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

Differential regulation of phospholipase A(2) activity and prostaglandin E(2) synthesis in activated and non-activated corpora lutea of lactation by the presence and absence of suckling stimulus in rats

We investigated content of prostaglandin (PG) E(2), a luteotropic eicosanoid, and phospholipase A(2) (PLA(2)) activity in two distinct states of rat corpora lutea of lactation (LCL). Rats subjected to forced weaning on day 0 postpartum (PP0) had a significant attenuation of progesterone synthesis and LCL weight on PP6 and/or PP3 compared with normally lactating rats. Repeated administration of prolactin (10 IU, twice daily) to weaned rats reversed impaired LCL function and structural development beyond the normal level of lactating animals. From PP3 to PP6, PGE(2) level in lactating LCL was increased while it was not altered in non-lactating LCL. In contrast, PLA(2) activity in the cytosol plus microsome fractions was decreased in lactating LCL and was up-regulated in non-lactating LCL as early as on PP3. This study provides the first evidence for differential regulation of PLA(2) activity and PGE(2) synthesis in activation and activation failure of postpartum CL in rats.

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.

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.

Is nitric oxide luteolytic or antiluteolytic?

Nitric oxide (NO) has been reported to be luteolytic based on treatment of cows in vivo with an inhibitor of nitric oxide synthase (NOS-produces NO), which delayed the decline in progesterone by two to three days [Jaroszewki J, Hansel, W. Intraluteal administration of a nitric oxide synthase blocker stimulates progesterone, oxytocin secretion and prolongs the life span of the bovine corpus luteum. Proc Soc Exptl Biol Med 2000;224:50-5; Skarzynski D, Jaroszewki J, Bah, M, et al. Administration of nitric oxide synthase inhibitor counteracts prostaglandin F(2alpha)-induced luteolysis in cattle. Biol Reprod 2003;68:1674-81]. The objective of this experiment was to determine the effect of a long acting NO donor or a NOS inhibitor infused chronically into the interstitial tissue of the ovarian vascular pedicle adjacent to the ovary with a corpus luteum on secretion of progesterone during the ovine estrous cycle. Ewes were treated either with Vehicle (N=5); Diethylenetriamine (DETA-control for DETA-NONOate; N=5); (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl) amino]diazen-1-ium-1,2-diolate (DETA-NONOate-long acting NO donor; N=6); or l-nitro-arginine methyl ester (l-NAME-NOS inhibitor; N=6) every 6 h from 24:00 h (0 h) on day 8 through 18:00 h on day 18 of the estrous cycle. Jugular venous blood was collected every 6h for analysis for progesterone and corpora lutea were collected at 18:00 h on day 18 and weighed. Weights of corpora lutea were heavier (P< or =0.05) in DETA-NONOate-treated ewes when compared to Vehicle, DETA, or l-NAME-treated ewes, which did not differ amongst each other (P> or =0.05). Profiles of progesterone in jugular venous blood on days 8-18 differed (P< or =0.05) in DETA-NONOate-treated ewes when compared to Vehicle, DETA, or l-NAME-treated ewes did not differ (P> or =0.05) amongst each other. It is concluded that NO is not luteolytic during the ovine estrous cycle, but may instead be antiluteolytic and prevent luteolysis.

In vivo progestin treatments inhibit nitric oxide and endothelin-1-induced bovine endometrial prostaglandin (PG) E (PGE) secretion in vitro

Synchronization of estrus with progestins in cows has been reported to inhibit nitric oxide (NO) and endothelin-1 (ET-1)-stimulated bovine luteal PGE secretion without affecting prostaglandin F2alpha (PGF2alpha) secretion in vitro [Weems YS, Randel RD, Tatman S, Lewis A, Neuendorff DA, Weems CW. Does estrous synchronization affect corpus luteum (CL) function? Prostaglandins Other Lipid Mediat 2004;74:45-59]. Two experiments were conducted to determine the effects of NO donors, endothelin-1 (ET-1), and NO synthase (NOS) inhibitors on bovine caruncular endometrial secretion of PGE and PGF2alpha in vitro. In Experiment 1, estrus was synchronized in Brahman cows with Synchromate-B ear implants, which contained the synthetic progestin norgestamet. Days 14-15 caruncular endometrial slices were weighed, diced, and incubated in vitro with treatments. Treatments (100 ng/ml) were: Vehicle (control), l-NAME (NOS inhibitor), l-NMMA (NOS inhibitor), DETA (control), DETA-NONOate (NO donor), sodium nitroprusside (NO donor), or ET-1. In Experiment 2, estrus was synchronized in Brahman cows with either Lutalyse (PGF2alpha) or a controlled intravaginal drug releasing device (CIDR-containing progesterone) or estrus was not synchronized. Days 14-15 caruncular endometrial slices were weighed, diced, and incubated in vitro with treatments. Treatments (100 ng/ml) were: vehicle, l-NAME, l-NMMA, DETA, DETA-NONOate, sodium nitroprusside, SNAP (NO donor) or ET-1. Tissues were incubated in M-199 for 1h without treatments and with treatments for 4 and 8h in both experiments. Media were analyzed for concentrations of PGE and PGF2alpha by radioimmunoassay (RIA). Hormone data in Experiments 1 and 2 were analyzed by 2x7 and 3x2x8 factorial design for ANOVA, respectively. Concentrations of PGE and PGF2alpha in media increased (P< or =0.05) from 4 to 8 h regardless of treatment group in Experiment 1, but did not differ (P> or =0.05) among treatments. In Experiment 2, concentrations of PGE and PGF2alpha increased (P< or =0.05) with time in all treatment groups of all three synchronization regimens. DETA-NONOate, SNAP, and sodium nitroprusside (NO donors) and ET-1 increased caruncular endometrial (P< or =0.05) secretion of PGE2 in unsynchronized and Lutalyse synchronized cows, but not when estrus was synchronized with a CIDR (P> or =0.05). No treatment increased (P> or =0.05) PGF2alpha in any synchronization regimen. It is concluded that norgestamet in Synchromate-B ear implants or progesterone in a CIDR alters NO or ET-1-induced secretion of PGE by bovine caruncular endometrium and could interfere with implantation by altering the PGE:PGF2alpha ratio resulting in increased embryonic losses during early pregnancy.

