Normal Luteal Phase Research Articles

Analysis of the bleeding pattern in assisted reproduction cycles with luteal phase supplementation using vaginal micronized progesterone

This study was designed to determine the effects of a vaginal micronized progesterone preparation on bleeding patterns and pregnancy outcomes after in-vitro fertilization and intracytoplasmic sperm injection (IVF-ICSI). The study population consisted of 149 consecutive women who had undergone IVF-ICSI using 'long-protocol' stimulation with buserelin-human menopausal gonadotrophin (HMG). A retrospective chart analysis of computerized medical records was undertaken. Vaginal progesterone (200 mg three times daily) was begun the day before oocyte retrieval and continued for a minimum of 16-19 days following human chorionic gonadotrophin (HCG) administration. Occurrence of bleeding following HCG injection, pregnancy rate and outcomes, and serum concentrations of oestradiol were measured. Women undergoing IVF and embryo transfer with ICSI and using vaginal progesterone for luteal support had normal luteal phase lengths (day of HCG minus day of onset of bleeding). In the absence of pregnancy, bleeding occurred after 19.2 +/- 3.9 days (mean +/- SD). Out of the pregnant group only three women bled within 19 days of HCG administration: two had biochemical pregnancies which spontaneously vanished and one evolved to term. The results reflect the normal bleeding pattern to be expected when vaginal progesterone is used for luteal support in IVF and embryo transfer, an approach whose efficacy has been amply proven. No shortened luteal phases were observed using vaginally administered progesterone.

Effects of progesterone receptor blockers on human granulosa-luteal cell culture secretion of progesterone, estradiol, and relaxin.

We have developed culture methods for human luteinizing granulosa cells (GLC) that support the timely and dynamic secretion of estrogen (estradiol-17beta; E(2)), progesterone (P(4)), and relaxin (Rlx) in patterns that mimic serum hormone concentrations during the luteal phase of the menstrual cycle. Additional hCG, to simulate rescue of the corpus luteum, prevented the normal decline in GLC hormone production. To test the importance of the P(4) receptor in P(4) production, GLC were treated in vitro with two P(4) receptor antagonists. Human GLC received one of two hCG support protocols: a Baseline group simulating the normal luteal phase or a Rescue group simulating early pregnancy. Baseline and Rescue groups were treated with either RU-486 or HRP2000 either early or late in the cell culture period. The effects of treatments or control on ovarian steroid and peptide hormone production were determined (significant difference was P < 0.05). In the Rescue group, late treatment resulted in an immediate and dramatic decline in E(2), P(4), and Rlx secretion to nearly nondetectable levels within 1 day after treatment, and hormones remained depressed for the remaining 10 days of culture. In contrast, early treatment resulted in a decline in steroid hormone secretion that returned to control levels within 5 days of cessation of treatment, and Rlx secretion was delayed for approximately 5 days more than in controls. The data support the hypothesis that P(4) may be a required autocrine factor, not only for its own production but also for the maintenance of full endocrine function of the corpus luteum.

The effect of bovine somatotropin (bST) administration on reproduction, progesterone concentration during lactation and LH secretion during estrus, in dairy ewes

Twenty-two polytocous lactating Chios ewes were used to test the effects of bovine somatotropin (bST) on reproduction, progesterone concentration and LH secretion during estrus. Half of the ewes were injected every second week with 160 mg bST in a prolonged release vehicle, from the fifth day post partum until the end of lactation, while the remaining ones were used as controls. All animals were fed the same amount of ration. Supplementation with bST resulted in an increase of milk production (P<0.05) and an insignificant trend for delayed resumption of normal estrous cycles. Although there were no differences between groups, there was also a tendency for the bST group to display lower progesterone concentrations during the first three fortnights after the onset of normal estrous cycles and higher ones during the last three fortnights of the experiment, compared with the control group. Duration of the first normal luteal phase after delivery of the bST group was found to be shorter compared with the control group (P<0.05). After estrous synchronization the bST group showed a shorter estrus compared with the control group (P<0.05). Average and baseline LH concentrations during synchronized estrous in the bST group was lower (P<0.001) compared with the control group. Additionally, the conception rate did not differ between the two groups. This study supports the concept that the beneficial effects of bST treatment on milk production outweigh the potential deleterious effects on reproduction.

Platelet-activating factor may act as an endogenous pulse generator for sheep of luteolytic PGF2alpha release.

