregnancy have returned contradictory results, partly as a reliable method of detecting embryos in the early stages of gestation (<day 20) has yet be established. As such, Merino ewes (n = 62) were either not supplemented (control) or were given exogenous P4 at the time of insemination (day 0) or 3 days later (day 3). Transrectal ultrasound (TRUS) was performed on day 10, 12, 14, 17, 19 and 29 following laparoscopic artificial insemination. Transcutaneous ultrasound (TCUS) was performed on day 54 to confirm pregnancy and peripheral blood was collected for hormone analysis on day 19 to compare the accuracy of all three pregnancy diagnosis methods. Data were then analysed in developmental periods. The percentage of ewes detected as pregnant by TRUS during pre-, peri- and post implantation was 66% (41/62; day 12 and 14), 61% (38/62; day 17 and 19) and 58% (36/62; day 29), respectively. TCUS during established gestation recorded a pregnancy rate of 60% (37/62). The sensitivity of TRUS to correctly diagnose ewes as pregnant during pre-, peri- and post implantation was 68% (25/37), 89% (33/37) and 100% (36/36), respectively, while the sensitivity to correctly identify multiples was 49% (16/33), 60% (21/35) and 97% (34/35), respectively (P<0.05). The majority of embryonic loss occurred between pre- and peri- implantation (0.9±0.15 per ewe; P<0.001). No further loss was recorded after this point. Ewes that were given P4 at day 0 had significantly higher embryonic loss (77%) compared to the control (52%) and day 3-ewes (56%; P<0.05). These results show TRUS is a viable tool for investigating early embryonic loss and that the variability noted in previous P4 supplementation studies may be due to variation in time and length of treatment.

Novel concepts on the role of prostaglandins on luteal maintenance and maternal recognition and establishment of pregnancy in ruminants

In ruminants, the corpus luteum (CL) of early pregnancy is resistant to luteolysis. Prostaglandin (PG)E2 is considered a luteoprotective mediator. Early studies indicate that during maternal recognition of pregnancy (MRP) in ruminants, a factor(s) from the conceptus or gravid uterus reaches the ovary locally through the utero-ovarian plexus (UOP) and protects the CL from luteolysis. The local nature of the embryonic antiluteolytic or luteoprotective effect precludes any direct effect of a protein transported or acting between the gravid uterus and CL in ruminants. During MRP, interferon tau (IFNT) secreted by the trophoblast of the conceptus inhibits endometrial pulsatile release of PGF2α and increases endometrial PGE2. Our recent studies indicate that (1) luteal PG biosynthesis is selectively directed toward PGF2α at the time of luteolysis and toward PGE2 at the time of establishment of pregnancy (ESP); (2) the ability of the CL of early pregnancy to resist luteolysis is likely due to increased intraluteal biosynthesis and signaling of PGE2; and (3) endometrial PGE2 is transported from the uterus to the CL through the UOP vascular route during ESP in sheep. Intrauterine co-administration of IFNT and prostaglandin E2 synthase 1 (PGES-1) inhibitor reestablishes endometrial PGF2α pulses and regresses the CL. In contrast, intrauterine co-administration of IFNT and PGES-1 inhibitor along with intraovarian administration of PGE2 rescues the CL. Together, the accumulating information provides compelling evidence that PGE2 produced by the CL in response to endometrial PGE2 induced by pregnancy may counteract the luteolytic effect of PGF2α as an additional luteoprotective mechanism during MRP or ESP in ruminants. Targeting PGE2 biosynthesis and signaling selectively in the endometrium or CL may provide luteoprotective therapy to improve reproductive efficiency in ruminants.

Early pregnancy induced expression of prostaglandin E2 receptors EP2 and EP4 in the ovine endometrium and regulated by interferon tau through multiple cell signaling pathways

Prostaglandin E2 (PGE(2)) plays pleiotropic roles at fetal-maternal interface during establishment of pregnancy. The objectives of the study were to: (i) determine regulation of PGE2 receptors EP1, EP2, EP3, and EP4 in the endometrium during the estrous cycle and early pregnancy; and (ii) understand endometrial epithelial and stromal cell-specific hormonal regulation of EP2 and EP4 in sheep. Results indicate that: (i) early pregnancy induces expression of EP2 and EP4 but not EP1 and EP3 proteins in the endometrium on days 12-16 compared to that of estrous cycle; (ii) intrauterine infusion of interferon tau (IFNT) increases expression of EP2 and EP4 proteins in endometrium; and (iii) IFNT activates distinct epithelial and stromal cell-specific JAK, EGFR, ERK1/2, AKT, or JNK signaling module to regulate expression of EP2 and EP4 proteins in the ovine endometrium. Our results indicate a role for EP2 and EP4-mediated PGE(2) signaling in endometrial functions and establishment of pregnancy in ruminants.

What regulates placental steroidogenesis in 90-day pregnant ewes?