Effects of estrous synchronization on response to nitric oxide donors, nitric oxide synthase inhibitors, and endothelin-1 in vitro

Two experiments were conducted to determine the effects of nitric oxide (NO) donors, endothelin-(ET-1), and NO synthase (NOS) inhibitors on bovine luteal function in vitro. In experiment 1, estrus in Brahman cows was synchronized with Synchro-Mate-B (SMB) and day-13-14 corpora luteal slices were weighed, diced and incubated in vitro. Treatments (100 ng/ml) were: vehicle, N[see symbol in text]-nitro-L-arginine-L-methyl ester (L-NAME), N(G)-monomethyl-L-arginine acetate (L-NMMA), diethylenetriamine (DETA), DETA-NONOate, sodium nitroprusside (SNP), or ET-1. In experiment 2, estrus was synchronized with Lutalyse, a Controlled Intravaginal Progesterone Releasing Device (CIDR), or cows were not synchronized. Corpora lutea were collected, weighed, and luteal slices were weighed, diced and incubated in vitro with treatments. Treatments (100ng/ml) were: vehicle, L- NAME, L-NMMA, DETA, DETA-NONOate, sodium nitroprusside, S-nitroso-N-acetylpenicillamine (SNAP) or endothelin-1. Tissues were incubated in M- 199 for 1 h without treatments and for 4 and 8 h in both experiments with treatments in both experiments. Media were analyzed for progesterone, prostaglandins E2 and F2alpha (PGE2, PGF2alpha) by radioimmunoassay (RIA). Hormone data in experiments 1 and 2 were analyzed by 2 x 7 and 3 x 2 x 8 factorial design for analysis of variance (ANOVA), respectively. Luteal weights in experiment 2 were analyzed by a one-way ANOVA. Concentrations of progesterone in media were similar (P > or = 0.05) among treatments within experiments. Concentrations of PGE2 in media in experiment 1 were undetectable in 90 and 57% of the samples at 4 and 8 h, respectively. PGF2alpha increased (P < or = 0.05) with time, but did not differ (P > or = 0.05) among treatments. Secretion of PGF2alpha was not affected by treatments (P > or = 0.05). In experiment 2, luteal weights of the induced estrous cycle were decreased (P < or = 0.05) by Lutalyse. Concentrations of PGE2 and PGF2alpha increased (P < or = 0.05) with time in control of all three synchronization regimens. DETA-NONOate, SNAP, sodium nitroprusside (NO donors) and ET-1 increased (P < or = 0.05) PGE2 except in the CIDR synchronized group (P > or = 0.05). No treatment increased (P > or = 0.05) PGF2alpha in any synchronization regimen. It is concluded that either SMB containing norgestomet or a CIDR containing progesterone alters luteal secretion of PGE2, Lutalyse lowers luteal weights in the induced estrous cycle, and NO or ET-1 given alone are not luteolytic agents. It is suggested that NO and ET-1 could have indirect antiluteolytic/luteotropic effects via increasing PGE2 secretion by luteal tissue rather than being luteolytic.

Do calcium-mediated cellular signalling pathways, prostaglandin E2 (PGE2), estrogen or progesterone receptor antagonists, or bacterial endotoxins affect bovine placental function in vitro?

The major objective of this experiment was to determine whether the bovine placenta could be stimulated to secrete progesterone, since the bovine placenta secretes little progesterone when the corpus luteum is functional. Secondly, we wanted to determine whether reported abortifacients or progesterone or estrogen receptor antagonists affected bovine placental prostaglandin secretion. The ovine placenta secretes half of the circulating progesterone at day 90 of pregnancy and PGE2 appears to regulate ovine placental progesterone secretion. Calcium has been reported to regulate placental progesterone secretion in cattle. Diced 186-245-day placental slice explants from six Brahman and six Angus cows were incubated in vitro at 39.5 degrees C under 95% air: 5% CO2 at pH 7.2 in 5 ml of M-199 for 1 h in the absence of treatments and for 4 and 8 h in the presence of treatments. Treatments were: vehicle; R24571; compound 48/80; IP3; PGE2; CaCl2; cyclosporin A; lipopolysaccharide (endotoxin) from Salmonella abortus equi., enteriditis, and typhimurium; monensin; ionomycin; arachidonic acid; mimosine; palmitic acid; progesterone, androstenedione; estradiol-17beta; A23187; RU-486; or MER-25. Jugular and uterine venous plasma and culture media were analyzed for progesterone, PGE2 and PGF2alpha by radioimmunoassay (RIA). Plasma hormone data were analyzed by a One-Way Analysis of Variance (ANOVA). Hormone data in culture media were analyzed for breed and treatment effects by a Factorial Design (2 breeds, 2-range of days, 21 treatments) for ANOVA (2 x 2 x 21). Since hormone data secreted by placental tissue in vitro did not differ (P > or = 0.05) by breed or range of days of pregnancy, data were pooled and analyzed by a One-Way ANOVA. Concentrations of PGE2 in uterine venous blood were two-fold greater (P < or = 0.05) in Angus than Brahman cows. PGE2 and PGF2alpha in vehicle controls increased from 4 to 8h (P < or = 0.05), but not progesterone (P > or = 0.05) Progesterone in culture media treated with RU-486 increased (P < or = 0.05) at 4 and 8 h compared to vehicle controls and was not affected by other treatments (P > or = 0.05). Concentrations of PGE2 in media at 4 and 8 h were lower (P < or = 0.05) when compared to controls except treatment with PGE2 at 4 and 8h and RU-486 at 8h (P > or = 0.05). PGF2alpha was increased (P < or = 0.05) by RU-486 at 8h and no other treatment affected PGF2alpha at 4 or 8 h (P < or = 0.05). In conclusion, modulators of cellular calcium signalling pathways given alone do not affect bovine placental progesterone secretion at the days studied and progesterone receptor-mediated events appear to suppress placental progesterone, PGF2alpha, and PGE2 secretion in cattle. In addition, PGE2 does not appear to regulate bovine placental progesterone secretion when the corpus luteum is functional and bacterial endotoxin does not appear to affect bovine placental secretion of PGF2alpha or PGE2.