Pulsatile release of uterine prostaglandin F2alpha (PGF2alpha) induces luteolysis in ruminants. However, the mechanism(s) that initiates and maintains luteolysis has not been defined. The present study tested the hypothesis that the endogenous PGF2alpha pulse generator is uterine-derived platelet-activating factor (PAF). Ovariectomized ewes were given exogenous progesterone (P), estradiol (E), or both (P+E, mimicking the normal luteal phase). Only ewes treated with steroids released PAF into the uterine lumen and had increased PAF:acetylhydrolase activity in the uterine lumen. Steroid treatment also influenced the capacity of the uterus to release PGF2alpha in response to exogenous PAF. PAF infusion did not affect plasma PGF2alpha metabolite (PGFM) levels in control (no steroid treatment) ewes but increased plasma PGFM levels in P+E ewes (P < 0.001) and ewes treated with P or E alone (P < 0.05). Infusion of PAF followed by or coincident with oxytocin (OT) acted in a synergistic manner to increase plasma PGFM levels. Repeated infusion of PAF into the uterus at 1-h intervals induced tachyphylaxis of the PGFM response to PAF; however, sensitivity of the uterus to PAF returned spontaneously by the 6th h. Interferon-tau (IFN-tau) inhibits pulsatile release of PGF2alpha during pregnancy to prevent luteolysis. Exogenous recombinant ovine IFN-tau (50 microgram) inhibited the uterine response to PAF alone or the combined effects of PAF and OT. These results indicate that uterine PAF fulfills many of the criteria for an endogenous PGF2alpha pulse-generator: steroid induction of PAF production and uterine responsiveness to PAF-induced release of PGF; synergistic stimulation of PAF-induced PGF release by OT; inhibition of PAF effects by IFN-tau; and PAF's ability to induce pulses of PGF with a periodicity during a period of chronic exposure of the uterus to PAF.

Effects of time of suckling during the solar day on duration of the postpartum anovulatory interval in Brahman x Hereford (F1) cows.

Previously published reports have indicated that postpartum anovulatory intervals can be markedly reduced and rebreeding performance enhanced in Bos taurus cows by eliminating nighttime suckling. We sought to confirm this hypothesis by examining the effects of day, nighttime, and ad libitum suckling on suckling behavior of calves, duration of the postpartum anovulatory interval, and pregnancy rates in 45 fall-calving Brahman x Hereford (F1) cows. Beginning on d 9 to 12 postpartum, calves were removed from lactating cows from 0700 to 1900 (Night-Suckled, n = 15) or from 1900 to 0700 (Day-Suckled, n = 15), or remained with their dams continuously (Ad Libitum-Suckled, n = 15). Cows in each group were maintained with fertile Angus bulls from d 10 postpartum until the first normal luteal phase or 100 d postpartum, whichever occurred first. Cows were observed for estrous behavior twice daily, and jugular blood samples were collected twice weekly for the determination of serum progesterone concentration. Mean number of suckling episodes per 24 h was greater (P < .0001) for the Ad Libitum-Suckled group than either Night- or Day-Suckled groups (5.9+/-.42 vs 3.8+/-.14, and 3.9+/-.32, respectively). Hourly analysis of suckling episodes in the Ad Libitum group indicated that they were not skewed toward a particular period, with suckling occurring at a periodicity of 4 to 6 h. Intervals to the first rise in progesterone > or = 1 ng/mL (32+/-2.5, 32+/-4.5, and 31+/-1.7 d, respectively), first normal luteal phase (38+/-3.1, 38+/-3.8, and 37+/-2.5 d, respectively), and first estrus (43+/-3.5, 40+/-3.9, and 36+/-1.1 d, respectively) did not differ (P > .05) among the three groups. Similarly, cumulative pregnancy rates within 100 d after calving did not differ (P > .05). These results in Bos indicus x Bos taurus (F1) cattle do not support the previous conclusions in Bos taurus that eliminating nighttime suckling reduces the postpartum anovulatory interval.

Endocrinology of the ovarian cycle and pregnancy in the Asian (Elephas maximus) and African (Loxodonta africana) elephant.

