Receptors for prostaglandins F2 alpha and E2 in ovine corpora lutea during maternal recognition of pregnancy.

Plasma membrane receptors for prostaglandins (PG) F2 alpha and E2 were quantified in ovine corpora lutea obtained from nonpregnant and pregnant ewes on Days 10, 13, and 15 post-estrus, and from additional ewes on Days 25 and 40 of pregnancy. Regardless of reproductive status or day post-estrus, concentrations of luteal receptors for PGF2 alpha were 7- to 10-fold greater than those for PGE2. In pregnant ewes the concentration of receptors for PGF2 alpha was highest on Day 10 (35.4 +/- 2.8 fmol/mg) and lowest on Day 25 (22.3 +/- 2.5 fmol/mg). A difference in the concentration of luteal receptors for PGF2 alpha between pregnant and nonpregnant ewes was apparent only on Day 15 post-estrus, at which time the concentration of receptors for PGF2 alpha was higher in pregnant ewes than in nonpregnant ewes (27.1 +/- 2.7 vs. 17.7 +/- 2.7 fmol/mg). Concentrations of receptors for PGE2 in pregnant ewes were similar (p > 0.05; 2.8 +/- 0.3 to 3.7 +/- 0.2 fmol/mg) between Days 13 and 40 but were higher (p < 0.05) than in corpora lutea obtained from nonpregnant ewes on Days 10 (5.0 +/- 0.4 vs. 4.1 +/- 0.2 fmol/mg) and 15 (3.7 +/- 0.2 vs. 2.0 +/- 0.4 fmol/mg) post-estrus. Although concentrations of receptors for both PGF2 alpha and PGE2 were lowest in corpora lutea obtained from nonpregnant ewes on Day 15, this was not due to luteal regression since the weights and concentrations of progesterone in corpora lutea on Day 15 were not lower than those for corpora lutea obtained on Days 10 and 13.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of hysterectomy and uterine decidualization on in vivo levels of prostaglandins in the corpus luteum of adult pseudopregnant rats

A possible role of the uterus in regulating content of luteal prostaglandins (PGs) was investigated. Pseudopregnancy was induced in adult virgin female rats by mating them with vasectomized male rats. On Day 5 of pseudopregnancy, decidualization of the uterus was induced or hysterectomy was performed. As controls, intact pseudopregnant animals with a luteal phase of 13 +/- 1 days were used. Measurements of in vivo tissue levels of PGF2 alpha, PGE2, and 6-keto-PGF1 alpha were performed by RIA after homogenization and extraction procedures in CL of pseudopregnancy and remainder of ovaries on Days 5, 13, and 19. Serum levels of progesterone and 20 alpha-dihydroprogesterone were determined by RIA. In hysterectomized animals, PGF2 alpha levels increased 2.5-fold in corpora lutea on Day 13 compared with levels on Day 5 of pseudopregnancy, but were still lower than in control rats undergoing functional luteolysis on Day 13. Decidual-tissue-bearing rats exhibited low levels of PGF2 alpha on Day 13 of pseudopregnancy. On Day 19, when luteolysis had occurred in decidual-tissue-bearing and hysterectomized rats, as judged by plasma levels of progestins, luteal content of PGF2 alpha was elevated to a similar level as that in control animals undergoing functional luteolysis on Day 13. When data pooled from control, decidual-tissue-bearing and hysterectomized rats were analyzed, a highly significant inverse correlation (r = -0.72, n = 46, p less than 0.001) between luteal PGF2 alpha content and ratio of plasma progestins was found.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prostaglandin F2 alpha-induced release of oxytocin from bovine corpora lutea in vitro

Two experiments were conducted to study the in vitro effects of prostaglandins F2 alpha (PGF2 alpha), E2 (PGE2), and luteinizing hormone (LH) on oxytocin (OT) release from bovine luteal tissue. Luteal concentration of OT at different stages of the estrous cycle was also determined. In Experiment 1, sixteen beef heifers were assigned randomly in equal numbers (N = 4) to be killed on Days 4, 8, 12, and 16 of the estrous cycle (Day 0 = day of estrus). Corpora lutea were collected, an aliquot of each was removed for determination of initial OT concentration, and the remainder was sliced and incubated with vehicle (control) or with PGF2 alpha (10 ng/ml), PGE2 (10 ng/ml), or LH (5 ng/ml). Luteal tissue from heifers on Day 4 was sufficient only for determination of initial OT levels. Luteal OT concentrations (ng/g) increased from 414 +/- 84 on Day 4 to 2019 +/- 330 on Day 8 and then declined to 589 +/- 101 on Day 12 and 81 +/- 5 on Day 16. Prostaglandin F2 alpha induced a significant in vitro release of luteal OT (ng.g-1.2h-1) on Day 8 (2257 +/- 167 vs. control 1702 +/- 126) but not on Days 12 or 16 of the cycle. Prostaglandin E2 and LH did not affect OT release at any stage of the cycle studied. In Experiment 2, six heifers were used to investigate the in vitro dose-response relationship of 10, 20, and 40 ng PGF2 alpha/ml of medium on OT release from Day 8 luteal tissue.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prostaglandin F in reproductive tissues collected during the luteal phase of the estrous cycle and at parturition in Virginia opossums (Didelphis virginiana )