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.

Effect of mifepristone on pregnancy, pregnancy-specific protein B (PSPB), progesterone, estradiol-17beta, prostaglandin F2alpha (PGF2alpha) and prostaglandin E (PGE) in ovariectomized 90-day pregnant ewes

The objective of this experiment was to determine the effect of mifepristone, a progesterone receptor antagonist, on pregnancy and secretion of steroids, pregnancy-specific protein B (PSPB) and prostaglandins at mid-pregnancy in ewes. Ninety-day pregnant ewes were ovariectomized (OVX) and treatments were initiated 72 h post-OVX. Ewes received (1) vehicle, (2) prostaglandin F2alpha (PGF2alpha, 8 mg/58 kg/bw, i.m.) 84 h post-OVX, (3) mifepristone (50 mg intrajugular at 72, 84, 96, and 108 h post-OVX), (4) mifepristone (50mg) + PGF2alpha, (5) mifepristone (100 mg intrajugular at 72, 84, 96, and 108 h), and (6) mifepristone (100 mg) + PGF2alpha. Ewes treated with vehicle or PGF2alpha alone did not abort (P > or = 0.05). But, 60, 80, 60, and 100% of ewes treated with mifepristone (50 mg), mifepristone (50 mg) + PGF2alpha, mifepristone (100 mg), and mifepristone (100 mg) + PGF2alpha, respectively, aborted (P < or = 0.05). Profiles of progesterone, estradiol-17beta, prostaglandin E (PGE), or PSPB did not differ (P > or = 0.05) among treatment groups. Profiles of PGF2alpha of treatment groups receiving mifepristone with or without PGF2alpha differed (P < 0.05) from vehicle or PGF2alpha alone-treated ewes. It is concluded that progesterone actions are necessary to suppress uterine/placental secretion of PGF2alpha and that maintenance of critical progesterone: estradiol-17beta and PGE:PGF2alpha ratios are necessary for maintenance of pregnancy.

Effect of the aromatase inhibitor CGS-16949A on pregnancy and secretion of progesterone, estradiol-17beta, prostaglandins E and F2alpha (PGE; PGF2alpha) and pregnancy specific protein B (PSPB) in 90-day ovariectomized pregnant ewes

The aromatase inhibitor CGS-16949A was used to determine whether CGS-16949A altered secretion of progesterone, estradiol-17beta, PGE (PGE1 + PGE2), PGF2alpha and PSPB. Ninety day pregnant ewes were ovariectomized and received vehicle, PGF2alpha, CGS-16949A or PGF2alpha+CGS-16949A. None of the ewes treated with PGF2alpha, CGS-16949A or PGF2alpha+CGS-16949A aborted (P > or = 0.05) during the 108-h experimental period. Treatment with CGS-16949A lowered (P < or = 0.05) progesterone in jugular venous plasma but concentrations of progesterone were not affected (P > or = 0.05) by treatment with PGF2alpha. Concentrations of estradiol-17beta and PSPB in jugular venous plasma and PGE in inferior vena cava plasma were decreased (P < or = 0.05) by treatment with CGS-16949A. Concentrations of PGF2alpha in inferior vena cava plasma were not affected (P > or = 0.05) by treatment with CGS-16949A. Decreases in estradiol-17beta occurred before decreases in PSPB, which was then followed by decreases in PGE (P < or = 0.05). It is concluded that these data support the hypothesis that estradiol-17beta regulates placental secretion of PSPB; PSPB regulates placental secretion of PGE; and PGE regulates placental secretion of progesterone during mid-pregnancy in ewes.

Effects of indomethacin, luteinizing hormone (LH), prostaglandin E2 (PGE2), trilostane, mifepristone, ethamoxytriphetol (MER-25) on secretion of prostaglandin E (PGE), prostaglandin F2alpha (PGF2alpha) and progesterone by ovine corpora lutea of pregnancy or the estrous cycle

Two experiments were conducted to determine the luteotropin of pregnancy in sheep and to examine autocrine and paracrine roles of progesterone and estradiol-17 beta on progesterone secretion by the ovine corpus luteum (CL). Secretion of progesterone per unit mass by day-8 or day-11 CL of the estrous cycle was similar to day-90 CL of pregnancy (P > or = 0.05). In experiment 1, secretion of progesterone in vitro by slices of CL from ewes on day-8 of the estrous cycle was increased (P < or = 0.05) by LH or PGE2. Secretion of progesterone in vitro by CL slices from day-90 pregnant ewes was not affected by LH (P > or = 0.05) while PGE2 increased (P < or = 0.05) secretion of progesterone. Day 8 ovine CL of the estrous cycle did not secrete (P > or = 0.05) detectable quantities of PGF2alpha or PGE while day-90 ovine CL of pregnancy secreted PGE (P < or = 0.05) but not PGF2alpha. Secretion of progesterone and PGE in vitro by day-90 CL of pregnancy was decreased (P < or = 0.05) by indomethacin. The addition of PGE2, but not LH, in combination with indomethacin overcame the decreases in progesterone by indomethacin (P < or = 0.05). In experiment 2, secretion of progesterone in vitro by day-11 CL of the estrous cycle was increased at 4-h (P < or = 0.05) in the absence of treatments. Both day-11 CL of the estrous cycle and day-90 CL of pregnancy secreted detectable quantities of PGE and PGF2alpha (P < or = 0.05). In experiment 1, PGF2alpha secretion by day-8 CL of the estrous cycle and day-90 ovine CL of pregnancy was undetectable, but was detectable in experiment 2 by day-90 CL. Day 90 ovine CL of pregnancy also secreted more PGE than day-11 CL of the estrous cycle (P < or = 0.05), whereas day-8 CL of the estrous cycle did not secrete detectable quantities of PGE (P > or = 0.05). Trilostane, mifepristone, or MER-25 did not affect secretion of progesterone, PGE, or PGF2alpha by day- 11 CL of the estrous cycle or day-90 CL of pregnancy (P > or = 0.05). It is concluded that PGE2, not LH, is the luteotropin at day-90 of pregnancy in sheep and that progesterone does not modify the response to luteotropins. Thus, we found no evidence for an autocrine or paracrine role for progesterone or estradiol-17 36 on luteal secretion of progesterone, PGE or PGF2alpha.

