Midtrimester pregnancy interruption and the placental progesterone levels

Placental progesterone contents were studied in 10 patients therapeutically aborted at midtrimester by intraamniotic infusions of hypertonic saline, and from 14 patients (12–20 weeks) aborted by intraamniotic instillation of prostaglandin F_2∝. The mean S.E. of the progesterone was 1.99± 0.07 ug/g. placental tissue in the first group, while with prostaglandin abortion the placental progesterone was 1.45± 0.09 ug/g. tissue, which is significantly lower than the results in the first group (P=0.001). The possible mechanism of action of prostaglandin as an effective abortifacient is discussed.     

Effect of blastocysts on rat ovarian steroidogenesis in early pregnancy.

The biosynthesis of ovarian progesterone and 20alpha-hydroxypregn-4-en-3-one (20alpha-OHP) was studied in rats with pituitaries autotransplanted beneath the kidney capsule (APTr rats) 1 1/2 days after ovulation. Some animals underwent tubal ligation 1-2 weeks prior to mating. Incubated ovarian tissue slices showed an accumulation of progesterone of 64 plus or minus 11 mcg/g tissue, and a progesterone/20alpha-OHP ratio of .32 plus or minus .16. Ovarian tissue from APTr rats with viable blastocysts synthesized considerably more progesterone than tissue from tubal ligated APTr rats. The increased concentrations of progesterone were associated with decreased concentrations of 20alpha-OHP. The accumulation of progesterone in tissue from unmated APTr rats, APTr rats cervically stimulated at proestrus, and similar cervically stimulated rats with traumatized uteri was 42 plus or minus 5, 16 plus or minus 4 and 18 plus or minus 9 net mcg/g tissue, respectively. The progesterone accumulation in tissue from cervically stimulated rats was thus similar to that in tissue from tubal ligated animals. This inhibition by cervical stimulation was overcome by stimuli from the blastocysts. The results suggest that the blastocyst secretes a substance that is more active in promoting progesterone formation than pituitary prolactin.     

Reassessment of systemic administration of prostaglandins for induction of midtrimester abortion

This investigation was conducted to evaluate the abortifacient efficacy of vaginal and intramuscular administration of different dose schedules of the 15-methyl analogues of prostaglandin F2 alpha. Both 15-methyl PGF2 alpha and 15-methyl PGF methyl ester can be absorbed from the vagina in sufficient amounts to induce abortion. The potency of the methyl ester was approximately twice that of the free acid. The most successful treatment schedule consisted of an initial dose of 0.5 mg of the methyl ester followed by 1.0 or 2.0 mg every third hour. On this treatment all patients aborted within 24 hours. Initially 200 ug of 15-methyl-PGF2 alpha was given. The dose was increased to 400 ug or occassionally to 500 ug depending on the effect and tolerance of the patient and repeated every third hour. The treatment schedule resulted in a 100% abortion rate and the mean induction-abortion interval was 16.1 hours. Both routes were associated with a higher frequency of side effects than that reported for intraamniotic administration of 15-methyl-PGF2 alpha. It seems justified to conclude that the intraamniotic route is preferable after the 14th week when the uterine cavity is easy to puncture, but that vaginal or intramuscular injections of the compounds could be an alternative in late first trimester and early second trimester cases.     

Single intraamniotic injections of prostaglandin F-2-alpha as an abortifacient agent: size of effective dose and effect of parity

