Premature Luteal Regression Research Articles

Endocrinology in luteal phase and implantation

The normality of the luteal phase after superovulation depends on the method and adequacy of the stimulation regimen. In comparison with natural cycles, the luteinisation of multiple follicles produces higher concentrations of steroids in blood, and soon after ovulation a correct ratio of serum oestradiol (E2) to progesterone is critical to establish viable pregnancies. Out of phase and asynchronous endometria can arise after stimulation with clomiphene (CC) alone or in association with human menopausal gonadotrophin (HMG), and pregnancies mostly arose in patients with advanced endometrial characteristics and elevated post-ovulatory levels of serum progesterone after HMG stimulation. Increasing plasma progesterone concentrations in the early luteal phase with natural progesterone can thus be considered as a rational approach to improve rates of implantation. Premature luteal regression is frequently observed after HMG stimulation whether or not in association with gonadotrophin releasing-hormone agonists (GnRHa). Support to the theca lutein cells is mandatory before sufficient human chorionic gonadotrophin (HCG) is produced by the embryo. Deficient luteal phases can be treated with hormonal support, but the efficacy of routine luteal supplementation after ovarian hyperstimulation has still to be proven in larger controlled trials.

Effects of testosterone and 5α-dihydrotestosterone on luteal lifespan in dairy heifers

Endogenous concentrations of testosterone increase approximately 7 d prior to estrus in cattle and goats. Inhibition of testosterone synthesis results in a delay of luteal regression in both species. The purpose of this experiment was to determine if treatment with testosterone or 5α-dihydrotestosterone (DHT), 2 to 6 d prior to the endogenous rise in testosterone, would result in premature luteal regression. Sixteen heifers were randomly assigned to one of three treatment groups: 1) Control (n = 6); 2) testosterone (100 μg, n = 5); or 3) DHT (100 μg, n = 5). Each heifer received a single injection of the appropriate steriod on Day 8, 9, 10, 11 or 12 post estrus. Jugular venous blood samples were collected at frequent intervals for 24 h to quantify testosterone, and then daily for 14 d to quantify progesterone. Concentrations of testosterone increased within 15 min of injection of testosterone, and reached a maximum at 30 min. Concentrations were maintained at > 2 ng/ml throughout the first 24 h after injection. Based on concentrations of progesterone, neither androgen had any effect on the lifespan of the corpus luteum or the level of luteal function.

Regulation of blood flow to the rabbit corpus luteum: effects of estradiol and human chorionic gonadotropin.

We tested the hypothesis that estrogen and hCG can modify blood flow in the rabbit corpus luteum. Radioactively labeled microspheres were used to measure luteal blood flow in pseudopregnant rabbits in which estrogen had been withdrawn to initiate premature luteal regression and in pseudopregnant rabbits injected with hCG. Removal of estradiol-filled Silastic capsules on day 10 of pseudopregnancy caused an 80% decrease in the serum progesterone concentration within 24 h. Despite the decline in progesterone secretion, luteal blood flow remained at very high levels and was not different from that in control rabbits treated continuously with estradiol. Replacement of estradiol-filled capsules for 3 h did not change the high rate of blood flow to the corpus luteum, but blood flow in the uterus, vagina, and ovarian stroma was increased. The injection of hCG (10 IU, iv) on day 10 of pseudopregnancy caused a 3-fold increase in blood flow to the nonluteal portion of the ovary and a 3-fold increase in the serum progesterone concentration, but luteal blood flow did not change. We conclude that the acute actions of estradiol or hCG in the rabbit corpus luteum are not mediated by changes in luteal blood flow. Further, the results suggest that the luteal vasculature is regulated differently from the vasculature of other estrogen-responsive tissues and that blood flow in the nonluteal tissues of the ovary can be regulated independently of blood flow in the corpus luteum.