Prostaglandin F(2alpha) (PGF(2alpha)) plays a role in the regression of the corpus luteum (CL) in a number of placental mammals. However, the mechanism of luteal regression has not been extensively studied in marsupials. The objectives of this study were to characterize changes in concentrations of PGF(2alpha) within utero-ovarian (UO) tissue/venous plasma during the luteal phase of the estrous cycle in Virginia opossums, to correlate these changes with those of plasma progesterone (P(4)), and to characterize the peripheral pattern of 13,14-dihydro-15-keto-PGF(2alpha) (PGFM) in parturient opossums. Ovaries, uteri, UO venous plasma and peripheral plasma were collected on Days 5, 9 and 12 after induced ovulation (n = 3 to 4 opossums/group). In addition, concentrations of PGFM were measured in peripheral plasma collected from two opossums during late gestation (Days 7,9,11 and 12) and at parturition (Day 13). Concentrations of P(4), PGFM and PGF(2alpha) in tissue homogenates and plasma samples were estimated by radioimmunoassay. In nonpregnant opossums, peripheral P(4) levels were highest on Day 5 (38.8 +/- 11.1 ng/ml, x +/- SEM) declined on Day 9 (22.6 +/- 7.4 ng/ml), and were at basal levels by Day 12 (2.4 +/- 0.7 ng/ml). Endometrial concentrations of PGF(2alpha) increased (P = 0.056) from Day 5 (15.7 +/- 4.1 ng/g) to Day 9 (92.1 +/- 61.0 ng/g) and were maintained to Day 12 (97.2 +/- 25.7 ng/g). Prostaglandin F(2alpha) concentrations in UO plasma increased (P < 0.01) from Day 5 (143.1 +/- 32.7 pg/ml) to Day 12 (333.0 +/- 32.4 pg/ml). Prostaglandin F(2alpha) concentrations in ovarian tissue followed a similar pattern and were correlated with UO concentrations (r = 0.708, P < 0.05). In pregnant opossums, the highest levels of peripheral PGFM were recorded in the peripartum period, when luteal regression would also be expected to occur. The negative temporal relationship between peripheral concentrations of P(4) and concentrations of PGF(2alpha) in UO tissue/venous plasma observed in this preliminary study is consistent with the notion that PGF(2alpha) from the ovary and/or uterus may play a role in CL regression in the opossum.     

Changes in corpus luteum content of prostaglandin F2 alpha and E in the adult pseudopregnant rat

Conflicting reports exist regarding the source of luteolytic PGF2 alpha in the rat ovary. To assess the quantities of different PGs, measurements of PGF2 alpha, PGE and PGB were performed by radioimmunoassay in the adult pseudopregnant rat ovary throughout the luteal lifespan. Ovaries of 84 rats were separated by dissection into two compartments, corpora lutea of pseudopregnancy and remainder of ovary. Tissue samples were homogenized and prostaglandins extracted and determined by radioimmunoassay. During the mid-luteal and late-luteal phases, levels of PGs were significantly higher in the corpora lutea of pseudopregnancy than in the remainder of ovary. An increase of PGF2 alpha-content in the corpus luteum was registered with peak-levels of 53.9 +/- 8.5 (mean +/- SEM, N = 18) ng/g tissue wet weight at day 13 of pseudopregnancy. PGE-levels reached peak-values at day 11 of pseudopregnancy (271.6 +/- 28.4 ng/g w w, mean +/- SEM, N = 12). PGB-levels were below detection limits in all compartments for all ages studied. The present study demonstrates increased availability of PGF2 alpha in the corpus luteum during the luteolytic period, and points toward either increased luteal synthesis or luteal binding of PGF2 alpha during the luteolytic period.     

Synthesis of prostaglandin F2 alpha, E2 and prostacyclin in isolated corpora lutea of adult pseudopregnant rats throughout the luteal life-span.