By day-90, the placenta secretes half of the circulating progesterone and 85% of the circulating estradiol-17beta [Weems YS, Vincent D, Tanaka Y, et al. Effects of prostaglandin F(2alpha) on sources of progesterone and pregnancy in intact, ovariectomized, and hysterectomized 90-100 day pregnant ewes. Prostaglandins 1992;43:203-22; Weems YS, Vincent DL, Nusser K, et al. Effects of prostaglandin F(2alpha) (PGF(2alpha)) on secretion of estradiol-17beta and cortisol in 90-100 day hysterectomized, intact, or ovariectomized pregnant ewes. Prostaglandins 1994;48:139-57]. Ovariectomy (OVX) or prostaglandin (PG) F(2alpha) (PGF(2alpha)) does not abort intact or OVX 90-day pregnant ewes and PGF(2alpha) regresses the corpus luteum, but does not affect placental progesterone secretion in vivo [Weems YS, Vincent D, Tanaka Y, et al. Effects of prostaglandin F(2alpha) on sources of progesterone and pregnancy in intact, ovariectomized, and hysterectomized 90-100 day pregnant ewes. Prostaglandins 1992;43:203-22]. Luteal progesterone secretion in vitro at day-90 of pregnancy in ewes is regulated by PGE(1)and/or PGE(2), not by ovine luteinizing hormone (LH; 3). Concentrations of PGE in uterine or ovarian venous plasma averaged 6 ng/ml at 90-100 days of pregnancy in ewes [Weems YS, Vincent DL, Tanaka Y, Nusser K, Ledgerwood KS, Weems CW. Effect of prostaglandin F(2alpha) on uterine or ovarian secretion of prostaglandins E and F(2alpha) (PGE; PGF(2alpha)) in vivo in 90-100 day hysterectomized, intact or ovariectomized pregnant ewes. Prostaglandins. 1993;46:277-96]. Ovine placental PGE secretion is regulated by LH up to day-50 and by pregnancy specific protein B (PSPB) after day-50 of pregnancy [Weems YS, Kim L, Humphreys V, Tsuda V, Weems CW. Effect of luteinizing hormone (LH), pregnancy specific protein B (PSPB), or arachidonic acid (AA) on ovine endometrium of the estrous cycle or placental secretion of prostaglandins E(2) (PGE(2)) and F(2alpha) (PGF(2alpha)), and progesterone in vitro. Prostaglandins Other Lipid Mediators 2003;71:55-73]. Indomethacin (INDO), a prostaglandin synthesis inhibitor [Lands WEM. The biosynthesis and metabolism of prostaglandins. Annu Rev Physiol 1979;41:633-46], lowers jugular venous progesterone [Bridges PJ, Weems YS, Kim L, et al. Effect of prostaglandin F(2alpha) (PGF(2alpha)), indomethacin, tamoxifen or estradiol-17beta on pregnancy, progesterone and pregnancy specific protein B (PSPB) secretion in 88-90 day pregnant ewes. Prostaglandins Other Lipid Mediators 1999;58:113-24] and inferior vena cava PGE of pregnant ewes with ovaries by half at day-90 [Bridges PJ, Weems YS, Kim L, LeaMaster BR, Vincent DL, Weems CW. Effect of prostaglandin F(2alpha) (PGF(2alpha)), indomethacin, tamoxifen or estradiol-17beta on prostaglandin E (PGE), PGF(2alpha) and estradiol-17beta secretion in 88-90 day pregnant sheep. Prostaglandins Other Lipid Mediators 1999;58:167-78]. In addition, treatment of 90 day ovine diced placental slices with androstenedione in vitro increased placental estradiol-17beta, but treatment with PGF(2alpha)in vitro did not decrease placental progesterone secretion, which indicates that ovine placenta progesterone secretion is resistant to the luteolytic action of PGF(2alpha) [Weems YS, Bridges PJ, LeaMaster BR, Sasser RG, Vincent DL, Weems CW. Secretion of progesterone, estradiol-17beta, prostaglandins (PG) E (PGE), F(2alpha) (PGF(2alpha)), and pregnancy specific protein B (PSPB) by day 90 intact or ovariectomized pregnant ewes. Prostaglandins Other Lipid Mediators 1999;58:139-48]. This also explains why ovine uterine secretion of decreased around day-50 [Weems YS, Kim L, Humphreys V, Tsuda V, Weems CW. Effect of luteinizing hormone (LH), pregnancy specific protein B (PSPB), or arachidonic acid (AA) on ovine endometrium of the estrous cycle or placental secretion of prostaglandins E(2) (PGE(2)) and F(2alpha) (PGF(2alpha)), and progesterone in vitro. Prostaglandins Other Lipid Mediators 2003;71:55-73], when placental estradiol-17beta secretion is increasing [Weems C, Weems Y, Vincent D. Maternal recognition of pregnancy and maintenance of gestation in sheep. In: Reproduction and animal breeding: advances and strategies. Enne G, Greppi G, Lauria A, editors, Elsevier Pub., Amsterdam 1995. p. 277-93]. Treatment of 90 day pregnant ewes with estradiol-17beta+ PGF(2alpha), but not either treatment alone, caused a linear increase in both estradiol-17beta and PGF(2alpha) and ewes were aborting [Bridges PJ, Weems YS, Kim L, Sasser RG, LeaMaster BR, Vincent DL, Weems CW. Effect of prostaglandin F(2alpha) (PGF(2alpha)), indomethacin, tamoxifen or estradiol-17beta on pregnancy, progesterone and pregnancy specific protein B (PSPB) secretion in 88-90 day pregnant ewes. Prostaglandins Other Lipid Mediators 1999;58:113-24; Bridges PJ, Weems YS, Kim L, LeaMaster BR, Vincent DL, Weems CW. Effect of prostaglandin F(2alpha) (PGF(2alpha)), indomethacin, tamoxifen or estradiol-17beta on prostaglandin E (PGE), PGF(2alpha) and estradiol-17beta secretion in 88-90 day pregnant sheep. Prostaglandins Other Lipid Mediators 1999;58:167-78]. Pregnant ewes OVX on day 83 of pregnancy and placental slices cultured in vitro secretes 2-3-fold more estradiol-17beta, PSPB, PGE, and progesterone than placental slices from 90 day intact pregnant ewes, but placental PGF(2alpha) secretion by placental slices from intact or OVX ewes did not change [Denamur R, Kann G, Short R V. How does the corpus luteum of the sheep know that there is an embryo in the uterus? In: Pierrepont G, editor. Endocrinology of pregnancy and parturition, vol. 2. Cardiff, Wales, UK: Alpha Omega Pub Co.; 1973. p. 4-38]. The objective of these experiments was to determine what regulates ovine placental progesterone and estradiol-17beta secretion at day-90 of pregnancy, since the hypophysis [Casida LE, Warwick J. The necessity of the corpus luteum for maintenance of pregnancy in the ewe. J Anim Sci 1945;4:34-9] or ovaries [Weems CW, Weems YS, Randel RD. Prostaglandins and reproduction in female farm animals. Vet J 2006;171:206-28] are not necessary after day-55 to maintain pregnancy. In Experiment 1, diced placental slices from day-90 intact or OVX pregnant ewes that were ovariectomized or laparotomized and ovaries were not removed on day 83 were collected on day-90 and incubated in vitro in M-199 with Vehicle, ovine luteinizing hormone (oLH), ovine follicle stimulating hormone (oFSH), ovine placental lactogen (oPL), PGE(l), PGE(2), PGD(2), PGI(2), insulin-like growth factor (IGF) 1 or 2 (IGF(l); IGF(2)), leukotriene C(4) (LTC(4)), platelet activating factor (PAF) 16 or 18 (PAF-16; PAF-18) at doses of 0, 1, 10, or 100ng/ml for 4h. In Experiment 2, placental slices from day-90 intact and OVX (intact or OVX laporotomized 7 days earlier) pregnant ewes were incubated in vitro with vehicle, INDO, Meclofenamate (MECLO), PGE(l), PGE(2), INDO+PGE(1), MECLO+PGE(l), INDO+PGE(2), or MECLO+PGE(2) for 4h. Media were analyzed for progesterone, estradiol-17beta, PGE, or PGF(2alpha) by RIA. Hormone data in media were analyzed in Experiment 1 by a 2x3x13 and in Experiment 2 by a 2x9 Factorial Design for ANOVA. In Experiment 1, placental progesterone, PGE, or estradiol-17beta secretion were increased (P< or =0.05) two-fold by OVX. Progesterone was not increased (P> or =0.05) by any treatment other than OVX and only FSH increased (P< or =0.05) estradiol-17beta secretion by placental slices in both OVX and intact ewes 90-day pregnant ewes. In Experiment 2, INDO or MECLO decreased (P< or =0.05) placental progesterone secretion by 88% but did not decrease (P> or =0.05) placental estradiol-17beta secretion from intact or OVX ewes. PGE(l) or PGE(2) increased (P< or =0.05) progesterone secretion only in ewes treated with INDO or MECLO. It is concluded that FSH probably regulates day-90 ovine placental estradiol-17beta secretion, while PGE(l) or PGE(2) regulates day-90 placental progesterone secretion.