Changes in the plasma concentrations of inhibin throughout the normal sheep oestrous cycle and after the infusion of FSH

A radioimmunoassay for inhibin was developed using a peptide containing the 1-26 amino acid sequence of the N-terminus of the alpha-chain of 32 kDa porcine inhibin as immunogen, and 125I-labelled tracer. Evaluation of this assay using Sephadex column chromatography, chromatoelectrophoresis and immunoblotting confirmed that it measured all forms of inhibin present in sheep follicular fluid and was suitable for measurement of inhibin in sheep plasma. There was no evidence of the presence of free alpha-subunit in either sheep follicular fluid or ovarian vein plasma. The concentration of inhibin in jugular plasma throughout the follicular and luteal phases of four ewes with ovarian autotransplants was measured. The ovarian secretion of inhibin and oestradiol were also measured simultaneously throughout the follicular phase in a spontaneous cycle and after infusion of NIH-oFSH-S14 at 10 micrograms/h for 48 h following premature luteal regression induced by prostaglandin. The results showed: (1) no change in the peripheral concentration of inhibin throughout the cycle except an increase related to the periovulatory increase in FSH and LH. (2) Following luteal regression, the concentration of FSH fell as the secretion rate of oestradiol increased. During this time there was no significant change in the peripheral concentration of inhibin or ovarian inhibin secretion rate. (3) Following the infusion of FSH there was a marked increase in the concentration of inhibin in both ovarian and peripheral plasma and an increase in ovarian inhibin secretion rate. (4) The calculated metabolic clearance rate of inhibin, 20.3 ml/min, is similar to that of FSH. We conclude that in the ewe the ovarian inhibin secretion rate is stimulated by FSH and, although inhibin may modulate the basal secretion of FSH, a change in its secretion does not account for the fall in FSH which occurs during the follicular phase of the sheep oestrous cycle.

Inhibin secretion by the sheep ovary during the luteal and follicular phases of the oestrous cycle and following stimulation with FSH.

The secretion of oestradiol and inhibin were measured during the follicular and luteal phase of the cycle by a sensitive bioassay using sheep pituitary cells in culture in four ewes in which the left ovary had been autotransplanted to the neck. On day 12 of the cycle, premature luteal regression was induced with an injection of 100 micrograms cloprostenol (prostaglandin F2 alpha analogue; PG) and ovarian venous blood was collected every 4 h for 72 h. These same four ewes were infused in the ensuing cycle with NIH-oFSH-S14 at 10 micrograms/h for 48 h immediately after an injection of PG and sampled as above. During the luteal phase (-2 h before PG) both in the control and FSH-infused cycles the inhibin secretion rate (SR) was 27-45 units/min. After PG injection, the inhibin SR declined with time to reach 3.6-5 units/min at the onset of the LH surge (60 h after PG) in the control cycle. In contrast, in the following cycle infusion of FSH after PG injection caused a slight increase in the inhibin SR which then remained raised at 42-50 units/min for up to 60 h after PG. In the late follicular phase the oestradiol SR was greater in the FSH-infused than in the control cycles, indicating multiple follicular development. In the FSH-infused cycle the preovulatory surges of LH and FSH were markedly attenuated. These data demonstrate that (1) inhibin SR is high during the luteal phase suggesting that the sheep corpus luteum secretes inhibin, (2) in the control cycle inhibin SR declines during follicular maturation at a time when oestradiol SR is increasing but FSH levels are decreasing, and (3) exogenously administered FSH stimulates the secretion of inhibin from the ovary during the follicular phase.

Estrogen Induces Premature Luteal Regression in Rhesus Monkeys during Spontaneous Menstrual Cycles, but Not in Cycles Driven by Exogenous Gonadotropin-Releasing Hormone

Estrogen Induces Premature Luteal Regression in Rhesus Monkeys during Spontaneous Menstrual Cycles, but Not in Cycles Driven by Exogenous Gonadotropin-Releasing Hormone

Estrogen Induces Premature Luteal Regression in Rhesus Monkeys during Spontaneous Menstrual Cycles, but Not in Cycles Driven by Exogenous Gonadotropin-Releasing Hormone

Estrogen Induces Premature Luteal Regression in Rhesus Monkeys during Spontaneous Menstrual Cycles, but Not in Cycles Driven by Exogenous Gonadotropin-Releasing Hormone

Estrogen induces premature luteal regression in rhesus monkeys during spontaneous menstrual cycles, but not in cycles driven by exogenous gonadotropin-releasing hormone.

