Preovulatory Luteinizing Hormone Peak Research Articles

Impact of adrenocorticotropin hormone administration on the endocrinology, estrus onset, and ovarian function of weaned sows.

Chronic stress affects the reproductive health of mammals; however, the impact of adrenocorticotropin hormone (ACTH) level elevation during chronic stress on the reproduction of weaned sows remains unclear. In this study, nine weaned sows with the same parturition date were randomly divided into control group (n = 4) and ACTH group (n = 5). Each group received intravenous administration of ACTH three times daily for 7 days. Blood samples were collected every 3 h after injection. A radioimmunoassay was used to measure the concentrations of cortisol, luteinizing hormone (LH), follicle-stimulating hormone (FSH), progesterone (P4) and estradiol-17β (E2) in the blood. Estrus was determined according to changes in the vulva and the boar contact test. The mRNA expressions of glucocorticoid receptor, FSH receptor, LH receptor (LHR) in the corpus luteum (CL) were detected by qRT-PCR. The results showed that ACTH administration substantially delayed the initiation of estrus and the pre-ovulatory LH peak. The sows of control group ovulated within 10 days and the ovulation rate was 100%, while it was 60% in the ACTH group. Two sows of ACTH group showed pseudo-estrus. The E2 concentrations significantly decreased in the ACTH group at 36 h, 42 h and 66 h of the experimental period. The P4 concentrations in the ACTH group significantly decreased at 132, 138, and 147 h of the experimental period. ACTH significantly reduced the LHR mRNA expression in CLs. In conclusion, long-term repeated ACTH administration affects the endocrinology, estrus onset, and ovarian function of weaned sows.

Interactions of Cortisol and Prolactin with Other Selected Menstrual Cycle Hormones Affecting the Chances of Conception in Infertile Women.

One of the major problems of success in infertility treatment could depend on the understanding how the potential factors may affect the conception. The aim of this study was to evaluate present understanding of such factors or hormonal causes that may induce infertility. We studied the interactions between the two menstrual cycle hormones i.e., cortisol (COR) and prolactin (PRL), along with the ultrasonographic ovulation parameters in a group of N = 205 women with diagnosed infertility. The control group consisted of N = 100 women with confirmed fertility. In both groups, follicle-stimulating hormone (FSH), luteinizing hormone (LH), anti-Müllerian hormone (AMH), thyroid stimulating hormone (TSH), PRL, COR were examined on the third day of the cycle, and estradiol (E2), progesterone (P), and COR were examined during ovulation and 7-days afterwards. In the infertile group, higher levels of PRL and COR were observed than that of in the control group. Cortisol levels at all phases of the menstrual cycle and PRL negatively correlated with E2 secretion during and after ovulation, thus contributed to the attenuation of the ovulatory LH surge. Infertile women who conceived presented with higher levels of E2 during and after ovulation, higher P after ovulation, and thicker endometrium than that of the women who failed to conceive. In conclusion, elevated secretion of COR and PRL in infertile women impairs the menstrual cycle by decreasing the pre-ovulatory LH peak and E2 and postovulatory E2 levels that affect the endometrial growth, and consequently reduce the chances to conceive.

Efficiency of CIDR-Based Protocols Including GnRH Instead of eCG for Estrus Synchronization in Sheep.

Simple SummaryThis study examines the preovulatory and ovulatory events (in terms of the timing of onset of estrus behavior, preovulatory LH surge, and ovulation) and the yields obtained (in terms of ovulation rate, progesterone secretion, and fertility) after insertion of controlled internal drug release (CIDR) devices for 5 days and treatment with equine chorionic gonadotrophin (eCG) or gonadotrophin-releasing hormone (GnRH).The present study examined, for meat sheep (Segureña breed; 2–5-years old, mean body score of 3.5 ± 0.5), the timings of onset of estrus behavior, preovulatory luteinizing hormone (LH) surge and ovulation, and the ovulation rate and fertility obtained after insertion of controlled internal drug release (CIDR) devices for 5 days plus treatment with equine chorionic gonadotrophin (eCG; single dose at CIDR removal, n = 19 ewes) or gonadotrophin-releasing hormone (GnRH, either in a single dose at 56 h after CIDR removal, group CIDR-GnRH, n = 19 ewes; or in one dose at CIDR insertion and another dose 56 h after CIDR removal, group GnRH-CIDR-GnRH, n = 19 ewes). In all the ewes, the appearance of estrus behavior ranged between 84% and 90% and all females showing estrus signs had subsequent preovulatory LH peaks and ovulations. Onset of these events was earlier in the CIDR-eCG group than in the CIDR-GnRH and GnRH-CIDR-GnRH groups (p < 0.05). These differences were mainly determined by the onset of estrus behavior, since timing and intervals of LH peak and ovulation were similar among treatments. In fact, the range of ovulations was narrower in the GnRH-CIDR-GnRH group, which suggests better synchronization of follicular growth (p < 0.05). In conclusion, protocols with two doses of GnRH offer similar yields to eCG protocols.