In reviewing the literature, this paper assesses the current level of understanding of the hormonal control of the ovarian cycle and pregnancy in the elephant. Data are compiled from two genera, Elephas maximus and Loxodonta africana, recognizing differences where known to exist. Measurements of various steroid and peptide hormones, but most notably immunoreactive progesterone (iP), indicate an overall cycle length of 15-16 weeks, comprising an 8-11-week luteal phase and a shorter inter-luteal (follicular) period of 4-6 weeks. Oestrogen related phenomena suggest the occurrence of two (possibly more) waves of follicular development with a 3-week periodicity, although oestrogen levels are low and fluctuate without clear pattern. The inter-luteal period is characterized by two discrete LH peaks also 3 weeks apart, but only the second is associated with an iP rise. Ovulation rate is variable and additional luteal structures lacking ovulation points are probably formed each cycle. The post-ovulatory period is associated with elevated progestogen levels, mainly 5alpha-reduced compounds, while progesterone itself is a minor secretory product. A revised model for the elephant ovarian cycle is presented. Detailed information on the endocrinology of pregnancy is lacking. Elevated progestins beyond the normal luteal phase indicate that conception extends the functional lifespan of the CL, with maximum steroidogenic activity between 3-15 months. The nature of the luteotrophic support is not known and placental gonadotrophins have not been conclusively demonstrated. Progestins fluctuate at or slightly above luteal phase values throughout pregnancy. There is a marked increase in prolactin levels after 16-24 weeks and a relationship with oestrogen secretion may exist since circulating and urinary levels show a progressive increase from 6-8 months. A placental contribution to progestin secretion is likely, although direct evidence is lacking. Considerable enlargement of foetal gonads during the second half of pregnancy in African elephants suggests a possible steroidogenic function, but none has been defined. The endocrine events leading to parturition are unknown. In the Asian elephant, a fall in iP precedes parturition; oestrogen levels decline and cortisol increases at the time of birth. The paper concludes with a brief selection of priorities for future research.

Premature elevation in serum insulin-like growth factor-I advances first ovulation in rhesus monkeys.

Previous data suggest that developmental increases in peripheral concentrations of insulin-like growth factor-I (IGF-I) may be one of several neuroendocrine signals that regulate the timing of puberty. In order to test this hypothesis further, normal juvenile female rhesus monkeys (Con; n = 6) were compared with age-matched animals (Igf; n = 4) which received a constant subcutaneous infusion of recombinant human IGF-I (110 micrograms/kg/day) from 18 through 36 months of age. Menstrual bleeding was monitored and ovulation was inferred from a sustained rise in serum progesterone. In order to assess the sensitivity of luteinizing hormone-releasing hormone (LHRH) neurons to excitation, the response of serum LH to the acute administration of the glutamate receptor agonist N-methyl-D, L-aspartic acid (NMDA) was assessed prior to menarche, 2 months following menarche, and during the follicular phase of a female's third ovulation or 50 days after a female's first ovulation. In addition, the pituitary response of LH secretion to an LHRH agonist was assessed during the follicular phase of a female's fourth ovulation or 75 days following her first ovulation. IGF-I treatment effectively elevated serum concentrations by more than 86% of the values observed in Con animals. Although the treatment also enhanced the developmental increase in IGF binding protein-3 (IGFBP-3), IGF-I was increased proportionately more, resulting in a significantly higher molar ratio of IGF-I:IGFBP-3 in treated females throughout the course of the study. Treatment with IGF-I did not affect age at menarche but did significantly advance the age of first ovulation. Consequently, the interval between menarche and first ovulation was significantly shorter in Igf compared with Con females. Although the total number of ovulations exhibited by Igf (3.8 +/- 0.3) and Con females (3.0 +/- 0.5) in the 12 months following menarche was similar, significantly more of these were characterized by normal luteal phase progesterone secretion in Igf (100% +/- 0) compared with Con females (64% +/- 17). An analysis of cycles with a normal luteal phase revealed that serum estradiol during the luteal phase was significantly higher in Igf compared with Con females. Finally, IGF-treated females responded to NMDA treatment with a significantly greater increase in serum LH following menarche but not prior to menarche. In contrast, the response of serum LH to an LHRH agonist did not differ between Igf and Con females. These data suggest that the premature elevation in IGF-I levels, and consequently the ratio of IGF-I:IGFBP-3, accelerates the tempo of the final stages of puberty in rhesus monkeys. This action of IGF-I is probably the result of an increase in LHRH neuronal activity and is not due to a change in pituitary sensitivity to LHRH stimulation. In addition, ovarian sensitivity to LH stimulation during the luteal phase is also increased by IGF-I. Taken together, these data suggest that developmental increases in peripheral IGF-I secretion participate in the neuroendocrine regulation of puberty in female primates.