This report discusses the authors' experience with intraamniotic administration of single doses of the prostaglandin PGF2alpha as an abortifacient agent. 98 healthy women between the 12th and 26th week of pregnancy admitted to the Clinical Research Unit of the North Carolina Memorial Hospital were given a single intraamniotic dose of PGF2a administered through an indwelling polyethelene catheter inserted either transabdominally or transvaginally. The drug was given as Tham salt with the first 5 mg of any dose being given at the rate of 1 mg/minute for 5 minutes, followed by more rapid administration of the balance of the dose. Abortion which did not occur within 48 hours was considered a failure. Each patient received 1 of the following dosages: 25, 40, 50, and 75. 9 (64%) of 14 patients given 25 mg PGF2a aborted within the 48-hour period. The percentages of abortion in the doses 40, 50, and 75 mg were 88.9% (9 patients), 96.7% (60 patients) and 93.3% (15 patients) respectively. As these figures were almost similar, the 84 patients were combined as a single group (84 patients) relative to the injection-abortion time, effect of parity, and stage of gestation at which the abortion was carried out. Half of the patients in this combined group aborted in approximately 21 hours; more than 90% at the end of 32 hours; and 95% at the end of the 48 hours post-injection. For comparison, the cumulative abortion curve of 552 patients who had intraamniotic saline for abortion showed that 50% of the women aborted within 31 hours, 84% within 48 hours, and 97% within 72 hours. Prostaglandin induced abortions thus are shown to reach the 50% level 10 hours before the saline patients, and the 90% level about 21 hours before the saline patients. Significant side effects (presented elsewhere) were observed in all groups, with the incidence increasing at higher dosages. Mean induction-abortion time for nulliparas at all dosages was 17.4 hours; for multiparas, 20.4 hours. There was no clear relationship between gestational age and parity. The study shows that the effective dose for inducing abortion with PGF2a lies within the 40 to 50 mg dose range.     

Studies on experimental growth retardation in sheep. The effect of removal of a endometrial caruncles on fetal size and metabolism.

Experimental intrauterine growth retardation was studied in sheep. Endometrial caruncles (anlagen of maternal cotyledon) were removed before pregnancy and at a second operation, catheters were implanted into the ewe and fetus at 105-135 days of pregnancy. Three groups of fetuses were defined: low birthweight-for-dates (small-caruncle), normal birthweight-for-dates (normal-sized-caruncle) from ewes which had endometrial caruncles removed and the controls. The mean placental weights in these groups were 139 plus or minus 5 g, 283 plus or minus 46 g, 334 plus or minus 22 g respectively. The brains, kidneys and adrenals of the small-caruncle-fetuses were significantly greater in proportion to body weight than in the controls and the appearance of ossification centres was delayed. Arterial oxygen tension was lower and packed cell volume higher in the small-caruncle-fetuses (PaO2 15 plus or minus 0.6 mmHg; packed cell volume 37.3 plus or minus 1.6%) and normal sized caruncles (PaO2 20.7 plus or minus 1.2 mmHg; packed cell volume 35.2 plus or minus 0.7%) than in the controls (PaO2 23.2 plus or minus 0.7 mmHg; packed cell volume 29.8 plus or minus 0.7%). Plasma concentrations of glucose (0.65 plus or minus 0.12 micromol/ml), lactate (0.9 plus or minus 0.1 micromol/ml) and pyruvate (0.08 plus or minus 0.025 micromol/ml) were lower in small-caruncle fetuses than in the control fetuses (glucose 1.05 plus or minus 0.06 micromol/ml, lactate 1.83 plus or minus 0.7 micromol/ml, pyruvate 0.21 plus or minus 0.06 micromol/ml). The corresponding values for the normal-sized-caruncle fetuses were glucose 0.71 plus or minus 0.12, lactate 1.18 plus or minus 0.7 and pyruvate 0.12 plus or minus 0.03 micromol/ml. The plasma concentration of alanine in the small-caruncle-fetuses (0.25 plus or minus 0.09 micromol/ml) was higher than in the normal-sized-caruncle (0.073 plus or minus 0.009 micromol/ml) or control fetuses (0.12 plus or minus 0.013 micromol/ml). The results indicate that fetal growth retardation due to restriction of placental growth after removal of endometrial caruncles is associated with chronic hypoxaemia, polycythaemia and hypoglycaemia. The restriction of nutrient supply probably accounts for the altered pattern of fetal growth but the relative importance of the changes observed remains uncertain.     