Effect of PGF2alpha, indomethacin, tamoxifen, or estradiol-17beta on incidence of abortion, progesterone, and pregnancy-specific protein B (PSPB) secretion in 88- to 90-day pregnant sheep

One objective of this experiment was to evaluate our hypotheses that estradiol-17beta regulates secretion of pregnancy specific protein B (PSPB) and that secretion of progesterone during pregnancy is regulated by a prostanoid by examining the effects of prostaglandin F2alpha (PGF2alpha), a luteolyic agent; indomethacin, a prostanoid synthesis inhibitor; tamoxifen, an estrogen receptor antagonist; estradiol 17-beta; and interaction of these factors on the incidence of abortion and progesterone and PSPB secretion. Another objective was to determine if there is a luteal source of PSPB. Weights of corpora lutea were decreased (P < or = 0.05) by PGF2alpha, indomethacin, PGF2alpha + tamoxifen, PGF2alpha + indomethacin, and PGF2alpha + estradiol-17beta but not (P > or = 0.05) by tamoxifen or estradiol-17beta alone. No ewe treated with PGF2alpha alone aborted (P > or = 0.05). Forty percent of ewes treated with PGF2alpha + estradiol-17beta aborted (P < or = 0.05), but ewes were not aborted by any other treatment within the 72-h sampling period. Profiles of progesterone in jugular venous blood differed (P < or = 0.05) among control, indomethacin-, tamoxifen-, and PGF2alpha + indomethacin-treated ewes. Progesterone in jugular venous blood of control ewes decreased (P < or = 0.05) by 24 h, followed by a quadratic increase (P < or = 0.05) from 24 to 62 h. Progesterone in jugular venous blood of indomethacin-, PGF2alpha-, PGF2alpha- + tamoxifen-, PGF2alpha + indomethacin-, PGF2alpha + estradiol-17beta-, and tamoxifen-treated ewes was reduced (P < or = 0.05) by 18 h and did not vary (P > or = 0.05) for the remainder of the 72-h sampling period. Progesterone in vena cava and in uterine venous blood was reduced (P < or = 0.05) at 72 h in PGF2alpha-, indomethacin-, tamoxifen-, PGF2alpha + indomethacin-, PGF2alpha + tamoxifen-, and PGF2alpha + estradiol-17beta-treated ewes. Weights of placentomes did not differ among treatment groups (P > or = 0.05). Profiles of PSPB in inferior vena cava blood differed (P < or = 0.05) among control, estradiol-17beta-, indomethacin-, tamoxifen-, PGF2alpha + indomethacin-, and PGF2alpha + tamoxifen-treated 88- to 90-day pregnant ewes. Concentrations of PSPB in inferior vena cava blood were increased (P < or = 0.05) in indomethacin-, estradiol-17beta-, tamoxifen-, PGF2alpha + tamoxifen-, and PGF2alpha + indomethacin-treated 88- to 90-day pregnant ewes within 6 h and did not vary (P > or = 0.05) for the remainder of the 72-h sampling period. Concentrations of PSPB in uterine venous blood of indomethacin-, tamoxifen-, PGF2alpha + tamoxifen-, and PGF2alpha + indomethacin-treated ewes were greater (P < or = 0.05) at 72 h than at 0 h. PSPB in ovarian venous blood did not differ (P > or = 0.05) adjacent or opposite to the ovary with the corpus luteum. It is concluded from these data that estrogen regulates placental secretion of PSPB and that a prostanoid, presumably prostaglandin E, regulates placental secretion of progesterone during 88-90 days of gestation in sheep and that there is no luteal source of PSPB.

Effect of prostaglandin F2alpha (PGF2alpha), indomethacin, tamoxifen or estradiol-17beta on prostaglandin E (PGE), PGF2alpha and estradiol-17beta secretion in 88 to 90-day pregnant sheep

Treatment with PGF2alpha plus estradiol-17beta aborts 90-day pregnant ewes, whereas PGF2alpha or estradiol-17beta alone does not abort ewes. The objective of this experiment was to evaluate whether tamoxifen, an estrogen receptor antagonist, estradiol-17beta, prostaglandin F2alpha (PGF2alpha), indomethacin, or some of their interactions affected ovine uterine/placental secretion of PGF2alpha, estradiol-17beta or prostaglandins E (PGE), because a single treatment with PGF2alpha and estradiol-17beta given every 6 h aborts 90-day pregnant ewes. Concentrations of PGF2alpha in uterine venous blood were increased (P < or = 0.05) by estradiol-17beta, PGF2alpha + estradiol-17beta, and PGF2alpha + tamoxifen, and decreased (P < or = 0.05) by indomethacin or PGF2alpha + indomethacin at 72 h when compared to the 0 h samples. Concentrations of PGE in uterine venous blood were decreased (P < or = 0.05) by indomethacin and PGF2alpha + indomethacin and increased (P < or = 0.05) by PGF2alpha + estradiol-17beta at 72 h when compared to the 0 h samples. Concentrations of PGF2alpha in inferior vena cava blood at 6 h were increased (P < or = 0.05) by PGF2alpha either alone or in combination with indomethacin, tamoxifen, or estradiol-17beta, which is due to the PGF2alpha injected. Concentrations of PGF2alpha in inferior vena cava blood in PGF2alpha + estradiol-17beta-treated 88- to 90-day pregnant ewes increased (P < or = 0.05) linearly over the 72-h sampling period and averaged 4.0 + 0.4 ng/ml. Concentrations of PGF2alpha in inferior vena cava blood of control, PGF2alpha, tamoxifen, PGF2alpha + indomethacin, PGF2alpha + tamoxifen, and estradiol-17beta-treated ewes did not differ (P > or = 0.05) and averaged 0.4 + 0.04 ng/ml. Profiles of PGE in inferior vena cava blood of 88- to 90-day pregnant ewes treated with vehicle, PGF2alpha, estradiol-17beta, tamoxifen, tamoxifen + PGF2alpha, or estradiol-17beta + PGF2alpha did not differ (P > or = 0.05). Concentrations of PGE in inferior vena cava blood of 88- to 90-day pregnant ewes treated with indomethacin or PGF2alpha + indomethacin were lower (P < or = 0.05) than in control ewes. Concentrations of estradiol-17beta in jugular venous plasma of PGF2alpha + estradiol-17beta-treated 88- to 90-day pregnant ewes increased linearly and differed (P < or = 0.05) from controls. Profiles of estradiol-17beta in jugular venous plasma of PGF2alpha, indomethacin, tamoxifen, and PGF2alpha + tamoxifen and PGF2alpha + indomethacin, estradiol-17beta, and controls did not differ (P > or = 0.05). It is concluded that treatment with a single injection of PGF2alpha and estradiol-17beta given every 6 h causes a linear increase in PGF2alpha and estradiol-17beta.