The ability of de novo biosynthesis of prostaglandins (PGs) in individual whole corpora lutea (CL) obtained from sterile-mated adult pseudopregnant rats on different days of the luteal phase and the post-luteolytic period was evaluated. Production of PGs, progesterone and 20 alpha-dihydroprogesterone were determined after in vitro incubation of CL extirpated from Day 2 to Day 19 after mating. A time-relationship with increased accumulation of PGs in the medium was demonstrated from 18 s to 5 h, with large increments during the first 30 min. Basal accumulation of PGs in the incubation medium was highest for 6-keto-PGF1 alpha (the stable metabolite of prostacyclin) greater than PGE2 greater than PGF2 alpha greater than thromboxane B2 (TXB2) and basal accumulation of PGF2 alpha and PGE2 measured in the medium was maximal on Day 10-11 of pseudopregnancy, concomitantly with a decline in secretion of progesterone. Addition of arachidonic acid (AA) dose-dependently increased synthesis of PGs, with absolute amounts of PGE2 greater than 6-keto-PGF1 alpha greater than PGF2 alpha greater than TXB2 and addition of 14 microM indomethacin markedly inhibited accumulation of all PGs measured. Luteinizing hormone (LH, 10 micrograms/ml) stimulated progesterone secretion on all days during pseudopregnancy, but not on the post-luteolytic Day 19. LH increased PGF2 alpha, PGE2 and 6-keto-PGF1 alpha secretion on Day 13 of pseudopregnancy by 76%, 91% and 28%, respectively, but not on the other days tested. Furthermore, stimulation of PG-synthesis by addition of AA abrogated the LH-induced progesterone accumulation markedly, but only on Day 13 of pseudopregnancy. Epinephrine (5 micrograms/ml) increased production of progesterone and also PGs, but only on Day 2 of pseudopregnancy, whereas oxytocin (100 mIU/ml) was found to be without effect on progesterone as well as PG secretion on all days tested. The results of the present study demonstrates the independent ability of the rat CL to synthesize PGG/PGH2-derived prostaglandins, including the putative luteolysin PGF2 alpha. Secondly, we demonstrate that LH and AA-induced increases in PGF2 alpha and PGE2 production during the luteolytic period, may be an autocrine or paracrine mechanism involved in luteolysis.     

Ovarian and uterine prostaglandin E2-9-ketoreductase activity in cyclic and pregnant ewes.

The regulation of luteal function in sheep appears to be dependent in part upon relative utero-ovarian concentrations of PGE2 and PGF2 alpha. Prostaglandin E2-9-ketoreductase converts PGE2 (a putative antiluteolysin) to PGF2 alpha. Enzymatic activity was measured in a cytosolic subcellular fraction of luteal and endometrial tissues collected on days 10, 13 and 16 of the estrous cycle or pregnancy. Respective days represented times before, during, and after the critical period for maternal recognition of pregnancy. Preparations of enzyme were incubated in the presence of tritiated PGE2. Radiolabeled PGF2 alpha (ie., product) was separated from PGE2 by gel filtration chromatography and quantified by liquid scintillation spectrometry. There were no significant differences due to time of tissue collection or pregnancy status in enzymatic activity of luteal tissues. Prostaglandin E2-9-ketoreductase activity isolated from endometria of open ewes was greater than their pregnant counterparts on days 13 and 16. Thus, the potential capacity of the ovine uterus to generate luteolytic PGF2 alpha from PGE2 substrate is elevated during an infertile estrous cycle.     

Prostaglandin F2 alpha, oxytocin and progesterone secretion by bovine luteal cells at several stages of luteal development: effects of oxytocin, luteinizing hormone, prostaglandin F2 alpha and estradiol-17 beta