Administration of exogenous estradiol during the mid- to late luteal phase of the menstrual cycle results in premature regression of the corpus luteum. The present study was initiated to identify the site of action of estrogen as well as to determine why administration of estrogen during the early luteal phase of the menstrual cycle does not result in luteolysis. Based upon extant literature, we hypothesized that estrogen and progesterone synergize to promote premature luteal regression. We tested this hypothesis in intact, spontaneously cycling rhesus monkeys by inserting estradiol, progesterone, or estrogen plus progesterone capsules on days 2 through 6 of the luteal phase. Insertion of estrogen or progesterone capsules alone did not advance luteolysis compared with the effect of control empty implants (n = 3). In contrast, insertion of estrogen plus progesterone implants on days 2 through 6 of the luteal phase resulted in a significant lowering of serum progesterone concentrations, and menses was advanced 5-6 days compared with control cycles. On the basis of these findings in spontaneously cycling monkeys, we speculated that estrogen treatment causes luteal regression only in the presence of a progesterone-mediated decrease in LH pulse frequency. To test this hypothesis, we used rhesus monkeys whose endogenous gonadotropin secretion was abolished by either placement of radiofrequency lesions in the mediobasal hypothalamus or transection of the hypothalamic-pituitary stalk. Ovulatory menstrual cycles were restored by pulsatile administration of exogenous synthetic GnRH. Insertion of estradiol capsules during the luteal phase into animals whose gonadotropin pulse frequency was set at either one pulse per h or one pulse per 8 h failed to cause premature luteal regression (n = 4). These findings indicate that whereas estrogen promotes luteal regression in intact, spontaneous cycling rhesus monkeys, it does not do so in animals whose gonadotropin secretion is controlled by exogenous GnRH. On the basis of these observations, we conclude that the hypothalamus is a major site of action of estrogen in the initiation of luteal regression in macaques.

Induction of menstruation by antiprogesterone ZK 98.299 in cycling bonnet monkeys

The antiprogestin ZK 98.299 (11β-(4-dimethylaminophenyl)-17α-hydroxy-17β -(3-hydroxypropyl)-13 α-methyl-4,9-gonadien-3-one) was administered s.c. (30 mg/day) to two groups of cycling bonnet monkeys. In Group I (n = 6), it was injected from day 16 to 18 and in Group II (n = 9) from day 21 to 23 of the cycle. Each animal served as its own control and in the pretreatment cycle the vehicle (benzyl benzoate: castor oil, 1:4) was administered. During the treatment cycle of these animals the peak in estradiol levels was observed between days 8 to 11 of the menstrual cycle. In Group I animals, administration of ZK 98.299 induced vaginal bleeding in three of the six animals within two days of its first injection. In the remaining three animals the menstrual cycle length was prolonged. However, in all the six animals a premature drop in serum progesterone levels was observed. On the other hand, in Group II in seven animals with ovulatory treatment cycles, administration of ZK 98.299 induced vaginal bleeding within four days of the first dose and significantly shortened the cycle length. A significant decline in progesterone levels was observed in these animals also. However, in two animals in each group, ZK 98.299 induced vaginal bleeding while the serum progesterone levels were still high. Post-treatment cycles were ovulatory but the cycle length was marginally increased in some animals. In two animals of Group II, in which the treatment cycle turned out to be anovulatory, ZK 98.299 did not induce bleeding and had no effect on serum progesterone levels. This study shows that when administered during the luteal phase ZK 98.299 induces vaginal bleeding and premature luteal regression in bonnet monkeys. However, induction of vaginal bleeding may not be associated with drop in progesterone levels. ZK 98.299, therefore, appears to have potential for fertility control which warrants clinical evaluation.

Effects of the antiprogesterone steroid RU 486 during midluteal phase in normal women.

The antiprogesterone steroid RU 486 (17 beta-hydroxy-11 beta-4-dimethyl-aminophenyl)17 alpha(1-propynyl)estra-4,9-dien-3-one) was given orally to 32 normally cycling women for 4 days, starting on the fourth day of the luteal phase. Uterine bleeding occurred on the third day of RU 486 administration in all 14 women treated with 100 mg/day, in 7 of the 8 women treated with 50 mg, and in 8 of 10 women receiving 25 mg/day. Premature luteal regression induced by RU 486 occurred in 8 women treated with 100 mg/day, in 3 treated with 50 mg, and in 2 receiving 25 mg/day. Plasma LH was measured every 15 min from 0800-1200 h for 5 days in 17 women. Mean LH levels decreased and pulsatile release disappeared in 7 of the 8 women treated with 100 mg, in 2 of 4 receiving 50 mg, and in 1 of 5 treated with 25 mg. RU 486 had no effect when given to 5 women with anovulatory cycles for 4 days starting on day 18 of the cycle. 1) RU 486, given to normally cycling women at midluteal phase, provokes uterine bleeding. 2) This effect occurs whether or not luteal regression is induced by the compound, indicating that RU 486 acts directly upon the endometrial tissue, very likely at the progesterone receptor level. 3) The drug may impair simultaneously or separately luteal function and gonadotropin secretion in a dose-dependent manner. 4) The lack of antiglucocorticosteroid activity, at the dosage of 100 mg/day, suggests that RU 486 may be useful for fertility control.