Secretion of progesterone, estradiol-17beta, PGE, PGF2alpha, and pregnancy-specific protein B by 90-day intact and ovariectomized pregnant ewes

Ninety-day pregnant ewes were either laparotomized, ovaries left in situ or bilaterally ovariectomized, and a jugular venous catheter and an inferior vena cava catheter via the saphenous vein were installed. Seven days later, placenta slices were collected and incubated in vitro for 4 h. Secretions of progesterone, PGE, estradiol-17beta and pregnancy-specific protein B (PSPB) in vitro by placenta from ovariectomized ewes were increased (P < or = 0.05) by 2.7-, 3.6-, 2.2-, and 2.4-fold, respectively, when compared to placenta slices from intact 90-day pregnant ewes. Secretion of PGF2alpha in vitro was unchanged (P > or = 0.05). Ovariectomy decreased (P < or = 0.05) jugular venous progesterone for 78 h followed by a quadratic increase (P < or = 0.05), whereas progesterone remained unchanged (P > or = 0.05) in intact ewes over the 162-h sampling period. Ovariectomy increased (P < or = 0.05) PGE in inferior vena cava plasma over the last half of the 162-h sampling period, whereas concentration of PGF2alpha did not change (P > or = 0.05). Increases in PGE occurred before the increase in progesterone. Concentrations of PSPB in inferior vena cava plasma of ovariectomized pregnant ewes increased (P < or = 0.05) during the last half of the 162-h sampling period, but not in intact ewes (P > or = 0.05). PSPB increased before PGE and progesterone. Concentrations of estradiol-17beta in jugular venous plasma of ovariectomized pregnant ewes increased (P < or = 0.05) during the last half of the sampling period, but not in intact ewes (P > or = 0.05). Increases in estradiol-17beta occurred before increases in PSPB. It is concluded that these data support the hypothesis that estradiol-17beta may control placental secretion of PSPB; PSPB may regulate placental secretion of PGE; and PGE may regulate placental secretion of progesterone.

Effect of trilostane on PGE, PGF2alpha, estradiol-17beta, and progesterone secretion and pregnancy of 90-day ovariectomized pregnant ewes

Ninety-day pregnant sheep were ovariectomized and received vehicle or trilostane every 12 h through 132 h, starting at 72 h postovariectomy. All trilostane-treated ewes aborted (P < or = 0.05) between 36 and 50 h after initiation of treatment. Profiles of progesterone in jugular venous blood differed (P < or = 0.05) and was lower (P < or = 0.05) in trilostane-treated ewes. Profiles of estradiol-17beta in jugular venous plasma of trilostane-treated ewes differed (P < or = 0.05) from controls. Estradiol-17beta increased after the first two treatments, followed by a return 2 h later to pretreatment levels (P > or = 0.05), which was followed by a sustained increase (P < or = 0.05) in estradiol-17beta. Profiles of PGF2alpha in inferior vena cava plasma of trilostane-treated ewes differed and were greater (P < or = 0.05) and occurred with the sustained increase in estradiol-17beta and the onset of most of the abortions. Profiles of PGE in inferior vena cava plasma between control and trilostane-treated 90-day pregnant ewes did not differ (P > or = 0.05). It is concluded that abortions occur at midpregnancy in sheep when the estradiol-17beta : progesterone ratio changes sufficiently to cause a sustained increase in estradiol-17beta and PGF2alpha but without changing placental secretion of PGE.

Trilostane but not prostaglandin F2alpha (PGF2alpha) or cortisol aborts 90-day-pregnant lutectomized sheep

Ewes were lutectomized and treatments were started 72 h later. Pregnant ewes were treated with vehicle; prostaglandin F2alpha (PGF2alpha); cortisol (C); trilostane (TR), a 3beta-hydroxy-steroid dehydrogenase inhibitor; PGF2alpha + C; TR + PGF2alpha; TR + C, or TR + PGF2 + C. TR, TR + PGF2alpha, TR + C, and TR + PGF2alpha + C aborted (P < or = 0.05) all ewes receiving TR. One ewe treated with PGF2alpha aborted (P > or = 0.05). The average time to abortion of TR-treated ewes was 50.8 h (P < or = 0.05) after initiation of treatments. All aborted ewes had retained placentas (P < or = 0.05) except one ewe in the TR + PGF2alpha, treatment group. TR was given every 12 h starting at 72 h postlutectomy until 96 h postlutectomy. TR reduced (P < or = 0.05) progesterone. Estradiol-17beta was increased (P < or = 0.05) 2 h after the first two TR treatments and declined 2 h later and was followed by a sustained increase (P < or = 0.05) in estradiol-17beta, which was coincident with the onset of abortions. Estradiol-17beta was increased (P < or = 0.05) by PGF2alpha but did not decrease (P > or = 0.05) placental secretion of progesterone. It is concluded that TR but not PGF2alpha is an abortifacient in 90-day-pregnant lutectomized ewes and that abortion occurs only when there is a decrease in circulating progesterone and an increase in circulating estradiol-17beta.