Preovulatory, postovulatory, and postmaternal recognition effects of concentrations of progesterone on embryonic survival in the cow

Although fertilization rate usually is very high when male fertility is normal, pregnancy rates are below expectations when defined by the birth of live offspring in response to first service. Factors that affect establishment and retention of pregnancy include 1) preovulatory influences on the follicle and oocyte, 2) early postovulatory uterine and luteal function, 3) concentrations of hormones associated with trophoblastic and endometrial function during maternal recognition of pregnancy, and 4) less-well understood factors during the peri-attachment period. For example, decreased progesterone during preovulatory follicular development leads to a persistent follicle, premature resumption of meiosis, and a high incidence of embryonic death between the 2- and 16-cell stages. Elevated PGF(2alpha) during d 4 to 9 of the estrous cycle not only caused luteolysis but also had a direct embryotoxic effect during the morula-to-blastocyst transition. Ideal conditions during placentation and attachment are not clearly defined. Late embryonic mortality might be increased after ovulation of persistent or immature follicles. Nominal increases in secretion of PGF(2alpha) between d 30 and 35 might be important for attachment and placentation. Lower survival of embryos from wk 5 to wk 7 to 9 of gestation in the cow was associated with lower circulating concentrations of progesterone on wk 5. To maximize embryonic survival in the cow, management must provide high progesterone before estrus, quality detection of estrus, and timely insemination. Luteolytic influences of estradiol-17beta or PGF(2alpha) must be minimized early after mating and during maternal recognition of pregnancy, and high progesterone is needed during the late embryonic/early fetal period.

Prostaglandins and reproduction in female farm animals

Prostaglandins impact on ovarian, uterine, placental, and pituitary function to regulate reproduction in female livestock. They play important roles in ovulation, luteal function, maternal recognition of pregnancy, implantation, maintenance of gestation, microbial-induced abortion, parturition, postpartum uterine and ovarian infections, and resumption of postpartum ovarian cyclicity. Prostaglandins have both positive and negative effects on reproduction; they are used to synchronize oestrus, terminate pseudopregnancy in mares, induce parturition, and treat retained placenta, luteinized cysts, pyometra, and chronic endometritis. Improved therapeutic uses for prostaglandins will be developed when we understand better their involvement in implantation, maintenance of luteal function, and establishment and maintenance of pregnancy.

Effect of luteinizing hormone (LH), pregnancy specific protein B (PSPB), or arachidonic acid (AA) on ovine endometrium of the estrous cycle or placental secretion of prostaglandins E2 (PGE2) and F2alpha (PGF2alpha) and progesterone in vitro