Induction of Ovulation in Seasonally Anovular Ewes by the Introduction of Rams: Effects of Progesterone and Active Immunization Against Androstenedione

The effects of progesterone priming and active immunization against androstenedione on ovulation, oestrus ad premature luteal regression were observed in seasonally anovular Merino ewes which had been induced to ovulate by the introduction of rams. Ovulation was induced in 27 out of 36 ewes, and the response was not affected by either immunization or progesterone priming. The ovulation rate (mean number of ovulations per ewe ovulating) was higher in ewes immune to androstenedione, but there was no significant effect of this treatment on oestrus or luteal maintenance. Priming with progesterone prior to the introduction of rams prevented premature regression of the corpora lutea but had no effect on the other measures of reproductive function. If active immunization were to be applied on a commercial scale, it would not interfere with the practice of mating ewes during the anoestrous season. The increase in ovulation rate in these ewes, with no increase in the proportion of ewes ovulating, indicates that the mechanism for the control of ovulation is separate from that controlling ovulation rate. The mechanism by which progesterone pretreatment prevents premature luteal regression awaits further investigation.

Effect of indomethacin on estrogen-induced luteolysis in the ewe

Three groups of 6 ewes were laparotomized on day 9 of an estrous cycle (estrus = day 0) and the corporà lutea (CL) were marked with India ink. Indwelling cannulae were inserted into the uterine horn adjacent to the CL in groups 2 and 3. Group 1 was injected intramuscularly (i.m.) with corn oil twice daily on day 9. Group 2 received 750 ug 17β-estradiol (E 2) i.m. twice daily on day 9 plus intrauterine injections of indomethacin (INDO) vehicle on days 9 through 13. Group 3 received the same estrogen treatment plus the injection of 20 mg INDO twice daily on days 9 through 13. Jugular venous samples were taken once daily on days 9 through 14 progesterone analysis. At re-laparotmy on day 14, the ovaries were examined for new ovulations, and the ovary bearing the marked CL was removed. Results showed that E 2 induced premature luteal regression as indicated by decreased CL weights and plasma progesterone levels. INDO when given in conjuction with E 2 effectively blocked the luteolytic action of E 2. These results suggest that the luteolytic action of E 2 is mediated via increased prostaglandin secretion and release from the uterus.

Role of the uterus in oestradiol-induced luteal regression in the ewe.

A single injection or two consecutive daily injections of oestradiol into intact ewes from Days 9 to 13 of the oestrous cycle induce premature luteal regression (Stormshak, Kelley & Hawk, 1969; Hawk & Bolt, 1970; Howland, Akbar & Stormshak, 1971). If the ewes are hysterectomized on Days 5 or 9 of the cycle, oestradiol administered between Days 9 and 13 does not cause regression of the CL, suggesting an involvement of the uterus in the effect of oestradiol on the CL (Stormshak et al., 1969; Bolt & Hawk, 1975). It has been proposed that the uterine luteolysin in the ewe is prostaglandin F-2α (McCracken et al., 1972), and oestradiol injection on Days 9 and 10 of the cycle results in an increased concentration of prostaglandin F-2α in uterine venous plasma 18 hr after the last injection (Ford et al., 1975).

Effect of intra-uterine beads alone, or combined with oestrogen treatment, on utero-ovarian venous plasma prostaglandin F2alpha and progesterone levels in the guinea-pig.

The presence of beads in the guinea-pig uterus caused premature regression of the corpora lutea, and a corresponding decrease in utero-ovarian venous plasma levels of progesterone, by days 9-10 of the oestrous cycle. If the beads were placed in one horn only, premature luteal regression occurred only in the adjacent ovary. Induced luteal regression was preceded by an increased release of prostaglandin F2alpha (PGF2alpha) from the uterine horns which contained the beads. Oestradiol benzoate treatment of guinea-pigs carrying beads in one uterine horn overcame the unilateral effect and resulted in premature luteal regression in both ovaries. This was also associated with the early release of PGF2alpha from both uterine horns, though a difference in the timing of the release was apparent between the bead-containing (experimental) and control horns.