Bovine luteal cells from Days 4, 8, 14 and 18 of the estrous cycle were incubated for 2 h (1 x 10(5) cells/ml) in serum-free media with one or a combination of treatments [control (no hormone), prostaglandin F2 alpha (PGF), oxytocin (OT), estradiol-17 beta (E) or luteinizing hormone (LH)]. Luteal cell conditioned media were then assayed by RIA for progesterone (P), PGF, and OT. Basal secretion of PGF on Days 4, 8, 14 and 18 was 173.8 +/- 66.2, 111.1 +/- 37.8, 57.7 +/- 15.4 and 124.3 +/- 29.9 pg/ml, respectively. Basal release of OT and P was greater on Day 4 (P less than 0.01) than on Day 8, 14 and 18 (OT: 17.5 +/- 2.6 versus 5.6 +/- 0.7, 6.0 +/- 1.4 and 3.1 +/- 0.4 pg/ml; P: 138.9 +/- 19.5 versus 23.2 +/- 7.5, 35.4 +/- 6.5 and 43.6 +/- 8.1 ng/ml, respectively). Oxytocin increased (P less than 0.01) PGF release by luteal cells compared with control cultures irrespective of day of estrous cycle. Estradiol-17 beta stimulated (P less than 0.05) PGF secretion on Days 8, 14 and 18, and LH increased (P less than 0.01) PGF production only on Day 14. Prostaglandin F2 alpha, E and LH had no effect on OT release by luteal cells from any day. Luteinizing hormone alone or in combination with PGF, OT or E increased (P less than 0.01) P secretion by cells from Days 8, 14 and 18. However on Day 8, a combination of PGF + OT and PGF + E decreased (P less than 0.05) LH-stimulated P secretion. These data demonstrate that OT stimulates PGF secretion by bovine luteal cells in vitro. In addition, LH and E also stimulate PGF release but effects may vary with stage of estrous cycle.     

Anti-apoptotic roles of prostaglandin E2 and F2alpha in bovine luteal steroidogenic cells

Production of prostaglandins (PGs) and expression of their receptors have been demonstrated in bovine corpus luteum (CL). The aim of the present study was to determine whether PGE2 and PGF2alpha have roles in bovine luteal steroidogenic cell (LSC) apoptosis. Cultured bovine LSCs obtained at the midluteal stage (Days 8-12 of the cycle) were treated for 24 h with PGE2 (0.001-1 microM) and PGF2alpha (0.001-1 microM). Prostaglandin E2 (1 microM) and PGF2alpha (1 microM) significantly stimulated progesterone (P4) production and reduced the levels of cell death in the cells cultured with or without tumor necrosis factor alpha (TNF)/interferon gamma (IFNG), in the presence and absence of FAS ligand (P < 0.05). Furthermore, DNA fragmentation induced by TNF/IFNG was observed to be suppressed by PGE2 and PGF2alpha. Prostaglandin E2 and PGF2alpha also attenuated mRNA expression of caspase 3 and caspase 8, as well as caspase 3 activity (P < 0.05) in TNF/IFNG-treated cells. FAS mRNA and protein expression were decreased only by PGF2alpha (P < 0.05). A specific P4 receptor antagonist (onapristone) attenuated the apoptosis-inhibitory effects of PGE2 and PGF2alpha in the absence of TNF/IFNG (P < 0.05). A PG synthesis inhibitor (indomethacin) reduced cell viability in PGE2- and PGF2alpha-treated cells (P < 0.05). A specific inhibitor of cyclooxygenase (PTGS), PTGS2 (NS-398), also reduced cell viability, whereas an inhibitor of PTGS1 (FR122047) did not affect it. The overall results suggest that PGE2 and PGF2alpha locally play luteoprotective roles in bovine CL by suppressing apoptosis of LSCs.     

Concentrations of prostaglandins E2, F2 alpha and 6-keto-prostaglandin F1 alpha in the utero-ovarian venous plasma of nonpregnant and early pregnant ewes

The effect of pregnancy on concentrations of prostaglandins E2, F2 alpha and 6-keto-prostaglandin F1 alpha (PGE2, PGF2 alpha and 6-keto-PGF1 alpha) in utero-ovarian venous plasma was examined in ewes on Days 10 through 14 after estrus, an interval which includes the critical period for maternal recognition of pregnancy. The utero-ovarian vein ipsilateral to a corpus luteum was catheterized on Day 9 or 10 in 6 pregnant and 8 nonpregnant ewes. Five blood samples were collected at 30-min intervals for 2 h beginning at 0500 and 1700 h daily. Sampling began at 0500 h on the day after catheterization. The mean and variance within each 2-h collection period were calculated for each ewe. The natural logarithm of the variance in each collection period (ln variance) was used as an estimate of the fluctuations in secretory activity by the endometrial-conceptus complex. Patterns of the mean concentrations of PGE2 were different between pregnant and nonpregnant ewes (P less than 0.01); PGE2 being higher in the pregnant ewes beginning on Day 13. There was a trend for the patterns of ln variance in PGE2 to differ (P less than 0.1) with pregnancy status over the entire period; ln variance was greater in pregnant ewes beginning on Day 13. The patterns of the mean concentrations and ln variances for PGF2 alpha and 6-keto-PGF1 alpha did not differ between pregnant and nonpregnant ewes. There were significant increases in both of these prostaglandins over time, independent of pregnancy status (P less than 0.01). The association of higher concentrations of PGE2 in utero-ovarian venous plasma with early pregnancy is consistent with the hypothesis that PGE2, originating from the uterus and/or conceptus, is one factor involved in maintenance of the corpus luteum of pregnancy.     