The objective of this experiment was to determine the effect of AA, LH, or PSPB on secretion of PGE2, PGF2alpha, or progesterone by ovine caruncular endometrium of the estrous cycle or placental tissue of pregnancy in vitro. Ovine caruncular endometrium of the estrous cycle (days 8, 11, 13, and 15) or caruncular/placental tissue on days 8, 11, 13, 15, 20, 30, 40, 50, 60, and 90 postbreeding were incubated in vitro with vehicle, AA, LH, or PSPB in M-199 for 4 and 8 h. Secretion of PGF2alpha by caruncular endometrium of non-bred ewes on days 13 and 15 and by caruncular/placental tissue of bred ewes on days 13, 15, 20, 30, and 40 was increased (P < or = 0.05) when incubated with vehicle and declined (P < or = 0.05) after day-40 in bred ewes. Secretion of PGF2alpha by day-15 caruncular endometrium of non-bred ewes and bred ewes was increased (P < or = 0.05) by AA on days 13 and 15 and by LH on day-15. Secretion of PGF2alpha by caruncular/placental tissue from bred ewes was (P < or = 0.05) by AA on days 13, 15, 20, 30, and 40 and by LH on days 15, 20, 30, and 40, after which the response decreased (P < or = 0.05). Secretion of PGF2alpha by caruncular endometrium of non-bred ewes during the estrous cycle or by caruncular/placental tissue of bred ewes during the first trimester was not affected by PSPB (P > or = 0.05). Secretion of PGE2 by caruncular endometrium of non-bred ewes did not change (P > or = 0.05) and was increased (P < or = 0.05) by caruncular/placental tissue on days 13-90 from bred ewes when incubated with vehicle. Secretion of PGE2 by endometrium from non-bred ewes was not affected (P > or = 0.05) by AA, LH, or PSPB, but was increased (P < or = 0.05) by AA or LH on days 13-50 and by PSPB on days 60 and 90 when incubated with caruncular/placental tissue from bred ewes. Secretion of progesterone by placental tissue of bred ewes increased (P < or = 0.05) on day-50 and continued to increase through day-90. In summary, uterine/placental tissue secretion of PGF2alpha is not reduced until the end of the first trimester of pregnancy in ewes. In addition, LH appears to play a role in luteolysis of non-bred ewes by stimulating caruncular endometrial secretion of PGF2alpha and on day-5 postbreeding to prevent luteolysis during early pregnancy by stimulating caruncular/placental secretion of PGE2 throughout the first trimester of pregnancy in sheep. Secretion of PGE2 by caruncular/placental tissue after day-50 of pregnancy appears to be regulated by PSPB, not LH.

Prostaglandin E2, prostaglandin F2 alpha and endothelin-1 production by cow oviductal epithelial cell monolayers: effect of progesterone, estradiol 17 beta, oxytocin and luteinizing hormone

The optimal oviductal environment, including contractile activity for gamete transport, fertilization and early embryonic development, is mediated by physiological and anatomical changes in the oviduct during the estrous cycle. Oviductal epithelial cell culture was utilized to investigate the effect of ovarian steroids (progesterone [P4] and estradiol 17 beta [E2]), oxytocin (OT) and luteinizing hormone (LH) on the local production of prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha) and endothelin-1 (ET-1) in the cow oviduct. Epithelial cells isolated from oviducts collected during the follicular phase were cultured in M199 under standard culture conditions until monolayer formation. Then the cells were trypsinized and plated at a density of 3 x 10(4)/mL/well and cultured again until subconfluency, at which time the cells were incubated for 4 or 24 h with M199 only (control), high P4 (H-P4; 1 microgram/mL), low P4 (L-P4; 10 ng/mL), E2 (1 ng/mL), LH (10 ng/mL), OT (10(-9) M) ET-1 (10(-9) M), PGE2 (10(-8) M) PGF2 alpha (10(-9) M) or their combination (H-P4 + E2, L-P4 + E2, LH + E2, ET-1 + E2, L-P4 + E2 + LH and H-P4 + E2 + LH). The production of both PG and ET-1 was increased by E2 + low P4 and LH + E2 + low P4 (P < 0.05), while LH + E2 enhanced the production of PGF2 alpha and ET-1 (P < 0.05). Moreover, E2 + ET-1 stimulated PG production (P < 0.05). However, OT had no effect on the production of any of these substances. These results suggest that the preovulatory LH surge, together with locally re-circulated high levels of E2 from the Graafian follicle and basal P4 from regressing corpus luteum (CL), induces the maximum stimulatory effect on oviductal PGE2, PGF2 alpha and ET-1 production during the periovulatory period. Consequently, the elevated local ET-1 concentration during periovulatory period may induce the high contractile activity of the oviduct and, at the same time, the stimulation of PG production. Thus, ET-1 may act as a local amplifier for oviductal PG production stimulated by LH and ovarian steroids.

Involvement of ovarian steroids in basal and oxytocin-stimulated prostaglandin (PG) F2 alpha secretion by the bovine endometrium in vitro

It is assumed that exposure of endometrium to spontaneously secreted luteal hormones stimulates PGF2 alpha secretion and modifies oxytocin (OT) influence on the bovine uterus. At first, the time-dependent effect of endogenous luteal products on endometrial PGF2 alpha secretion was examined. Endometrial strips (100 mg) from slaughtered heifers (Days 11 to 17 of the cycle) were incubated alone or with luteal cells (1 x 10(5) cells/mL). The highest PGF2 alpha secretion by the endometrium under influence of hormones secreted from luteal cells was observed after 12 h of incubation compared with the control (P < 0.001). Then, endometrium (Days 11 to 17) was incubated with luteal cells and concomitantly with antagonists of P4 and OT. The P4 antagonist prevented the stimulatory effect of endogenous luteal hormones on PGF2 alpha secretion (P < 0.05), but the OT antagonist did not. Further, direct effects of exogenous P4, OT and estradiol (E2) on endometrial PGF2 alpha secretion (Days 11 to 17) were examined. Both OT and P4 increased PGF2 alpha secretion (P < 0.05); E2 alone had no effect on PGF2 alpha secretion, but it amplified the P4 effect (P < 0.05). Finally, we studied the effect of endogenous luteal products on OT-stimulated PGF2 alpha secretion from endometrium. When endometrium (Days 11 to 17) was incubated without luteal cells, OT stimulated PGF2 alpha secretion (P < 0.001), whereas incubation of endometrium with luteal cells abolished the stimulatory effect of OT on PGF2 alpha secretion (P < 0.001). These treatments did not affect PGF2 alpha secretion from the endometrium collected on Days 1 to 4. In conclusion, P4 stimulates PGF2 alpha secretion by the endometrium and E2 amplifies this effect. As long as the endometrium is under the influence of P4, ovarian OT does not affect PGF2 alpha secretion.