Protein Degradability and Calcium Salts of Long-Chain Fatty Acids in the Diets of Lactating Dairy Cows: Reproductive Responses

Multiparous Holstein cows (n=45) were assigned at calving to one of four diets arranged in a 2 × 2 factorial design. The two main factors were dietary concentration (dry matter basis) of 1) degradable intake protein (11.1 or 15.7%) and 2) supplemental fat (Ca salts of long-chain fatty acids; 0 or 2.2%). Soybean meal and urea were replaced with less degradable protein meals (corn gluten meal, meat and bone meal, fish meal, and blood meal). During the first 9 wk postpartum, cows fed diets containing the greater concentration of highly degradable protein demonstrated less follicular development on their ovaries, were delayed in their first luteal activity postpartum (25.2 vs. 38.6 d), accumulated less luteal tissue (<15 vs. >70mm), and had lower plasma progesterone accumulated over time. The supplementation of Ca salts of long-chain fatty acids to the 15.7% degradable protein diet doubled the number of corpora lutea, reduced time to first rise in progesterone by 6 d, doubled the number of normal luteal phases, and restored the pattern of accumulated plasma progesterone concentrations to a pattern that was similar to that induced by other diets. Cows were synchronized to estrus and inseminated at approximately 65 d postpartum. Pregnancy rate was increased from 52.3 to 86.4% when fat was supplemented. Cows fed fat tended to have more corpora lutea and a larger corpus luteum and accumulated more plasma progesterone than did cows not fed fat. Diets containing excess degradable protein or Ca salts of long-chain fatty acids influenced ovarian structures and reproductive performance.

Simulation of human luteal endocrine function with granulosa lutein cell culture.

Human granulosa cells collected from in vitro fertilization have previously been cultured to provide a system to simulate the granulosa lutein cells of the corpus luteum. In most of these systems, the cultures have been relatively short term, and attempts to simulate the normal pattern of hormone production observed during the luteal phase of the cycle have not been reported. Additionally, the hormone relaxin has generally been absent from the endocrine analysis of these systems. In this report, methods were used that supported secretion of ovarian steroids and relaxin that mimics the profiles of these hormones in vivo. This system was used to observe the endocrine responses of the granulosa lutein cells to three different protocols of CG administration designed to mimic the normal luteal phase, early pregnancy, and early pregnancy followed by pregnancy loss. The normal luteal phase was simulated by a constant baseline (0.02 IU/mL) CG model to simulate a nonconceptive cycle (baseline). The second model was baseline CG until day 8 of culture, followed by daily doubling from days 9-17 to simulate an early pregnancy (rescue-plateau). CG concentrations were then held constant from days 17-20 (5.12 IU/mL). A third model (rescue-drop) was used that was identical to the early pregnancy model except that on day 17 CG was returned to baseline concentrations (0.02 IU/mL) to simulate an early pregnancy loss. Baseline CG stimulation resulted in profiles of estrogen, progesterone, and relaxin secretion in culture that were closely related to secretory profiles previously reported in serum during the nonconceptive luteal phase. The timing of appearance of relaxin secretion and later declines in steroid and relaxin secretion paralleled that observed in serum. In the CG rescue protocols, ovarian steroids rose in response to daily doubling of CG and fell when CG either plateaued or fell. Relaxin did not show an increase in response to increasing CG, but its secretion did not drop when CG concentrations plateaued or dropped. This cell culture system model mimics the profile of ovarian steroids and relaxin seen in serum during the nonconceptive luteal phase, although the relative magnitude of the hormones was not the same as seen in vivo. It was also used to investigate responses to luteal rescue protocols designed to simulate early pregnancy and pregnancy loss. This culture system may be useful to study differences in endocrine response in granulosa cells collected from different patients and to provide information of clinical relevance. This culture system provides a model to study luteal function and its response to different protocols of luteal rescue and thus may provide insight into early pregnancy and pregnancy loss.

Intensive hormone monitoring in women with unexplained infertility: evidence for subtle abnormalities suggestive of diminished ovarian reserve