Effect of decidual tissue on the uterine production of prostaglandins in pseudopregnant rats.

The concentration of prostaglandin F (PGF) in uterine vein plasma of non-traumatized pseudopregnant rats and pseudopregnant rats with deciduomata were not significantly different from each other at any of the times of pseudopregnancy studied (Days 7, 10 and 12). There was a significant increase in PGF levels on Day 10 in both groups of pseudopregnant animals (P less than 0-05) compared to the Day 4 values, and PGE values were significantly greater on Day 10 in the decidual tissue-bearing rats (P less than 0-01). A slight but not significant elevation in PGE concentration was observed on Days 7 and 12 in rats with deciduomata, but there was no significant difference in the control rats on Days 4, 7, 10 or 12. The results indicate that the prolongation of pseudopregnancy in rats with deciduomata is not due to a decreased production of uterine PGs and lend support to the recent suggestion of a luteotrophic effect of decidual tissue in the rat.     

Prostaglandin translocation from the lumen of the rabbit uterus in vitro in relation to day of pregnancy or pseudopregnancy

Transport of 3H-labeled prostaglandins (PGs) E2 and F2 alpha from the uterine lumen across the uterine wall has been studied in rabbit uteri in vitro in incubations lasting up to 180 min, in relation to sexual state of the rabbit, incubation temperature, intraluminal PG concentration, addition of metabolic inhibitors and time of incubation. PG accumulation by the tissue increased rapidly up to 30 min and then remained relatively constant. By 30 min, radioactivity was found in the external incubation medium, and this increased linearly with time. The translocation of PGF2 alpha was significantly greater in pseudopregnant than in pregnant animals on Day 6, whereas that of PGE2 was significantly higher in pregnant than in pseudopregnant animals on Day 6.8. In pregnant animals, both PGF2 alpha and PGE2 were translocated to the exterior more rapidly on Day 6.8 than on Days 5 or 6. Transport of PGs was reduced by low temperature, unaffected by metabolic inhibitors and only that of PGE2 increased with increased (5 microM) intraluminal concentrations. During incubation, the tissue remained viable as judged by T/M ratios (dpm tissue/dpm medium) for 204 thallium. Transport of [14C] sucrose was much slower than that of [14C] urea, which was greater than the fastest rates exhibited by the PGs. In general, amounts of radioactivity found in antimesometrial, mesometrial and lateral portions of the uterine wall, or in implantation and interimplantation areas did not differ, but more was found in the endometrium than the myometrium. PGF2 alpha was translocated unmetabolized to the external medium, while only two-thirds of the PGE2 was translocated unchanged, and one-third converted to PGF2 alpha. It is concluded that the rabbit uterus shows some selectivity in handling PGs in relation to stage of pregnancy.     

Effects of tumor necrosis factor-alpha on secretion of prostaglandins E2 and F2alpha in bovine endometrium throughout the estrous cycle

To determine the physiological significance of tumor necrosis factor-alpha (TNFalpha) in the regulation of endometrial prostaglandin (PG) release in cattle, we investigated the effects of TNFalpha on the secretion of PGE2 and PGF2alpha by bovine endometrium during the estrous cycle. Bovine uteri were classified into six stages (estrus: Day 0, early luteal 1: Days 2 to 3, early luteal 11: Days 5 to 6, mid-luteal: Days 8 to 12, late luteal: Days 15 to 17 and follicular: Days 19 to 21). After 1 h of pre-incubation, endometrial tissues (20 to 30 mg) were exposed to 0 or 0.6 nM TNFalpha for 4 h. The PGE2 concentrations in the medium were higher in the luteal stages than in the follicular stage and in estrus. In contrast, PGF2alpha concentrations were higher in the follicular stage and in estrus than in the luteal stages. The ratio of the basal concentrations of PGE2 and PGF2alpha (PGE2/PGF2alpha ratio) was higher in the luteal stages than in the follicular stage and in estrus. Although TNFalpha stimulated both PGE2 and PGF2alpha secretion during the entire period of the estrous cycle, the level of stimulation of TNFalpha on PGE2 output by the bovine endometrium does not show the same cyclical changes as that shown on PGF2alpha output. The stimulation of TNFalpha resulted in a decrease in the PGE2/PGF2alpha ratio only in the late luteal stage. Furthermore, TNFalpha stimulated PGE2 secretion in stromal, but not epithelial cells. The overall results suggest that TNFalpha is a potent regulator of endometrial PGE2 secretion as well as PGF2alpha secretion during the entire period of estrous cycle, and that TNFalpha plays different roles in the regulation of secretory function of bovine endometrium at different phases of the estrous cycle.     