PGE2 induces its own secretion in vitro by bovine 270-day placenta but not by 200-day placenta

Two separate experiments were conducted to determine whether prostaglandin (PG) E2 stimulates the secretion of progesterone by 270- or 200-day Brahman placentas in vitro. Secretion of progesterone, PGF2alpha, pregnancy specific protein B, or estradiol-17beta by 270-day Brahman placentas was not affected (p > or = 0.05) by PGE2, during the 4-h incubation period at the doses tested. Indomethacin or meclofenamic acid decreased (p < or = 0.05) 270-day Brahman placental secretion of PGE and PGF2alpha by 98 and 60%, respectively. However, PGE2 induced (p < or = 0.05) its own secretion, but not the secretion of PGF2alpha (p > or = 0.05), by 270-day Brahman placentas, even in the presence of indomethacin or meclofenamic acid at a dose of 100 ng/mL. Also, secretion of 8-Epi-PGE2 by Day 270 Brahman placentas was increased (p < or = 0.05) by PGE2. Secretion of progesterone, estradiol-17beta, or pregnancy specific protein B by 200-day Brahman placentas was not affected by PGE2, 8-Epi-PGE2, PGF2alpha, estradiol-17beta, or trichosanthin during the 4- or 8-h incubation period (p > or = 0.05). Secretion of estradiol-17beta at 8 h was lower (p < or = 0.05) in all treatment groups and did not differ (p > or = 0.05) among the 8-h incubation treatment groups. Secretion of PGE by 200-day Brahman placentas was reduced (p < 0.05) by indomethacin 72 and 82% and by meclofenamic acid 72 and 96%, respectively, at 4 and 8 h when compared to controls. Secretion of PGF2alpha was reduced (p < or = 0.05) 71 and 86% by indomethacin or 89 and 89% by meclofenamic acid at 4 and 8 h, respectively, and did not differ (p > or = 0.05) between 4 and 8 h of incubation. PGE2 did not (p > or = 0.05) induce secretion of PGE above what was added in any treatment group. PGE in culture media was increased (p < or = 0.05) by 8-Epi-PGE2, pregnancy specific protein B, and the 100 ng/mL PGF2alpha dose (p < or = 0.05), but not by PGE2, progesterone, estradiol-17beta, 8-Epi-PGF2alpha, or trichosanthin. Secretion of PGF2alpha by 200-day Brahman placentas was not affected (p > or = 0.05) by 8-Epi-PGE2, progesterone, or estradiol-17beta, but PGF2alpha secretion was increased (p < or = 0.05) by trichosanthin or PGE2, even in the presence of indomethacin or meclofenamic acid. It is concluded that PGE does not affect secretion of progesterone by 200- or 270-day bovine placentas, but, pregnancy specific protein B may regulate placental secretion of PGE. Also, indomethacin and meclofenamic may affect enzymes converting PGH to PGE rather than acting only on cyclooxygenase because indomethacin and meclofenamic acid lowered PGE secretion by 270-day Brahman placentas more than they lowered PGF2alpha. In addition, it is concluded that PGE2 can induce bovine placental secretion of PGE, but this is dependent upon the stage of gestation.

Temporal relationships between oxytocin and 13,14-dihydro-15-keto-prostaglandin F2 alpha pulses in ovariectomized ewes

The primary objective was to evaluate the role of non-ovarian oxytocin in the initiation of pulses of PGF2 alpha, as measured by peripheral concentrations of 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM). A 2 x 2 factorial arrangement of estradiol and progesterone treatments was administered to groups of five ewes after ovariectomy on Day 12. Progesterone (10 mg) was administered at 0700 and 1900 hr on Day 12, and then either progesterone or its vehicle was administered on Days 13 and 14. Silastic implants, either empty or containing estradiol, was administered at ovariectomy. Oxytocin and PGFM were measured in jugular blood samples withdrawn from an indwelling catheter at 5-min intervals for 8 hr on Day 15. Statistically significant pulses of oxytocin, presumably of posterior pituitary origin, were detected in all ewes. Approximately one-half of the oxytocin pulses preceded a pulse in PGFM concentrations by 10 min or less. These pulses tended (P = 0.09) to have a longer duration than those not linked to pulses of PGFM. The number of PGFM pulses that followed or did not follow an oxytocin pulse by 10 min or less was similar (P > 0.2). The amplitude and duration of oxytocin-linked PGFM pulses were greater (P = 0.05) than non-linked pulses. Although several explanations for the lower than anticipated temporal relationship between oxytocin and PGFM pulses are possible, the finding that oxytocin-related PGFM pulses are distinguishable from other pulses is consistent with the concept that oxytocin initiates robust pulses in PGF2 alpha secretion.

Short-term studies of ovarian metabolism in the ewe

The ovarian uptake of metabolites in anaesthetised ewes was determined. In both studies, catheters were inserted into the ovarian vein and femoral artery, and Transonic flow transducers were placed around the ovarian arterio-venous plexus. Arterio-venous differences in glucose, lactate, free fatty acids (FFA), 3-hydroxybutyrate (3-OHB), acetate, cholesterol and progesterone and oestradiol-17 beta levels were determined every 10 min over a 3.5 h period. In study one, glucose uptake was significant in three sheep, and one sheep only had a significant uptake of FFA. Ovarian 3-OHB uptake was significant in two sheep. significant uptake of acetate or cholesterol was identified in one sheep. Progesterone secretion was significant in three sheep and two sheep had significant progesterone uptake. In study 2, glucose uptake was significant in four sheep and lactate release was significant in the same sheep. There was uptake of FFA and 3-OHB, cholesterol, and acetate in each of three different sheep. Oestradiol-17 beta output was significant for sheep in oestrus and prooestrus. While the effects of gonadotrophin-releasing hormone (GnRH) treatment were confounded by time spent under anaesthesia, exogenous GnRH appeared to have no significant effect on the uptake of most metabolites and steroid hormone outputs. The metabolic requirements for energy and precursors for progesterone was small. Glucose was the major source of energy for the ovary and appears to be metabolised through anaerobic pathways, as indicated by significant lactate output.