Objective: To determine hormone levels across the menstrual cycle in women with rigorously defined unexplained infertility. Design: Prospective study. Setting: National Center for Infertility Research at Michigan. Patient(s): Evaluation of 1,885 women with infertility identified 12 women who met the following rigorously defined criteria for unexplained infertility: [1] infertility of ⩾24 months' duration, with no male factor, anatomic or functional disorders of the reproductive tract, or immunologic infertility; [2] normal body mass index (BMI); (3) ovulatory cycles ranging from 26 to 32 days; [4] normal luteal phase determined by endometrial biopsy; and [5] normal baseline hormonal profile. Controls (n = 12) were healthy, parous women with normal ovulatory cycles and normal hormonal screens, and were matched for age and BMI with patients. Main Outcome Measure(s): Daily gonadotropin and steroid hormone levels across the menstrual cycle. Result(s): Basal FSH and LH levels in the early, middle and late follicular phases were increased significantly in the group with unexplained fertility compared with the normal controls. The mean (±SD) early follicular FSH levels were 7.0 ± 0.57 mIU/mL in the unexplained-infertility group and 4.7 ± 0.37 mIU/mL (conversion factor to SI units, 1.00) in the normal controls, respectively. There was no difference between groups over the periovulatory or luteal phase. Midluteal mean (±SD) P levels were lower in the unexplained-infertility group than in the normal controls (13.7 ± 1.6 versus 24.0 ± 3.2 ng/mL [conversion factor to SI units, 3.180]). Mean E 2 concentrations were elevated in the group with unexplained infertility versus normal controls in the early through the late follicular phase but reached significance only in the midfollicular phase. Mean prolactin levels were elevated consistently across the menstrual cycle in the unexplained-infertility group compared with those in normal controls but reached significance only in the early and late follicular and midluteal phases of the cycle. Cortisol concentrations were similar between the two groups. Conclusion(s): These data indicate that there are subtle alterations in various hormones measured across the menstrual cycle in women with unexplained infertility compared with those in normal controls, suggesting a diminished ovarian reserve.

Modulation of airway reactivity and peak flow variability in asthmatics receiving the oral contraceptive pill.

Female sex-steroid hormones may play an important influence in asthma. The aim of this study was to compare airway reactivity to adenosine monophosphate (AMP) in female asthmatics with natural menstrual cycles and those taking the oral combined contraceptive pill (OCP). Eighteen asthmatic subjects were evaluated. Nine subjects, mean (SEM) age, 24 (6) years, FEV1 93% (10) predicted, with natural cycles (group 1) were compared with nine subjects, age 24 (6) years, FEV1 93% (9) predicted taking the OCP (group 2). Group 1 subjects were evaluated at the follicular (visit 1) and luteal (visit 2) phases; group 2 subjects were evaluated during the week off OCP (visit 1) and at the end of the OCP cycle (visit 2). At each visit, serum progesterone and estradiol were measured. Airway reactivity to AMP was evaluated and expressed as PC20 (FEV1; mg/ml). Morning and evening peak expiratory flow rates (PEFR) were monitored throughout the study. In group 1, there was a significant increase in serum progesterone (nmol/l) and estradiol (pmol/l). (Visit 1 vs. 2): 2.5 vs. 13.5 (95% CI 2.1 to 19.9; p = 0.02) and 152.3 vs. 358.1 (95% CI 113.0 to 298.5; p < 0.001), respectively. In group 2, however, there was no increase between visit 1 vs. 2 in hormones: 0.9 vs. 1.0 and 75.7 vs. 21.8 for progesterone and estradiol, respectively. There was a significant increase in airway reactivity in group 1 during the luteal phase. Geometric mean PC20 (mg/ml) was 18.8 and 4.7 at visit 1 and 2, respectively: a 4.0-fold difference (95% CI 1.25 to 13.03; p = 0.03) amounting to two doubling doses. In contrast, there was no change in PC20 in group 2. Geometric mean PC20 was 23.5 and 21.4: a 1.06-fold difference (95% CI 0.41 to 2.78; p = 0.83). In group 1, morning and evening PEFR (l/min) were significantly different at both visits: at visit 1 (A.M. PEFR vs. P.M. PEFR) 403 vs. 430 (95% CI 5 to 50; p < 0.001) and visit 2, 415 vs. 439 (95% CI 1 to 46; p < 0.001). In group 2, there was no significant difference in diurnal PEFR variability at both visits; 411 vs. 417 at visit 1 and 413 vs. 427 at visit 2. In conclusion, asthmatic patients receiving the OCP had attenuated cyclical change in airway reactivity as well as reduced diurnal PEFR variability, which was associated with suppression of the normal luteal phase rise in sex-hormones.