Ewe luteal function influenced by pulsatile administration of synthetic LHRH/FSHRH.

The influence of repetitive administration of synthetic LHRH/FSHRH or saline (S) on 17beta-estradiol (E2)-induced precocious luteal regression in the ewe was examined. Ewes were pre-treated on days 10 and 11 of the estrous cycle with either 750 mug E2 (total dose = 1.5 mg) in oil or with oil (O) alone. Treatment involved in delivery of 10 mug of synthetic LHRH/FSHRH in saline or an equal volume of saline only, administered at 2-h intervals beginning on day 12 of the estrous cycle and continuing through the succeeding 72 hours. During the period of LHRH administration, the serum LH patterns in the O-LHRH and E2-LHRH groups were characterized by rhythmic fluctuation, rising in response to LHRH and falling prior to the subsequent treatment injection. Throughout the course of the treatment period, the serum LH levels in the O-LHRH group were consistently higher than those in the E2-LHRH group. No increase in serum LH concentration was observed in the saline-treated animals. The mean luteal weight and mean luteal progesterone content at the end of the 72-h period were not significantly different between the O-S and E2-LHRH groups (543 +/- 88 vs. 455 +/- 126 mg and 13.1 +/- 6.2 vs 16.0 +/- 9.7 mug, respectively). Both luteal weight and progesterone content were increased (P less than .01) in the O-LHRH group (1089 +/- 87 mg and 47.5 +/- 3.1 mug) and significantly reduced (P less than .05) in the E2-S group (309 +/- 49 mg and 5.2 +/- 0.1 mug) compared with those of either the O-S group or the E2-LHRH group. Thus LHRH treatment increased mean luteal weight and mean luteal progesterone content while E2 pre-treatment depressed the same parameters. These data suggest that pulsatile administration of synthetic LHRH is able to elevate serum LH levels to an extent sufficient to counteract both natural luteolysis and premature luteal regression induced by E2 treatment.

CHANGES IN PLASMA LEVELS OF PROLACTIN AND LH INDUCED BY LUTEOLYTIC OR LUTEOTROPHIC TREATMENT IN INTACT CYCLING SHEEP AFTER SECTION OF THE PITUITARY STALK

ABSTRACT Oestradiol has been shown to cause either premature luteal regression or prolonged luteal maintenance depending on whether it is administered early or late in the oestrous cycle. Although these effects are not observable in the absence of the uterus, it was considered desirable to examine the possibility that the pituitary gland as well as the uterus may be involved in this phenomenon. Accordingly, plasma LH and prolactin concentrations were studied in sheep treated with oestradiol from day 3 (luteotrophic action) or day 11 (luteolytic action) with and without pituitary stalk section. Plasma LH fell below the limit of detection (0.3 ng/ml) in the plasma of sheep after pituitary stalk section, whether or not oestradiol had been administered. In the intact ewe, oestradiol given from day 3 resulted in luteal maintenance associated with a significant increase in the secretion of plasma LH and prolactin. However, similar treatment in the stalk sectioned ewe also resulted in luteal maintenance without any major increase in gonadotrophin secretion. On the other hand, when oestradiol was given from day 11, there was no evidence either from the intact or the stalk sectioned sheep that the pituitary contributed to the luteolytic action of oestradiol may possibly have a pituitary component, the luteolytic action is probably mediated solely by the oestrogenic action on the uterus.

The relationship between the uterus and ovaries during early pregnancy in the guinea-pig.

SUMMARY In mated guinea-pigs one uterine horn was rendered sterile by ligation of the oviduct 2 or 3 days after finding spermatozoa in the vaginal smear. Two glass beads were inserted into the sterile horn on each of days 3–12 and on day 14 in experimental animals but not in controls. At autopsy on day 20 large corpora lutea were present in both ovaries of the control animals. The presence of beads that had been introduced on days 3 and 4 and on days 10–14 resulted in marked regression of the corpora lutea in the adjacent ovary, in the absence of a decidual reaction in the uterus, while luteal enlargement typical of pregnancy occurred in the contralateral ovary. Beads inserted on days 5–8 caused decidualization in the sterile horn but did not induce premature luteal regression in the ipsilateral ovary.