Effects of prostaglandin F2 alpha (PGF2 alpha) on secretion of pregnancy specific protein B (PSPB) and placentome weights in intact or ovariectomized 90 to 100 day pregnant ewes

Vehicle or 8 or 16 mg PGF2 alpha/58 kg/body weight (BW) was given intramuscularly to intact or ovariectomized 90 to 100 day pregnant ewes in two separate experiments. Treatment with 8 mg PGF2 alpha in intact 90 to 100 day pregnant ewes increased (P < or = 0.05) placentome weights, but not in ovariectomized 90 to 100 day pregnant ewes (P > or = 0.05). Concentrations of PSPB in uterine venous plasma of control 90 to 100 day intact pregnant ewes over the 72 hour sampling period averaged 52 +/- 5 ng/ml. Profiles of PSPB in uterine plasma in the 16 mg PGF2 alpha/58 kg/BW-treated ewes differed (P < or = 0.05) from control or 8 mg PGF2 alpha-treated 90 to 100 day intact pregnant ewes. Pregnancy specific protein B was increased (P < or = 0.05) at 64 hr in intact 90 to 100 day pregnant ewes by treatment with 8 mg PGF2 alpha/58 kg/BW. There was a quadratic increase (P < or = 0.09) in PSPB in uterine venous plasma of all three treatment groups of intact 90 to 100 day pregnant ewes. Concentrations of PSPB in uterine venous plasma of control 90 to 100 day ovariectomized pregnant ewes over the 72 hr treatment period averaged 90 +/- 5 ng/ml. Profiles of PSPB did not differ among the vehicle, 8 mg PGF2 alpha or 16 mg PGF2 alpha-treated ovariectomized 90 to 100 day pregnant ewes. There was a quadratic increase (P < or = 0.10) in PSPB in uterine venous plasma of ovariectomized 90 to 100 day pregnant ewes treated with 8 or 16 mg PGF2 alpha/58 kg/BW. It is suggested that PSPB may have a role in regulating placental steroidogenesis.

Prostaglandin E2 levels in uterine tissues and its relationship with uterine and luteal progesterone during the estrous cycle in dairy cows

Endometrial tissue homogenates obtained at luteal and follicular stages of the estrous cycle were determined for prostaglandin E2 and progesterone contents by EIA and RIA, respectively. In Experiment 1, the concentrations and changes of PGE2 in uterine tissues collected by biopsy before slaughter and subsequent samples collected at 30, 60 and 90 min after slaughter were measured. No significant differences were observed in the concentration of PGE2 preslaughter or at 30 and 60 min post slaughter. However, there was a significant decrease (P<0.01) in PGE2 concentration 90 min post slaughter. In Experiment 2, the concentrations of PGE2 in the ipsilateral and contralateral horns in relation to corpus luteum function were compared. A significant (P<0.05) interaction was found between stages of estrous cycle (luteal vs follicular) based on CL progesterone content, and type of uterine horn (ipsilateral vs contralateral) on uterine PGE2 levels. The PGE2 concentration was significantly higher (P<0.01) at luteal phase than at follicular phase. During the luteal phase PGE2 concentrations in tissues of the uterine horn ipsilateral to the corpus luteum was significantly higher (P<0.01) than the contralateral horn. The PGE2 concentration was low and did not differ significantly between horns during follicular phase. A parallel increase (luteal: high) and decrease (follicular: low) in PGE2 and progesterone concentrations were observed. Correlations were observed for CL progesterone and uterine PGE2 concentrations as well as for PGE2 and progesterone concentrations in uterine tissues (r=0.70 and r=0.60, respectively). The results show that the increase in PGE2 concentrations in uterine tissues coincides with the high uterine progesterone concentrations during luteal phase.

Prostaglandin E2 production by uterine stromal cell line UIII: regulation by estradiol and evidence of an ethanol action

We have recently established a uterine stromal cell line (UIII). The purpose of the present study was to determine whether these cells have retained the ability to produce and release prostaglandins after several passages and whether this production was regulated. UIII cells, grown in basal conditions, released a very low amount (40.6 +/- 2.9 pg/24h/10(6) cells) of prostaglandin E2 (PGE2) though cellular content was more elevated (192 +/- 23 pg/10(6) cells). Ethanol increased the cellular content but decreased the release of PGE2, whereas estradiol 17 beta (E2) increased it in a dose-dependent manner, but had no effect on the cellular content. The PGE2 release by cells grown in medium containing 10 microM arachidonate (AA) reached 1.39 +/- 0.05 ng/24h/10(6) cells, and was further increased to 2.1 +/- 0.1 ng/24 h/10(6) cells by the addition of ethanol. Under the latter condition, E2 was ineffective. This study also showed that UIII cells expressed an immunoreactive pancreatic type 14 kD PLA2. A substantial increased 14 kD PLA2 expression was observed in ethanol-treated cells, suggesting that ethanol-effect on prostaglandin production might be partly mediated by PLA2 increase. Medium supplementation with arachidonate also resulted in a significant increase of intracellular 14 kD PLA2 expression. The present results showed that uterine stromal UIII cells have retained the enzymatic machinery to produce PGE2. Moreover these data demonstrate that ethanol and E2 affect differently uterine PGE2 production.

Does exogenous progestogen alter the relationships among PGF2 alpha, 13,14-dihydro-15-keto-PGF2 alpha, progesterone, and estrogens in ovarian-intact ewes around the time of luteolysis?

The exact mechanisms controlling uterine secretion of PGF2 alpha are not known. An animal model in which progestogen concentrations are kept high and corpora lutea are allowed to regress should be useful for studying the effects of progestogen and estrogens on uterine secretion of PGF2 alpha. Thus, the primary objectives of this study with ovarian-intact ewes were to determine 1) the effect of 6 alpha-methyl-17 alpha-hydroxyprogesterone acetate (MPA) on luteal life span and changes in jugular and vena caval concentrations of PGF2 alpha, 13,14-dihydro-15-keto-PGF2 alpha (PGFM), progesterone, and estrogens around the time of luteolysis, and 2) the relationships among changes in those compounds. The results indicate that MPA 1) reduced (P < .05) vena caval and jugular PGF2 alpha and PGFM concentrations, 2) did not affect luteal life span or progesterone concentrations, 3) increased (P < .05) jugular concentrations of estrogens, and 4) prolonged (P < .05) the interestrous interval by 7 d. Stepwise regression procedures indicated that MPA disrupted a number of the relationships among PGF2 alpha, PGFM, progesterone, and estrogens in vena caval and jugular plasma. Ovarian-intact, MPA-treated ewes may be useful for determining the mechanisms involved in controlling uterine secretion of PGF2 alpha.