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.     

Single extra-amniotic injection of prostaglandin E2 in viscous gel to induce mid-trimester abortion.

In a preliminary study a single extra-amniotic injection of 1.5 mg of prostaglandin E-2 incorporated into an aqueous viscous gel was given to 24 patients aborted within 24 hours, and the mean induction-abortion interval (plus or minus S.E. of mean) was 13.5 plus or minus 1.5 hours. Vomiting occurred in seven patients, and transient severe uterine cramps, pallor, nausea, and shivering occurred in one patient immediately after injection. Complete abortion occurred in 20patients. A delay in the time taken to abort seemed to be associated with an immediate and rapid rise in uterine tone after the injection which required prompt analgesia; this probably reflected rapid decidual absorption and dissolution of the prostaglandins away from their site of action. The degree of distention of the catheter-retaining balloon did not influence abortion times.     

Levels of prostaglandin F (PGF) in bovine endometrium uterine venous, ovarian arterial and jugular plasma during the estrous cycle (38789).

Prostaglandins F (PGF) were measured in uterine vein, ovarian artery, and jugular vein plasma and in the endometrial tissues at various times during the bovine estrous cycle, and were compared to peripheral plasma progesterone levels. Four groups of heifers at days 1-5, 10-14, 15-17 and 20-0 of the estrous cycle were studied. Low levels of PGF (48 plus or minus 12 ng/g dry tissue were measured in the endometrium on days 1-14 of the cycle. Higher values (131 plus or minus 9.0) were found at days 15 until the day of estrus (p less than 0.001). Similarly, very low levels of PGF were observed in the uterine vein plasma at days 1-14 (0.162) plus or minus 0.044) ng/mlM plus or minus S.E.), whereas on days 15 until the day of estrus the levels ranged from 1.5 to 3.0 ng/ml. The increases in uterine vein PGF on day 15 occurred even while peripheral plasma progesterone levels were still high. However, PGF was not elevated in either the ovarian artery or the jugular vein at any time during the cycle, even when uterine vein levels were greatly elevated. No differences in PGF content were detected in endometrial tissue from uterine horns adjacent or opposite to the functional corpus luteum.     

On the mechanism of midtrimester abortions induced by prostaglandin "impact"

Using Csapo's technique, a single dose of 24.3 +or- 1.1 mg prostaglandin F2alpha (PGF2alpha) had been delivered intraamniotically to 20 sedated pregnant patients (15.9 +or- 0.6 weeks pregnant) in order to provoke a PG impact (PGI), a consequent progesterone (P) withdrawal, and a conversion of the pharmacologically refractory normal pregnant uterus into a reactive organ. The side effects were occasional and acceptable and no further PGF2alpha treatment was needed except in 4 cases (5-10 mg). Only after the Oxytocin test showed that the uterus is becoming reactive, was 50 mU/minute oxytocin infused intravenously to facilitate the evolution of IUP to 93 +or- 3 mmHg and thus promote clinical progress. All the 20 patients aborted both the fetus and the placenta in 16.5 +or- 2.1 hours, but 8 women retained small placental residues to be removed by curettage. The Csapo score was a high 92 +or- 2. As early as 3 hours after PGI, the plasma P levels already decreased significantly. They continued to decline throughout the IAT and reached a 72% withdrawal when the fetus was aborted. 15 patients whose P withdrawal was rapid, aborted before the mean IAT, while those 5 women whose P withdrawal was slow aborted after this time. Thus, the rate of P withdrawal was direct while parity and gestational age indirectly related to the IAT. Studies are in progress to elucidate further the abortifacient action of PGF2alpha and through this knowledge promote predictable therapy.     