Unexplained infertility: Evaluation of the luteal phase; results of the National Center for Infertility Research at Michigan

To evaluate the luteal phase in women with rigorously defined unexplained infertility. Prospective study. National Center for Infertility Research at Michigan. Evaluation of 1,885 women with infertility identified 12 women who met the rigorously defined criteria for unexplained infertility: [1] infertility of > or = 24 months duration, with no male factor, anatomic-functional disorders of the reproductive tract, or immunologic infertility; [2] normal body mass index (BMI); [3] ovulatory cycles ranging from 26 to 32 days; [4] normal luteal phase determined by endometrial biopsy; and [5] normal baseline hormonal profile. Controls (n = 12) were healthy, parous women with normal ovulatory cycles, normal hormonal screen, and were matched for age and BMI to patients. Pattern of follicular growth rate and luteal phase hormonal profile. Women with unexplained infertility did not differ in menstrual cycle characteristics, follicular growth rate or mean preovulatory follicle diameter, or endometrial biopsy dating. The mean levels of P tended to be lower in the unexplained infertility group throughout the luteal phase, but only the midluteal interval reached statistical significance. Luteal phase mean integrated P or urinary PDG levels of unexplained infertility women did not differ from those of fertile controls. The ratio of integrated E2:P also was significantly greater in women with unexplained infertility than in fertile controls. Women with rigorously defined unexplained infertility have subtle hormonal anomalies during the luteal phase when compared with fertile controls.

Single luteal phase serum progesterone assay as an indicator of ovulation

The availability of a rapid, accurate serum progesterone assay would alleviate many of the problems of patient inconvenience and discomfort encountered with the classical methods of ovulation detection. With the use of a competitive protein binding technique, by which a single technician can assay 30 or more samples for serum progesterone in one day, a range of daily follicular and luteal phase values was ascertained in a group of normally menstruating women. After a normal luteal phase range was established, single luteal phase serum progesterone sampling was performed in 51 infertile women with regular menses and 35 oligomenorrheic women undergoing clomiphene therapy. In the follicular phase of the cycle, progesterone levels were consistently less than 2 ng. per milliliter. Between 11 and 4 days prior to the onset of menses, in presumptively ovulatory cycles, serum progesterone levels were always 3 ng. per milliliter or greater. Progesterone values in this range were always accompanied by a secretory endometrium and, thus, can be considered presumptive evidence of ovulation.

Will treatment with progesterone, either alone or with oestradiol result in behavioural oestrus and a normal length luteal phase in postpartum beef suckler cows induced to ovulate by calf isolation and once-a-day suckling?

In beef suckler cows, the prolonged interval from calving to first ovulation (post-partum interval, PPI) is due to failure of ovulation of dominant follicles. It appears that a combination of poor body condition, maternal calf-bond and suckling act to suppress the LH pulse frequency necessary for ovulation. A combination of calf isolation and once-a-day suckling can significantly shorten the PPI, but the first ovulation generally occurs without overt oestrus and the subsequent cycle is short (8 to 11 days) due to lack of progesterone priming. The aim of this study was to examine the effects of progesterone or progesterone and oestradiol in conjunction with calf isolation on the interval to first ovulation, incidence of overt oestrus at first ovulation and length of the subsequent interovulatory interval.

Expression of tissue inhibitor of metalloproteinases-1 in the primate ovary during induced luteal regression.

Although tissue inhibitor of metalloproteinases-1 (TIMP-1) is one of the major secretory products of the corpus luteum, the functional significance of this is not clear. In addition to its role as a specific inhibitor of the matrix metalloproteinase enzymes involved in tissue remodelling, it has recently been suggested that TIMP-1 is also a potent stimulator of steroidogenesis in vitro. However, in the ruminant, TIMP-1 expression increases during luteal regression. This study sought to determine (i) the effect of induced luteal regression on ovarian TIMP-1 expression in the primate and (ii) the expression of TIMP-1 in other steroidogenic and non-steroidogenic tissues. Marmoset ovaries were studied on day 10 of the normal luteal phase and 12 and 24 h after induced luteolysis, with either gonadotrophin-releasing hormone (GnRH) antagonist or prostaglandin F2 alpha analogue. Ovaries from different stages of the normal ovarian cycle were also studied. Expression of TIMP-1 was investigated by isotopic in situ hybridisation. TIMP-1 expression was also examined in a wide range of other marmoset tissues by Northern blotting and in situ hybridisation. TIMP-1 was found to be highly expressed in the marmoset corpus luteum. Luteolysis induced with either prostaglandin F2 alpha or GnRH antagonist was associated with a significant fall in TIMP-1 expression in luteal tissue. TIMP-1 mRNA was also localised to ovarian follicles throughout the ovarian cycle. Expression occurred in the thecal layer of smaller follicles (< 1.5 mm) and the granulosal layer of larger pre-ovulatory follicles. In atretic follicles, TIMP-1 was highly expressed at the interface between the thecal and granulosal cells. TIMP-1 was found to be predominantly expressed in steroidogenic tissues, particularly the ovary, adrenal and placenta. These data support a role for changes in TIMP-1 expression in tissue remodelling in the ovary and are consistent with an additional function of TIMP-1 as a facilitator of steroidogenesis.