Luteal maintenance during early pregnancy in the pig: role for prostaglandin E2

We previously demonstrated that prostaglandin E2 (PGE) directly inhibits prostaglandin F2 alpha (PGF)-induced regression of individual pig corpora lutea (CL) in a dose dependent manner. The present experiments were conducted to 1) characterize and compare uterine secretion of PGE and PGF during the estrous cycle and early pregnancy and 2) evaluate the local effect of the conceptus on uterine prostaglandin secretion and associated CL function in unilaterally pregnant pigs. In Experiment 1, utero-ovarian venous blood samples were collected from two nonpregnant and two pregnant gilts at 3-h intervals from day 10 through 16 (first day of estrus or mating = day 0) for quantitation of uterine PGE and PGF secretion. In Experiment 2, gilts (n = 4) were made unilaterally pregnant on day 2, and utero-ovarian venous catheters were placed bilaterally to determine if differences in PGE and/or PGF secretion might account for the known luteotrophic/antiluteolytic effect of the gravid uterine horn on the CL of the ipsilateral ovary. During the estrous cycle (Experiment 1), pulsatile secretion of PGF increased markedly on day 13 and continued to increase through day 16. PGE secretion also increased from day 13 to 16 of the estrous cycle; however, concentrations of PGE remained at least 3-fold lower than those of PGF. In contrast to changes in non-mated gilts, prostaglandin secretion in mated gilts peaked earlier (day 11-12), with PGE predominating. Thereafter, both PGE and PGF secretion declined to basal levels where they remained through day 16 of pregnancy. During unilateral pregnancy (Experiment 2), PGF concentration in nongravid and gravid horns was similar (P > 0.8). In contrast, PGE concentrations were greater (P < 0.06) in utero-ovarian venous blood draining the gravid uterine horn. This increase in PGE was associated with enhanced CL function on the ipsilateral ovary as evidenced by an elevated progesterone content and concentration as well as increased CL weights. These data are consistent with a role for conceptus-associated increases in uterine PGE secretion in the local stimulation of luteal function during early pregnancy in the pig.

Effect of prostaglandin F2 alpha on uterine or ovarian secretion of prostaglandins E and F2 alpha in vivo in 90-100 day hysterectomized, intact or ovariectomized pregnant ewes

Vehicle or 8 or 16 mg of PGF2 alpha per 58 kg body weight was given intramuscularly to intact, hysterectomized or ovariectomized 90-100 day pregnant ewes in three separate experiments. Both doses of PGF2 alpha increased PGF2 alpha in ovarian venous plasma compared with controls at 72 hr post treatment in intact (P < or = 0.05) but did not in hysterectomized (P > or = 0.05) 90-100 day pregnant ewes. Concentrations of PGE in ovarian venous blood of intact ewes did not differ (P > or = 0.05) between treatment groups and were equivalent to concentrations of PGE determined in uterine venous plasma. PGE was decreased in ovarian venous plasma by PGF2 alpha in hysterectomized ewes (P < or = 0.07). PGE in uterine venous plasma averaged 6 ng/ml over the 72-hr treatment period in intact and ovariectomized 90-100 day pregnant ewes and was 12 fold greater (P < or = 0.05) than PGF2 alpha which averaged 500 pg/ml in uterine venous plasma. Both PGF2 alpha and PGE increased (P < or = 0.05) by 64 hr in uterine venous plasma of the 8 mg PGF2 alpha-treated intact pregnant ewes. A significant quadratic increase (P < or = 0.05) was observed for PGF2 alpha and PGE in the vehicle and both PGF2 alpha treatment groups of intact ewes at the end of the 72-hr sampling period. It is concluded that the uterus and ovaries secrete significant quantities of PGF but little PGF2 alpha during midgestation. In addition, PGF2 alpha increased uterine secretion of PGE in vivo. PGE may be a placental stimulator of ovine placental secretion of progesterone or PGE may protect placental steroidogenesis from actions of PGF2 alpha.

Jugular plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F2 alpha in prepubertal beef heifers treated with progestogen then challenged with oxytocin

Prepubertal Angus crossbred heifers (n = 24) between 8 and 10 mo of age were used to determine if progestogen treatment would enhance jugular concentrations of 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) after oxytocin (OT) injections. Heifers were stratified by age and weight and allotted to randomized treatments in a 2 x 2 factorial arrangement. Heifers were treated with either a norgestomet (NOR) implant (6 mg) for 9 d or no implant (0 mg; BLK). On d 8 of NOR treatment, jugular veins were catheterized and, on d 9, blood samples were collected every 15 min for 165 min. The first four samples were used to determine basal PGFM concentrations (an indirect measure of uterine PGF2 alpha release). After collection of the fourth sample, either OT (100 IU) or saline (0 IU; SAL) was injected via the jugular catheter. After the 165-min sample was collected, NOR implants were removed. Beginning 48 h after implant removal, a second 165- min blood sampling period was initiated. Average progesterone concentrations were less than 1 ng/ml during both bleeding periods. Within treatment, PGFM concentrations were similar between the first and second sampling periods; therefore, data within treatment were combined. Basal PGFM concentrations were higher (P < .01) in NOR-treated than in BLK heifers. Oxytocin did not increase PGFM concentrations in BLK-OT heifers; however, a marked increase in PGFM was detected in the NOR-OT heifers in response to oxytocin. Average PGFM concentration was greatest (P < .0001) in NOR-OT heifers, and PGFM profiles differed (P < .0001) between NOR-OT and each of the other treatment groups. Results from this study indicate that NOR increases basal PGFM and may "condition" the uterus to respond to OT in prepubertal heifers.