Midtrimester abortions induced by intraamniotic prostaglandin F2α treatment

A group of 10 patients, 16.2±0.5 weeks pregnant, received intraamniotically 10mg followed at 3 hours intervals by 5mg PG F2α. The total dose of 31.5±3.2mg PG F2α successfully induced abortion in 15.1±1.8 hours. Seven patients aborted completely and 3 incompletely. The rapid rise in RP was followed by a gradual increase in IUP and a continuing decrease in estradiol-17β and progesterone after a delay of about 6 hours. The systemic side effects were minimal and the vital signs and laboratory tests revealed no significant changes. The case reports of 4 additional patients are presented, and the mechanism of the abortifacient action of PG F2α is discussed. When further improved, intraamniotic PG F2α therapy may favorably compete with methods currently used for midtrimester legal abortions.     

Glucocorticoids do not share with progesterone the potent inhibitory action on prostaglandin synthesis in human proliferative phase endometrium

The action of progesterone and glucocortoids on human proliferative phase endometrium has been investigated using isolated fragments of endometrium cultured for 2 to 3 days. The action of progesterone (200–500 nM) in this system is to reduce prostaglandin F (PGF) production by 93 to 96%. This inhibition is considerably greater than the inhibitions observed using collagenase dispersed stromal or glandular cells. The addition of arachidonic acid (5ug/ml) increased the production of the control wells but did not overcome the inhibitory effect of progesterone. When endometrial fragments were cultured for 48 hr in the presence of progesterone and subsequently homogenized and incubated, there was no difference in PG production between the progesterone treated tissue and the controls.In a separate series of experiments the effect of progesterone (500 nM) was compared with cortisol (500 nM) and the synthetic glucocorticoid dexamethasone (100 nM) this dose of progesterone gave a 96% reduction in PGF synthesis but neither cortisol nor dexamethasone inhibited PGF production.     

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.     

New approach to the study of hormone-protein interaction using the microcalorimetric method.

Binding enthalpies of various hormones to bovine serum albumin (BSA) and human serum albumin (HSA) in 50 mM phosphate buffer, pH 7.4, at 37 degrees C have been determined by direct microcalorimetry. The observed enthalpies of binding of progesterone, testosterone, dihydrotestosterone, corticosterone and estriol to BSA were found to be -13.24 plus or minus 0.11 -10.31 plus or minus 0.02, -2.37 plus or minus 0.46, -17.64 plus or minus 0.32 and -17.14 plus or minus 0.36 kcal/mol of hormone, respectively. under the same experimental conditions the enthalpies of binding of progesterone, testosterone, dihydrotestosterone, corticosterone and estriol to HSA were found to be -23.94 plus or minus 0.32, -18.88 plus or minus 0.49, -11.14 plus or minus 0.02, -9.88 plus or minus 0.14 and -20.85 plus or minus 0.39 kcal/mol of hormone, respectively.     

Effect of prostaglandin F2 alpha on the secretion of human prolactin

This study examines the role of PGF2a (prostaglandin F2alpha) in increasing the secretion rate of human prolactin. 11 women (mean gestational period, 18 weeks) seeking pregnancy termination were divided into 4 groups: 1) Group 1 consisted of 6 women who received 30 mg initially of PGF2a injected intramuscularly and an additional 15 mg after 24 hours if abortion had not occured; mean induction to termination period was 38 hours; 2) Group 2 comprised of 3 women who received PGF2a (500-1500 ug) via the transcervical route at 1 to 2 hourly interval; average number of injections was 20; mean induction to termination period, 24 hours; 3) Group 3 had 2 women receiving hypertonic saline by intraamniotic injection; mean induction to termination period was 51 hours; 4) Group 4 had 4 women who served as controls; mean observation period, 20 hours. Venous blood samples were heparinized in tubes at intervals of 2 to 3 hours. A homologous radioimmunoassay using highly purified human prolactin (for iodination and standards) plus rabbit antihuman prolactin measured serum prolactin. Spikes of serum prolactin up to 550 ng/ml were observed at irregular intervals in 5 women in Group 1; the spikes were less frequent and of smaller amplitude in Groups 3 and 4. The increase in serum prolactin was dramatic and more sustained in Group 2 patients and peaked towards the end of the prostaglandin infusion. Serum prolactin of Group 2 patients were significantly higher than those of Groups 3 and 4 (p0.01). 5 of 9 women whose pregnancies were terminated by PGF2a lactated. However, there was no significant difference between the mean serum prolactin levels in women who lactated (136 ng/ml) and those who did not (120 ng/ml). Although PGF2a is not a lactogenic hormone, this study shows that PGF2a stimulates the secretion of human prolactin during second trimester pregnancy. The fact that the transcervical route caused a significant increase in serum prolactin and the intraamniotic route did not is attributed to the increased systemic absorption of PGF2a following transcervical administration. No correlation was seen between the presence or absence of lactation and the serum prolactin level following pregnancy termination with PGF2a.     