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.

Effects of luteinizing hormone (LH), PGE2, 8-Epi-PGE1, 8-Epi-PGF2 alpha, trichosanthin and pregnancy specific protein B (PSPB) on secretion of prostaglandin (PG) E (PGE) or F2 alpha (PGF2 alpha) in vitro by corpora lutea (CL) from nonpregnant and pregnant cows

Both Day 14 corpora lutea (CL) of the estrous cycle and Day 200 CL of pregnancy secrete detectable prostaglandin E (PGE) and prostaglandin F2 alpha (PGF2 alpha) in vitro. Corpora lutea from Day 200 pregnant cows secrete more PGE and PGF alpha in vitro than Day 14 CL of the estrous cycle when incubated in control medium without treatments (p < or = 0.05). In addition, secretion of both PGE and PGF2 alpha in vitro by both Day 200 CL of pregnancy and Day 14 of the estrous cycle increase (p < or = 0.05) with time in culture in the absence of treatments. The PGE:PGF2 alpha ratio secreted at 4 h in the absence of treatments by Day 14 CL of the estrous cycle was 1.2 and at 8 h was 1.0 and did not differ (p > or = 0.05), while the PGE:PGF2 alpha ratio secreted by 200 day CL of pregnancy in the absence of treatments at 4 h was 0.8 and at 8 h decreased (p < or = 0.05) to 0.4. The PGE:PGF2 alpha ratio at 8 h by 200 day CL of pregnancy was lower (p < or = 0.05) than in the Day 14 CL of the estrous cycle at 4 or 8 h. Secretion of PGE or PGF2 alpha was affected by luteinizing hormone, PGE2, 8-Epi-PGE1, 8-Epi-PGE2, trichosanthin, and pregnancy specific protein B (PSPB) and was time and dose dependent (p < or = 0.05). In summary, the altered ratio of PGE:PGF2 alpha may explain the decreased secretion of progesterone at 8 h by Day 200 CL of pregnancy reported previously from the same samples. In addition, caution should be exercised in interpretation of progesterone secretion data with bovine CL studies in vitro. Also, PSPB may play an indirect role through PGE to regulate bovine luteal secretion of progesterone.

Effect of luteinizing hormone (LH), PGE2, 8-EPI-PGE1, 8-EPI-PGE2, trichosanthin, and pregnancy specific protein B (PSPB) on secretion of progesterone in vitro by corpora lutea (CL) from nonpregnant and pregnant cows

Secretion of progesterone by Day 14 bovine corpora lutea (CL) of the estrous cycle and Day 200 CL of pregnancy was evaluated in vitro to determine what regulates secretion of progesterone by CL of pregnancy. Weights of Day 200 CL of pregnancy (4356 +/- 223 g) were heavier when compared to Day 14 CL of the estrous cycle of Brahman cows (3643 +/- 128 g; p < or = 0.05); however, both Day 14 and Day 200 minced CL slices secreted similar basal amounts of progesterone per unit mass (p > or = 0.05). Secretion of progesterone in vitro by Day 14 CL of the estrous cycle was increased at 4 and 8 h (p < or = 0.05) by 10 or 100 ng/mL luteinizing hormone (LH) and did not differ between doses (p > or = 0.05). Progesterone secretion in vitro by Day 200 CL of pregnancy was not increased (p > or = 0.05) by LH at 4 or 8 h. However, progesterone secretion in vitro by Day 14 CL of the estrous cycle or Day 200 CL of pregnancy was increased (p < or = 0.05) at 4 h by 10 or 100 ng/mL PGE2, which did not differ by dose or reproductive status (p > or = 0.05). At 8 h, Day 14 CL of the estrous cycle secretion of progesterone in vitro was increased (p < or = 0.05) by both doses of PGE2 but only at 8 h by 100 ng/mL from Day 200 CL of pregnancy (p < or = 0.05). Secretion of progesterone in vitro was not affected (p > or = 0.05) by 10 or 100 ng/mL 8-Epi-PGE1 or 8-Epi-PGE2 at 4 or 8 h from Day 14 CL of the estrous cycle or Day 200 of pregnancy. Trichosanthin increased (p < or = 0.05) secretion of progesterone in vitro by 10 ng/mL at 4 h and at 8 h by Day 14 CL of the estrous cycle or at 8 h by Day 200 CL of pregnancy but trichosanthin at 100 ng/mL did not affect (p > or = 0.05) secretion of progesterone in vitro by Day 14 CL of the estrous cycle or Day 200 CL of pregnancy at 4 or 8 h. Pregnancy specific protein B (PSPB) increased (p < or = 0.05) secretion of progesterone in vitro at 4 and 8 h by Day 14 CL of the estrous cycle and did not differ between incubation times (p > or = 0.05). PSPB increased secretion of progesterone at 4 h but not at 8 h (p > or = 0.05) by Day 200 CL of pregnancy. These data suggest that PGE2 or PSPB but not LH, 8-Epi-PGE1 or 8-Epi-PGE2 regulates luteal secretion of progesterone by bovine CL at mid-pregnancy. In addition, it is suggested that weights of bovine CL of pregnancy increase to compensate for a lack of placental secretion of progesterone.