Adenosine facilitates the response to HCG, PGE1 or PGE2 and inhibits the response to PGF2 alpha by HCG-stimulated ovine luteal cells in vitro

Dispersed ovine luteal cells collected on day 7 or 16 postestrus were incubated in vitro with hCG, PGE1 or PGE2 in the presence or absence of adenosine, dipyridamole (inhibitor of adenosine uptake) or PGF2 alpha in two separate experiments. Secretion of progesterone was increased by hCG, PGE1 or PGE2 when incubated with day 7 luteal cells (P less than or equal to 0.05) which was increased further when co-incubated with adenosine (P less than or equal to 0.05). PGF2 alpha alone or in the presence of hCG decreased (P less than or equal to 0.05) the secretion of progesterone by day 7 luteal cells, PGF2 alpha decreased post treatment cell viability with or without hCG (P less than or equal to 0.05) and adenosine reduced (P less than or equal to 0.05) the inhibitory effect of PGF2 alpha on hCG actions and luteal cell viability. Day 16 luteal cells were not functional based on jugular progesterone (P less than or equal to 0.05) and did not respond to hCG, PGE1, or PGE2 in the presence of adenosine or PGF2 alpha (P greater than or equal to 0.05). It is concluded that adenosine enhances the response of functional luteal cells to the luteotropins hCG, PGE1 or PGE2 and adenosine reduces the luteolytic response to PGF2 alpha by hCG-stimulated ovine luteal cells in vitro.

Effects of breed, age of donor and dosage of follicle stimulating hormone on the superovulatory response of beef cows

Data were obtained on 1039 recoveries of embryos from beef cows of four breeds at two locations, in clinic and on farm. General linear models procedures were utilized to determine the effects of breed, location, age of donor, dosage of follicle stimulating hormone (FSH) and the interaction of age and FSH on the following dependent variables: 1) the mean number of ova (unfertilized oocytes and embryos) recovered; 2) the mean number and percentage of embryos (fertilized; live and dead) recovered; and 3) the mean number and percentage of transferable embryos recovered. The interaction of age of donor and dosage of FSH with breed and location prevented the pooling of data over breed and location. The mean number of ova recovered was affected by age of the donor (Charolais-in clinic), or the interaction between age of donor and dosage of FSH (Polled Hereford-in clinic and -on farm and Simmental -on farm). The mean number of embryos was affected by age of donor (Polled Hereford-in clinic), dosage of FSH (Simmental-in clinic) or their interaction (Angus-on farm). The mean number of transferable embryos was affected by age of donor (Polled Hereford-in clinic and -on farm, Simmental-in clinic and Angus-on farm). General linear models procedures were utilized to determine the effects of the embryo (stage of development and quality) and the recipient (synchrony with the donor) on the rate of pregnancy. Rate of pregnancy varied with embryo quality score and synchrony of the recipient and the embryo. In conclusion, the superovulatory response was found to be highly breed-specific, and most of the variability in embryos produced was attributed to the number of ova recovered. However, the number of ova, embryos and transferable embryos recovered was further influenced by age of the donor, dosage of FSH or their interaction.

Chronic utero-ovarian vein catheterization with subsequent occlusion prolongs the estrous cycle and changes electromyographic activity in the myometrium of ewes

The objective of our study was to determine the effect of chronic utero-ovarian vein catheterization in ewes on estrous cycle length, plasma progesterone (P) concentration, and myometrial electromyographic activity. Cyclic ewes with inferior vena cava catheters were used as controls. Estrus was synchronized in ten ewes and 10 to 12 d following estrus, the ewes were anesthetized, fitted with myometrial electromyograph leads and with utero-ovarian vein (n = 5) or inferior vena cava (n = 5) catheters. After surgery, ewes returned to estrus as expected (16 to 18 d interestrus interval). The second cycle of four of five ewes with utero-ovarian vein catheters were prolonged (40 to 58 d). The inferior vena cava catheterized ewes had normal length second cycles. Plasma P concentrations reflected the estrous cycles: low (</= 0.01 ng/ml) at estrus and 2 to 3 ng/ml at midcycle. The inferior vena cava catheterized ewes had decreased plasma P concentrations after luteolysis (Days 13 to 14) while four of five utero-ovarian vein catheterized ewes maintained elevated plasma P concentrations for 20 to 58 d. Catheterization affected the myometrial electromyograph; short events (16 to 180 sec) were increased on Days 5 to 13 in utero-ovarian vein as compared with inferior vena cava catheterized ewes (P < 0.05); long events (180 to 900 sec) tended to decrease from Days 1 to 15 in utero-ovarian vein ewes, but this was not statistically significant (P > 0.05).

Concentrations of 13, 14-dihydro-15-keto prostaglandin F2 alpha after pulsatile progesterone administration at the time of luteolysis of heifers

Progesterone was administered in pulses to 12 dairy heifers from days 17.5 to 22.5 post-estrus in order to determine its ability to modify secretion of PGF2 alpha around the time of luteolysis. Control heifers exhibited pulses of PGFM concomitant with a sharp decline in progesterone concentrations and thus these pulses were temporally associated with luteolysis. Additional pulses of PGFM were observed in heifers receiving exogenous progesterone, but these were not statistically predictable by either dose of progesterone (50 or 100 micrograms) or time of administration (3 or 6 hour intervals). However, all heifers (4/4) treated with progesterone at 3 hour intervals had additional pulses of PGFM as compared to only one heifer (1/4) treated at 6 hour intervals. When pulses of PGFM were induced by exogenous progesterone there was a substantial lag time between the initiation of progesterone treatment and their occurrence. The limited response to progesterone administration and the lack of synchrony is not consistent with an ability of exogenous progesterone to directly stimulate secretion of PGF2 alpha at the time of luteolysis.