Differential inhibition of human prostaglandin release in vitro by a GnRH antagonist

Previously, we have demonstrated that the production of prostaglandins by human placental tissue varied with gestational age. In addition, we have shown that placental prostaglandin release was affected by GnRH, and that its response was also dependent on the gestational age of the placenta. Thus, we have studied the effect of a GnRH antagonist ([N-Ac-Pro¹, D-p-Cl-Phe², D-Nal (2)^3,6-LHRH, Syntex Research, Palo Alto, CA) on basal prostaglandin release from placentas of 6 to 15 weeks' gestaton and found that this antagonist (1 μg/ml) effects an inhibition of the release of prostaglandin E, prostaglandin F, and 13, 14-dihydro-15-keto-prostaglandin from placentas of 13 and 15 weeks of gestation. This effect was not overridden by GnRH at 10 times the antagonist concentration in the 13-week placental cultures, but was totally reversed by GnRH (10 μg/ml) in the 15-week placental cultures. These data demonstrate that this GnRH antagonist can affect human placental prostaglandin production at 13 to 15 weeks of gestation and indicate that endogenous placental GnRH-like activity may exert a control over placental prostaglandin release at this gestational stage.     

Transplacental carbohydrate and sugar alcohol concentrations and their uptakes in ovine pregnancy

The concentrations of glucose, fructose, sorbitol, glycerol, and myo-inositol in sheep blood and tissues have been reported previously (1--5). However, the other polyols that are at low concentrations have not been investigated in pregnant sheep due to technical difficulties. By using HPLC and gas chromatography-mass spectrometry, seven polyols (myo-inositol, glycerol, erythritol, arabitol, sorbitol, ribitol, and mannitol) and three hexoses (mannose, glucose, and fructose) were identified and quantified in four blood vessels supplying and draining the placenta (maternal artery, uterine vein, fetal artery, and umbilical vein). Uterine and umbilical blood flows were measured, and uptakes of all the polyols and hexoses in both maternal and fetal circulations were calculated. There was a significant net placental release of sorbitol to both maternal and fetal circulations. Fructose was also taken up significantly by the uterine circulation. Maternal plasma mannose concentrations were higher than fetal concentrations, and there was a net umbilical uptake of mannose, characteristics that are similar to those of glucose. Myo-inositol and erythritol had relatively high concentrations in fetal plasma (697.8 plus minus 53 microM and 463.8 plus minus 27 microM, respectively). The ratios of fetal/maternal plasma arterial concentrations were very high for most polyols. The concentrations of myo-inositol, glycerol, and sorbitol were also high in sheep placental tissue (2489 plus minus 125 microM/kg wet tissue, 2119 plus minus 193 microM/kg wet tissue, and 3910 plus minus 369 microM/kg wet tissue), an indication that these polyols could be made within the placenta.     

Midtrimester abortion induced by single intra-amniotic instillation of two dose schedules of 15(S)-15-methyl-prostaglandin F2alpha.