Production of prostaglandin F2 alpha and E2 in explants of intrauterine tissues of guinea pigs during late pregnancy and labor

Prostaglandin production in amnion and decidua is considered important for human parturition. We investigated in pregnant guinea pigs, a species similar to women in regard to the endocrinology of pregnancy, whether the production rates of PGE2 and PGF2 alpha in various intrauterine tissues are compatible with a role in parturition. Net production rates were measured at 45, 55 and 65 days of gestation and during labor in amnion, chorion, myo-endometrium, the outer layer of the myometrium, the site of placental implantation, and placenta. Net production rates in amnion increased between 45 days and labor (30-fold for PGE2 and 8-fold for PGF2 alpha, P < 0.0001). During labor, the production rates in amnion of PGE2 (P = 0.006) and PGF2 alpha (P = 0.019) were higher than at 45, 55, and 65 days of gestation. In myo-endometrium, the production rates of PGF2 alpha were higher at 65 days of gestation than at 55 days and during labor (P = 0.046). Addition of arachidonic acid (10(-5) M) increased production of PGE2 and/or PGF2 alpha in all tissues (P < 0.05) except placenta. In amnion, the response to arachidonic acid increased with advancing gestation. This suggests that 1) PGE2 and PGF2 alpha produced by amnion have a potential role in the initiation and maintenance of labor, 2) PGF2 alpha produced by myo-endometrium has a potential role in the initiation of labor, 3) cyclooxygenase(s) are not rate-limiting except in placenta, and 4) the expression of cyclooxygenase in amnion increases with advancing gestation.

Exogenous prostaglandin F2 alpha stimulates utero-ovarian release of prostaglandin F2 alpha in sheep: a possible component of the luteolytic mechanism of action of exogenous prostaglandin F2 alpha

Exogenous prostaglandin F2 alpha (PGF2 alpha) is luteolytic in sheep, but its mechanism of action is not completely understood. We hypothesized that exogenous PGF2 alpha stimulates the uterine and(or) ovarian secretion of PGF2 alpha and that, when intramuscular doses of PGF2 alpha are minimal, the utero-ovarian unit is a component of the luteolytic mechanism of action of exogenous PGF2 alpha. Thus, this study was conducted to determine whether exogenous PGF2 alpha stimulates the utero-ovarian release of PGF2 alpha. Catheters were positioned in the vena cava at points cranial and caudal to the entry of utero-ovarian blood, and ewes were either hysterectomized and ovariectomized (H/OX) or left intact (Intact). Treatments were in a 2 x 2 factorial arrangement (i.e., H/OX and PGF2 alpha were the main effects), and there were five ewes per treatment group. In Experiment 1, on Day 9 after the onset of estrus, either saline or PGF2 alpha (15 mg) was injected intramuscularly in the neck, and vena caval blood samples were collected frequently for 120 min, then less frequently for 48 hr. In Experiment 2, on Day 9 after estrus or H/OX, either saline of PGF2 alpha (5 mg, then 5 mg 3 hr later) was injected intramuscularly in the neck, and vena caval blood samples were collected frequently for 150 min after each injection. In both experiments, exogenous PGF2 alpha induced immediate and significant increases in the utero-ovarian release of PGF2 alpha. The increases in PGF2 alpha concentrations were considerably more pronounced in vena caval blood samples collected cranial than in those collected caudal to the entry of utero-ovarian blood, and the increase was significantly greater in Intact than in H/OX ewes treated with PGF2 alpha. Vena caval concentrations of 13,14-dihydro-15-keto-PGF2 alpha (PGFM) increased after exogenous PGF2 alpha, but the changes in PGFM were not suitable representations of the changes in vena caval concentrations of PGF2 alpha. Changes in progesterone concentrations indicated that both PGF2 alpha injection regimens were luteolytic. The results from this study indicate that exogenous PGF2 alpha stimulates the utero-ovarian production of PGF2 alpha, and we believe that the utero-ovarian unit is a component of the luteolytic mechanism of action of exogenous PGF2 alpha.

Prostaglandin F2 alpha, progesterone and oxytocin production by cultured bovine luteal cells treated with prostaglandin E2 and pregnancy-specific protein B

The objectives of this experiment were to study the effects of pregnancy-specific protein B (PSPB) and prostaglandin E2 (PGE2) on bovine luteal cell progesterone (P4), prostaglandin F2 alpha (PGF2 alpha) and oxytocin production. Corpora lutea were collected during the mid- (days 10-12; n = 5) or late-luteal (days 17-18; n = 5) stages of the estrous cycle. Luteal cells were dispersed and accessory cells removed. Luteal cells (1.5 x 10(5)) were incubated in a 3 x 3 factorial arrangement and treated with PSPB (0, 2.5, or 5.0 micrograms) and PGE2 (0, 100, or 200 ng) in 500 microL of Ham's F-12 medium. All cells were incubated for 18 h before adding treatments. Samples were then collected at 6 h and 12 h. During the 18 h pretreatment period, P4, PGF2 alpha, and oxytocin production was similar between the prospective treatment groups. The PSPB failed to increase P4 production. The PGE2 x time interaction showed that P4 increased in response to PGE2 treatment at 6 h (P < 0.001) and 12 h (P < 0.03). Also, the stage x time interaction indicated that mid-stage cells produced more (P < .001) P4 than late-stage cells during the pretreatment period at 6 h and 12 h. The PSPB did not alter PGF2 alpha production by mid-stage cells, but increased (P < .05) PGF2 alpha by late-stage cells. Also, PGE2 stimulated (P < 0.001) PGF2 alpha secretion by both mid- and late-stage cells; luteal cells treated with 200 ng of PGE2 produced more (P < 0.001) PGF2 alpha than 100 ng of PGE2. Oxytocin secretion was not changed by treatment with PGE2 or PSPB. Oxytocin production was greater (P < 0.001) by mid-stage than late-stage cells during the pretreatment period at 6 h and 12 h. Oxytocin production was similar between the 6 h and 12 h culture times within stage of the cycle. These data indicate that PSPB does not change bovine luteal cell P4 or oxytocin production, but elevates PGF2 alpha in late-stage cells. The PGE2 increases both P4 and PGF2 alpha, but does not alter oxytocin production. Lastly, PSPB and PGE2 do not interact to promote P4 PGF2 alpha, or oxytocin production by cultured bovine luteal cells.

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.