Luteinizing hormone receptor in the human corpus luteum: lack of down-regulation during maternal recognition of pregnancy.

Luteal progesterone production is dependent on luteinizing hormone (LH) from the pituitary gland. Despite continuing LH secretion, the human corpus luteum undergoes functional luteolysis unless it is 'rescued' by human chorionic gonadotrophin (HCG), produced by the implanting blastocyst. As LH and HCG act through a common receptor, this study sought to determine the expression of the LH/ HCG receptor in the corpus luteum during maternal recognition of pregnancy. Corpora lutea were collected at hysterectomy from women in the normal luteal phase and after luteal 'rescue' with exogenous HCG. In each case the corpus luteum was classified according to the date of the LH surge measured in daily urine samples. The expression of the LH receptor was investigated by Northern blotting, in-situ hybridization and in-situ ligand binding. LH receptor mRNA and ligand binding activity were detected in corpora lutea from all stages of the luteal phase. LH receptor expression and binding were maintained during maternal recognition of pregnancy in the presence of exponentially increasing HCG concentrations. These data show that the LH receptor is maintained throughout the functional life-span of the human corpus luteum and is not down-regulated during maternal recognition of pregnancy.

Effect of continuous infusion of thyrotrophin-releasing hormone on plasma prolactin and on ovarian activity in melatonin-treated ewes.

Twelve anoestrous ewes maintained under natural photoperiod at 57 degrees N received an oral dose of 3 mg melatonin daily at 15:00 h from 1 May. Starting 41 days later and extending from 11 June until 5 September, six of the ewes were also infused continuously with 0.8 mg thyrotrophin-releasing hormone (TRH) day-1 via subcutaneous osmotic minipumps. The remaining six ewes acted as controls. Behavioural oestrus, ovulation rate and luteal function were determined by exposure to a vasectomized ram, laparoscopy and the measurement of progesterone in peripheral plasma, respectively. TRH infusion stimulated a sustained increase (P < 0.001) in plasma concentrations of thyroxine, tri-iodothyronine and prolactin (thyroxine: 158 +/- 9.3 and 65 +/- 7.7 nmol l-1 for TRH-infused and control ewes, respectively; tri-iodothyronine, 2.6 +/- 0.12 and 1.1 +/- 0.19 nmol l-1 and prolactin, 57 +/- 12 and 11 +/- 2 micrograms l-1). No ewes were in oestrus before TRH infusion and the mean number of behavioural oestrous cycles per ewe during the infusion period was 1.3 +/- 0.33 and 2.5 +/- 0.34 for TRH-infused and control ewes, respectively (P < 0.05). Corresponding mean intervals from 1 May to the onset of the first luteal phase (progesterone > 1 ng ml-1) were 88 +/- 8.9 and 79 +/- 3.5 days (not significant). TRH infusion had no effect on the mean numbers of corpora lutea (1.7 +/- 0.14 and 1.6 +/- 0.20 for TRH-infused and control ewes, respectively), but was associated with a lower mean incidence of normal luteal phases (1.5 +/- 0.43 versus 2.7 +/- 0.21, P = 0.052). Abnormalities in luteal function included delayed initial expression, extended ovarian cycles, suprabasal periovulatory progesterone concentrations and protracted periods of low progesterone secretion between successive ovarian cycles. Thus continuous TRH infusion suppressed plasma prolactin, doubled the circulating concentrations of thyroxine and tri-iodothyronine, and was associated with a wide range of abnormalities in ovarian function and endocrine status, the nature of which varied between ewes.

Effects of exogenous oxytocin and progesterone on GnRH-induced short luteal phases in anoestrous ewes.