Specific PGF-2 alpha binding by the corpus luteum of the pregnant and non-pregnant mare.

The binding of prostaglandin (PG) F-2 alpha to corpora lutea (CL) from pregnant and non-pregnant Pony mares was examined. Studies of the rates of association and dissociation indicated that [3H]PGF was bound specifically and reversibly to a luteal cell membrane preparation (MP) that was isolated by high speed (100,000 g) ultracentrifugation. Various PGs and PG metabolites displaced [3H]PGF from the receptors in the following decreasing order: PGF-2 alpha greater than 13, 14-dihydro-PGF-2 alpha = 13,14-dihydro-15-keto PGF-2 alpha greater than PGD-2 greater than PGF-1 alpha = PGE-2 greater than PGE-2 beta greater than PGE-1. These data implicate the 9 alpha-OH and 5,6 cis double bond as major contributors to PGF receptor recognition. The membrane preparation appeared to contain at least two receptor populations, a high affinity, low capacity and a low affinity, high capacity receptor. The binding of PGF (pg/mg MP protein +/- s.e.m. (n)) to CL of the non-pregnant mare increased from 4.09 +/- 11.6 (4), on Day 4 after ovulation, to reach maximal levels by Day 12, 15.01 +/- 2.5 (4), and declined thereafter. In pregnancy the binding of PGF continued to increase until Day 18, reaching 27.47 +/- 1.7 (3), before it declined on Day 20. The reduction in binding by Day 16 in the non-pregnant mare may reflect the process of luteolysis, while high PGF binding capacity of CL between Days 16 and 18 of pregnancy indicated that luteal maintenance during pregnancy is not associated with a reduction of PGF binding capabilities.     

Progesterone levels and litter performance of sows following postpartum administration of prostaglandin F(2alpha)

A total of 101 sows was used to examine postpartum progesterone levels and litter performance following administration of 15 mg prostaglandins F(2alpha) (PGF(2alpha) n = 48) given within 12 h after farrowing. Daily blood samples and rectal temperatures were taken from all sows during the first 3 d post partum. Plasma progesterone (P(4)) concentrations were determined by radioimmunoassay (RIA). Regardless of treatment, plasma P(4) levels for all sows decreased in a similar fashion over the 3 d sampled. Mean (+/- SEM) P(4) on Day 2 (0.55 +/- 0.06 ng/ml) and Day 3 (0.38 +/- 0.04 ng/ml) were lower (P<0.01) than on Day 1 (0.98 +/- 0.08 ng/ml). Rectal temperature did not differ between PGF(2alpha) treated and nontreated sows nor was it different over the days measured. Litter characteristics, including survival rates on Day 7 and at weaning, and body weight on Days 3 and 35, were not affected by treatment. It was concluded that PGF(2alpha) administration to sows within 12 h post farrowing had no affect on the rate of luteal regression, as determined by P(4) concentration, nor on subsequent litter performance.     

Prostacyclin, prostaglandin F2 alpha and progesterone production by bovine luteal cells during the estrous cycle

Corpora lutea (CL) were collected from Holstein heifers on Days 5, 10, 15 and 18 (5/day) of the estrous cycle. Dispersed luteal cell preparations were made and 10(6) viable luteal cells were incubated with bovine luteinizing hormone (LH) and different amounts of arachidonic acid in the presence and absence of the prostaglandin (PG) synthetase inhibitor indomethacin. The concentrations of progesterone, PGF2 alpha and 6-keto-PGF1 alpha, the stable inactive metabolite of prostacyclin (PGI2), were measured. Day 5 CL had the greatest initial content of 6-keto-PGF1 alpha (1.01 +/- 0.16 ng/10(6) cells), and synthesized more 6-keto-PGF1 alpha (2.55 +/- 0.43) than CL collected on Days 10 (0.57 +/- 0.11), 15 (0.08 +/- 0.05) and 18 (0.19 +/- 0.03) during a 2-h incubation period. Arachidonic acid stimulated the production of 6-keto-PGF1 alpha by Days 10, 15 and 18 luteal tissue. PGF2 alpha was produced at a greater rate on Day 5 (0.69 +/- 0.17 ng/10(6) cells) than on Days 10 (0.06 +/- 0.01), 15 (0.04 +/- 0.02) and 18 (0.08 +/- 0.01). Arachidonic acid stimulated and indomethacin inhibited the production of PGF2 alpha, in most cases. The initial content of 6-keto-PGF1 alpha was higher than that of PGF2 alpha on all days of the cycle and more 6-keto-PGF1 alpha was synthesized in response to arachidonic acid addition. The ratio of 6-keto-PGF1 alpha content to PGF2 alpha content was 4.39, 2.30, 1.25 and 1.13 on Days 5, 10, 15 and 18, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intraluteal infusions of prostaglandins of the E, D, I, and A series prevent PGF2 alpha-induced, but not spontaneous, luteal regression in rhesus monkeys