Prostaglandins and sex steroids from corpora lutea of pregnant mares. In vitro studies

To delineate endocrine mechanisms regulating equine luteal function and the possible functional differences between one month and three month corpora lutea of pregnancy (CL), the in vitro basal releases of prostaglandin F (PGF), prostaglandin E2 (PGE2), progesterone, and 17 beta-estradiol by one and three month CL of pregnant mares were evaluated. In addition, the in vitro effects of PGF2 alpha PGE2, progesterone and 17 beta-estradiol on synthesis of prostaglandins (PGs) and sex steroids were studied. PGF, PGE2, and 17 beta-estradiol secretion was higher in one month than in three month CL, while progesterone was secreted similarly by both types of CL. PGE2 treatment decreased 17 beta-estradiol in one month CL; progesterone increased PGE2 in one and three month CL; 17 beta-estradiol increased PGE2 in one month CL. This study suggests that, in one month CL, PGE2 production could be regulated by progesterone and 17 beta-estradiol, while, in three month CL, this prostaglandin seems to be under the control of progesterone alone.

Effects of prostaglandin F2 alpha (PGF2 alpha) on secretion of estradiol-17 beta and cortisol in 90 to 100 day hysterectomized, intact and ovariectomized pregnant ewes

Vehicle or 8 or 16 mg PGF2 alpha/58 kg/body weight (BW) was given intramuscularly to intact, hysterectomized and ovariectomized 90 to 100 day pregnant ewes in three separate experiments. Hysterectomy alone decreased (P < or = 0.05) estradiol-17 beta in jugular venous blood by 80 percent within 16 hours and profiles of estradiol-17 beta did not differ (P > or = 0.05) among vehicle or 8 or 16 mg PGF2 alpha/58 kg/BW-treated ewes. Profiles of estradiol-17 beta differed (P < or = 0.05) in intact pregnant ewes treated with 8 or 16 mg PGF2 alpha/58 kg/BW when compared to controls and in ovariectomized (P < or = 0.10) 90 to 100 day pregnant ewes treated with 16 mg PGF2/58 kg/BW. Estradiol-17 beta decreased (P < or = 0.05) over time in vehicle and 8 mg PGF2 alpha/58 kg/BW-treated intact and in vehicle-treated ovariectomized 90 to 100 day pregnant ewes. Cortisol decreased (P < or = 0.05) over time in hysterectomized, intact, and ovariectomized 90 to 100 days pregnant ewes, but did not differ (P < or = 0.05) among vehicle or 8 or 16 mg PGF2 alpha/58 kg/BW-treated ewes. It is suggested that estradiol-17 beta has a role in regulating ovine placental steroidogenesis.

Noradrenaline affects secretory function of corpus luteum independently on prostaglandins in conscious cattle

The aim of this study was to examine whether prostaglandins are involved in the effects of noradrenaline on corpus luteum (CL) function. To establish an effective dose of indomethacin (INDO) to prevent prostaglandin synthesis, different doses (120, 180, 240 and 300 mg) of drug were infused for 30 min on days 17-18 of the estrous cycle in four heifers and followed with 50 IU of OT. Plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) were measured, both to illustrate the concentrations of all prostaglandins and to establish the effective dose of INDO that can effectively block prostaglandins synthesis. In Experiment 2, on days 10-12 of the cycle, heifers (n = 6) were infused in a Latin square design with 4 mg of noradrenaline (NA) and pre-treated with 120 mg of INDO or with saline. In both cases, NA did stimulate progesterone and ovarian oxytocin secretion. We conclude that NA affects secretory function of the CL independently of prostaglandins.

Serum progesterone and luteinizing hormone in ewes treated with PGF 2 alpha during mid-gestation and gonadotropin releasing hormone after parturition

Two studies were conducted to determine if postpartum (PP) reproductive function could be enhanced in ewes by PGF2 alpha during mid-gestation (Trial 1) and GnRH within 10 days PP (Trial 2). Trial 1 utilized 31 ewes (mean body weight = 84 kg) assigned to two treatment groups to receive (I.M.) either saline (control, n = 17) or PGF2 alpha (0.14 mg/kg body weight, n = 14) on day 74 of gestation. Results from the first study indicated success in regressing the corpus luteum (CL) of pregnancy as indicated by decreased serum progesterone (P4, P < 0.05) by 24 hours after treatment. In addition, by 20 days after treatment, serum luteinizing hormone (LH) concentrations in treated ewes were higher (P < 0.01) than in controls. However, ovarian activity was not re-established by 30 days PP in this study. In Trial 2, 35 ewes (mean body weight = 79 kg) were randomly assigned to one of four groups: no treatment (controls, n = 9), PGF2 alpha (no GnRH, n = 9), GnRH (no PGF2 alpha n = 9) or both PGF2 alpha and GnRH (n = 9). The PGF2 alpha-treated animals received 0.14 mg PGF2 alpha/kg body weight (I.M.) on day 73 of gestation and GnRH-treated ewes received 50 micrograms GnRH (I.M.) on days 2, 6, and 10 PP. As in Trial 1, P4 concentrations in PGF2 alpha-treated ewes were lower (P < 0.02) than in control ewes by 24 hours after treatment. Progesterone remained lower in PGF2 alpha-treated animals through day 116 of gestation. However, no differences were detected (P > 0.65) in LH concentrations between the two groups in this same period. Likewise, no differences were observed (P > 0.32) in LH concentrations between the PGF2 alpha-treated and control ewes on days 2, 6, and 10 PP. However, elevated (P < 0.07) LH concentrations were noted in ewes receiving 50 micrograms GnRH compared with ewes not receiving GnRH. In addition, area under the LH curve (AUC) was greater (P < 0.01) for GnRH-treated animals on days 2, 6, and 10 PP and LH AUC increased over the PP period in GnRH-treated ewes. Three of eight ewes receiving both PGF2 alpha and GnRH treatments had ovarian activity within 30 days PP as indicated by P4 concentrations above 1 ng/ml while no other ewes had ovarian activity during this time period.