Midtrimester abortion was successfully induced in a series of 20 patient by intraamniotic instillation of 15(S)-15-methyl-prostaglandin F2alpha with a mean abortion time of 17.78 hours. The patients in this study was divided into two groups, Groups 1 received an initial dose of 2.5 mg 15-ME-PGF2alpha and aborted in a mean time of 16.26 hours. The patients in Group II received 3.0 mg 15-ME-PGF2alpha and aborted in a mean time of 18.94 hours. There was no significant difference in the abortion time, occurrence of side effects or the initiation of uterine activity between Group I and Group II. Parous patients aborted somewhat faster than nulliparous patients but this difference was not significant. In this study 80% of the patients aborted in 24 hours or less, and the intra-amniotic instillation of 15-ME-PGF2alpha was an effective abortifacient technique from the 15th to the 23rd week of gestation. The uterine response to intra-amniotic instillation of 15-ME-PGF2alpha was characterized by the gradual appearance of low amplitude, high frequency contractions accompanied by a rise in baseline intrauterine tonus. Uterine activity developed gradually and peaked at 1:50 hours after intraamniotic instillation of 15-ME-PGF2alpha. In this small series 15-ME-PGF2alpha administered via intra-amniotic instillation did not appear to have a distinct advantage over the naturally occuring PGF2alpha administered by the same method for the induction of midtrimester abortion; a large series in indicated to define the advantage of either technique.     

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.     

Role of progesterone and estrogen in development of uterine tone in mares

In two experiments (30 mares/experiment), the uterus was recorded as having flaccid tone characteristic of estrus or seasonal anestrus (tone score 1), intermediate tone characteristic of diestrus (tone score 2), or increased or maximal tone characteristic of early pregnancy (tone score 3 or 4). In Experiment I (five mares/group), uterine tone in seasonally anovulatory mares was not altered significantly from the flaccid state by daily administration of 100 mg progesterone plus 1 mg estradiol 17beta or 1 mg estradiol 17beta alone. Uterine tone in seasonally anovulatory mares receiving 100 mg progesterone alone increased to intermediate level (score 2; P<0.05) and remained there throughout the treatment period. Tone scores in the group receiving a 14-d progesterone priming period followed by progesterone plus estradiol were higher (P<0.02) on Days 16 to 28 than scores in the group receiving progesterone alone throughout the treatment period. In Experiment II, (five mares/group), steroid treatments were begun on Day 10 postovulation. The combination of 1 mg exogenous estradiol plus progesterone produced greater uterine tone than exogenous progesterone alone. There were no significant differences between the pregnant control group and the group receiving progesterone plus 1 mg estradiol. There were no significant differences between the group receiving progesterone alone and the group receiving progesterone plus 5 mg estradiol. Results supported the hypothesis that the maximum uterine tone of early pregnancy is caused by progesterone priming followed by exposure to low levels of estradiol plus continued exposure to progesterone.     

Termination of early gestation with vaginal prostaglandin F2α tablets

The abortifacient activity of prostaglandin F_2α was investigated by placing one or two 50 mg tablets of prostaglandin F_2α in THAM salt into the vagina of nine women less than 4 weeks pregnant at intervals of 2 to 4 hours for a 24 hour period. Serum levels of HCG, estradiol (E₂), progesterone and 17α-hydroxyprogesterone were measured by radioimmunoassay prior to starting therapy and at frequent intervals thereafter for 48 hours. All but two patients had significant side-effects, mainly diarrhea and vomiting, indicating that systemic absorption took place. Although bleeding was induced in 8 of 9 women, only 3 had complete abortions. A D&C was performed on all patients 48 hours after starting therapy. A significant fall in HCG levels was noted only in the patients who aborted. Only 3 of the 9 women had significant changes in steroid levels. A fall in progesterone and 17α-hydroxyprogesterone occurred in the 3 women who aborted and took place following the fall in HCG. Estradiol levels remained in the same range in all subjects. These findings indicate that prostaglandin F_2α when administered in this vehicle and this dosage is relatively ineffective as an abortifacient. When effective, its action would appear to be due to contractions of uterine muscle and not secondarily to luteolysis.