Two experiments investigate the effects of oxytocin and progesterone on premature luteolysis in ewes. In Expt 1, 20 anoestrous ewes were induced to ovulate by multiple injections of GnRH (250 ng i.v. every 2 h for 24 h) followed by a bolus injection of GnRH (125 micrograms, i.v.). Ten ewes received a continuous infusion of oxytocin from the day after the GnRH bolus injection and the other ten ewes were infused with saline. Oxytocin infusion had no significant effect on the proportion of ewes with short luteal phases (P > 0.05). All ewes that had luteal phases of normal duration from either group (n = 9) exhibited a transient increase in plasma concentrations of progesterone 2 h after insertion of the pump. In Expt 2, 25 anoestrous ewes were treated with GnRH as in Expt 1. Five ewes were pretreated with progestagen for 11 days and ten ewes received progesterone (12 mg, i.m.) 24 h after the bolus injection of GnRH. All animals received an oxytocin injection (1 microgram, i.v.) on day 4 after the GnRH bolus. All five ewes that were pretreated with progestagen had normal luteal function and none exhibited a 13, 14-dihydro-15-keto PGF2 alpha (PGFM) response to oxytocin. None of the ten ewes injected with progesterone had a normal luteal phase and six ewes exhibited a PGFM response to oxytocin. Four ewes in the control group had normal luteal function and three had short luteal phases. It is concluded that (1) administration of oxytocin from about the time of ovulation does not prevent premature luteal regression; (2) a transient increase in progesterone at about the time of ovulation is associated with luteal phases of normal duration; (3) a more extended exposure to progesterone at about the time of ovulation prevents normal luteal function and may inhibit luteinization and (4) pretreatment with progesterone prevents luteolysis by reducing the uterine response to oxytocin early in the luteal phase.

Serum Lipoperoxide Level Variations in Normal and Luteal Phase Defect Cycles

A luteal phase defect (LPD) is a clinical problem leading to infertility and is characterized by reduced progesterone levels during the luteal phase. Serum lipoperoxidation is an expression of cellular hypoxic damage occurring under all stress-oxidative conditions. Forty-eight consecutive infertility patients, according to the infertility class II of the WHO classification, underwent clinical observation. Twenty-five patients ovulated constantly with a normal luteal phase, while the other 23 had a LPD, hormonally and histologically assessed. The luteal phase was monitored biochemically by titration of progesterone, oestradiol, and serum lipid peroxides during the ovulatory period and 6-12 days after ovulation. The mean plasmatic concentration of oestradiol was not statistically different between the LPD and the normal-cycle groups, while a statistically significant difference was found for progesterone plasmatic concentrations between the LPD and the normal-cycle groups (p < 0.05); a greater statistical difference was also found in the mean serum lipoperoxide titration (p < 0.001). These findings suggest that serum lipoperoxidation titration may be a useful tool in the study of the interactions between hormonal milieu and sympathetic activity.

Exogenous pulses of luteinizing hormone cause persistence of the largest bovine ovarian follicle.

The objectives of this study were, 1) to determine whether increased frequency of LH pulses, independent of changes in progesterone, will cause persistence of the first largest ovarian follicle (LF1) during the bovine estrous cycle and 2) to determine whether a follicle produced in this manner will ovulate after luteal regression. In Exp. 1, 32 nonlactating beef cows were randomized into four groups. Bovine LH was given as 50 micrograms i.v. every 2 h from 0800 on d 7 through 0800 on d 13 postestrus to cows in two groups, which in addition either received PGF2 alpha on d 12 and were allowed to ovulate (LHOV; Group 1) or were ovariectomized (LHOVX; Group 2) on d 13. Cows in Group 3 received progesterone via a used controlled internal drug releasing device (CIDR) on d 4 to 13, PGF2 alpha on d 6, and ovariectomy on d 13. These cows received 1 mL of saline i.v. every 2 h on d 7 to 13, as did those in Group 4 (SAL), but cows in Group 4 did not receive any PGF2 alpha. Proportion (percentage) of LF1 maintained until d 13 was similar in cows with CIDR (100) and on LH (88) but less in cows on SAL (36; P < .01). The LF1 were largest in cows with CIDR, smallest in cows on SAL, and intermediate in cows on LH (P < .001). During d 7 to 13, progesterone was lesser and estradiol was greater in peripheral plasma in cows with CIDR than in cows on LH or SAL (P < .001). In Experiment 2, beef heifers received 50 micrograms of bLH (LH; n = 5) or saline (SAL; n = 4) i.v. every 2 h from 0800 on d 7 until 12 h after signs of estrus were observed following PGF2 alpha on d 12. The LF1 were maintained by LH and 60% ovulated; all LF1 were replaced during treatment in heifers on SAL. The LF1 were larger in heifers on LH, but estradiol and progesterone did not differ between groups. In conclusion, an increased frequency of LH pulses during a normal luteal phase allowed LF1 to persist but did not increase secretion of estradiol.