A luteotropic role for prostaglandins (PGs) during the luteal phase of the menstrual cycle of rhesus monkeys was suggested by the observation that intraluteal infusion of a PG synthesis inhibitor caused premature luteolysis. This study was designed to identify PGs that promote luteal function in primates. First, the effects of various PGs on progesterone (P) production by macaque luteal cells were examined in vitro. Collagenase-dispersed luteal cells from midluteal phase of the menstrual cycle (Day 6-7 after the estimated surge of LH, n = 3) were incubated with 0-5,000 ng/ml PGE2, PGD, 6 beta PGI1 (a stable analogue of PGI2), PGA2, or PGF2 alpha alone or with hCG (100 ng/ml). PGE2, PGD2, and 6 beta PGI1 alone stimulated (p less than 0.05) P production to a similar extent (2- to 3-fold over basal) as hCG alone, whereas PGA2 and PGF2 alpha alone had no effect on P production. Stimulation (p less than 0.05) of P synthesis by PGE2, PGD2, and 6 beta PGI1 in combination with hCG was similar to that of hCG alone. Whereas PGA2 inhibited gonadotropin-induced P production (p less than 0.05), that in the presence of PGF2 alpha plus hCG tended (p = 0.05) to remain elevated. Second, the effects of various PGs on P production during chronic infusion into the CL were studied in vivo. Saline with or without 0.1% BSA (n = 12), PGE2 (300 ng/h; n = 4), PGD2 (300 ng/h; n = 4), 6 beta PGI1 (500 ng/h; n = 3), PGA2 (300 ng/h; n = 4), or PGF2 alpha (10 ng/h; n = 8) was infused via osmotic minipump beginning at midluteal phase (Days 5-8 after the estimated LH surge) until menses. In addition, the same dose of PGE, PGD, PGI, or PGA was infused in combination with PGF2 alpha (n = 3-4/group) for 7 days. P levels over 5 days preceding treatment were not different among groups. In 5 of 8 monkeys receiving PGF2 alpha alone, P declined to less than 0.5 ng/ml within 72 h after initiation of infusion and was lower (p less than 0.05) than controls. The length of the luteal phase in PGF2 alpha-infused monkeys was shortened (12.3 +/- 0.9 days; mean +/- SEM, n = 8; p less than 0.05) compared to controls (15.8 +/- 0.5). Intraluteal infusion of PGE, PGD, PGI, or PGA alone did not affect patterns of circulating P or luteal phase length.(ABSTRACT TRUNCATED AT 400 WORDS)     

Prostaglandin release from the guinea-pig uterus superfused in vitro. Effect of stage of estrous cycle, progesterone, estradiol, oxytocin and A23187

Prostaglandin (PG) E2 was the major PG released from the superfused guinea-pig uterus on Day 7, followed by in descending order 6-oxo-PGF1 alpha, thromboxane (TX) B2 and PGF2 alpha. However, the outputs of all four substances were low and were very similar. By Day 15, PGF2 alpha output from the superfused uterus had increased 21.9-fold, whereas the outputs of PGE2, 6-oxo-PGF1 alpha and TXB2 had increased only 1.8-, 2.9- and 1.2-fold, respectively. A mechanism is apparently "switched on" between Days 7 and 15 which causes a fairly specific increase in the release of PGF2 alpha from the uterus. Progesterone and/or estradiol had no effect on PG or TX release when superfused over the uterus on Day 7, nor did they have any effect on PG and TX release from the Day 15 uterus when administered separately. When administered together, however, they significantly inhibited PGF2 alpha, PGE2 and 6-oxo-PGF1 alpha, but not TXB2, release from the Day 15 uterus. Oxytocin had no effect on PG release from the Day 7 or Day 15 uterus, while A23187 stimulated PGF2 alpha, 6-oxo-PGF1 alpha and, to a lesser extent, PGE2 release from the uterus on both Days 7 and 15. Oxytocin is apparently not important for stimulating PGF2 alpha release from the guinea-pig uterus in relation to luteolysis, whereas increasing intracellular free Ca++ levels may be part of the mechanism for "switching on" uterine PG synthesis. Furthermore, changes in intracellular free Ca++ levels in the endometrium may be responsible for the pulsatile nature of PGF2 alpha release from the uterus.     

Studies on prostaglandin metabolism in corpora lutea of rabbits during pregnancy and pseudopregnancy

Corpora lutea and ovarian stromal tissue were analysed for prostaglandin (PG) concentrations and activities of enzymes involved in PG metabolism at 8, 10, 12, 13 and 15 days after induction of ovulation. In CL of pseudopregnant rabbits, the PGE-2-9-ketoreductase (PGE-2-9-KR) was highly active on Days 10, 12 and 15 when compared with Day 8 (P less than 0.01; P less than 0.001; P less than 0.05). In pregnant animals PGE-2-9-KR activity was only increased on Day 12 (P less than 0.05) but declined to basal levels on Days 13 and 15. Comparing PGE-2-9-KR activity of pseudopregnant and pregnant animals, a significant elevation was found on Day 15 of pseudopregnancy (P less than 0.025). Activities of PG-15-hydroxydehydrogenase did not exhibit any significant changes with time in pseudopregnant or pregnant rabbits. PGE-2 concentrations were increased on Days 12, 13 and 15 (P less than 0.025) when compared with Day 8. Changes in PGF-2 alpha concentrations paralleled those of PGE-2-9-KR. The concentrations of PG metabolites 13,14-dihydro-15-keto-PGE-2 and -PGF-2 alpha were lower than those of the primary PGs and did not show stage-specific changes in pseudopregnant and pregnant animals. These results demonstrate that the rabbit CL possesses enzymes to convert PGE-2 to PGF-2 alpha and to metabolize both PGs. PGE-2-9-KR may be involved in regulating the PGF-2 alpha/PGE-2 ratio and possibly in controlling the life-span of the corpus luteum.     

Modification of prostaglandin F-2 alpha synthesis and release in the ewe during the initial establishment of pregnancy

Pregnant (N = 10) and non-pregnant (N = 10) ewes were bled every 2 h from Days 12 to 17 after oestrus (oestrus = Day 0). Plasma concentrations of progesterone, 15-keto-13,14-dihydro-PGF-2 alpha and 11-ketotetranor-PGF metabolites were determined in all samples. The number of PGF-2 alpha pulses in non-pregnant ewes was 8.2 +/- 0.4 (mean +/- s.e.m.) with an interpulse interval of 10.7 +/- 0.7 h. Two or 3 pulses of low frequency (interpulse interval = 13.4 +/- 1.6 h) occurred in most non-pregnant ewes before the onset of luteolysis; the interpulse interval then decreased to 7.9 +/- 0.4 h for the 6.0 +/- 0.3 pulses temporally associated with luteolysis. In contrast, the number of PGF-2 alpha pulses in pregnant ewes was lower (2.5 +/- 0.7, 0-8) and the interpulse intervals longer (18.9 +/- 6.1 h). Most pulses occurred on Days 14 and 15 in the pregnant and non-pregnant ewes. The mean concentrations of both PGF-2 alpha metabolites in non-pregnant ewes were highest on Day 15 while basal levels of both metabolites remained constant at all times. In pregnant ewes, the mean concentrations of both metabolites were highest on Day 14; basal concentrations of both metabolites were also highest on Day 14. The mean concentrations of 15-keto-13,14-dihydro-PGF-2 alpha were higher in pregnant than in non-pregnant ewes on Days 13 and 14 (P less than 0.05) and higher in non-pregnant than pregnant ewes on Day 15 (P less than 0.05). The basal concentrations of the 15-keto metabolite were higher in pregnant than non-pregnant ewes at Days 13, 14, 15, 16 and 17 (P less than 0.05). Both the mean and the basal concentrations of 11-ketotetranor-PGF metabolites were higher in pregnant than in non-pregnant ewes on Day 14 (P less than 0.05). It is concluded that uterine production of PGF-2 alpha peaks at Days 14-15 after oestrus in pregnant and non-pregnant ewes. Patterns of release differ, however, in that non-pregnant ewes have a pulsatile PGF-2 alpha pattern superimposed on a constant baseline, while pregnant ewes have an increasing basal secretory pattern which is more nearly continuous, i.e. not pulsatile in form. Modification of pulsatile PGF-2 alpha synthesis and release is therefore a key aspect of prolongation of luteal function at the beginning of pregnancy in the ewe.