Identifying ovarian tissue in the bitch using anti-Müllerian hormone (AMH) or luteinizing hormone (LH)

Reliable methods for determining whether or not a bitch has ovarian tissue present are needed for cases with unknown neutering status. Vaginal cytology consistent with heat is indicative of functional ovarian tissue. Other methods are required when the bitch is not presented in suspected heat. Progesterone can be analyzed during 2 months after suspected heat. During other stages, assays for the analyses of anti-Müllerian hormone (AMH) and luteinizing hormone (LH) have been used. The AMH assay is expected to give detectable concentrations (positive) in bitches with ovarian tissue, and the LH assay should give negative results in intact bitches, except during the pre-ovulatory LH peak. The aim of the present study was to study the diagnostic efficiency for detecting ovarian tissue in bitches using an AMH assay developed for human samples, and a semi-quantitative rapid immune migration (RIM™) LH assay developed for use in dogs. An AMH concentration of ≥0.1 μg/L, and an LH concentration of ≤1 μg/L, was set as the cut-off for presence of ovarian tissue. Client or staff owned bitches were included (N = 125). There were 73 intact bitches that were classified as being in heat (N = 25); in luteal phase (N = 12); or in anestrus (N = 36), and 52 spayed bitches that showed no clinical signs of estrogen influence. In total 64 of the 73 intact bitches (88%) were correctly identified using AMH, and 70/73 (96%) intact bitches were correctly identified using the LH assay. Excluding bitches in heat, the corresponding figures were 42/48 (88%) for AMH and 48/48 (100%) for LH. Of the 52 spayed bitches, 51 (98%) were correctly identified using the AMH assay and 49 (94%) were correctly identified using the LH assay. In this population, the predictive value of a positive AMH for intact bitches was 98%, and of a negative AMH for spayed bitches was 85%. Excluding bitches in heat, the predictive value of a negative LH test for intact bitches was 94%, and the predictive value of a positive LH test for identifying spayed bitches was 100%. It was concluded that analyses of AMH and LH are useful for detecting ovarian tissue in bitches, but that low concentrations of AMH may be obtained in intact bitches, classifying them as spayed. For LH, bitches in suspected estrus should not be tested to avoid the pre-ovulatory LH-surge, that otherwise may cause intact bitches being incorrectly identified as spayed.

Progesterone (P4), luteinizing hormone (LH) levels and ovarian activity in postpartum Santa Inês ewes subject to a male effect

Abstract. This study aimed to establish P4 and luteinizing hormone (LH) levels and ovarian activity as approaches to monitor the cyclicity of ewes under postpartum anestrus after the male effect approach. Santa Inês females (n = 66) were evenly distributed into experimental groups where they were brought into contact with an intact male during the postpartum period of 35 to 40 days (T1) and 55 and 60 days postpartum (T2). Ewes were isolated from males for 30 days before the onset of the experiment. Estrus events were detected in 93.30 % (T1) and 100 % (T2) of females. Mean P4 concentrations (η g mL−1) before and after mating were 0.53 ± 0.17 and 4.55 ± 0.24 (T1) and 0.73 ± 0.06 and 4.90 ± 0.11 (T2), respectively, and concentrations were found to be lower (P &lt; 0.05) before contact between genders. Preovulatory peaks of LH (η g mL−1) were evaluated at 42 (T2) and at 80 h (T1) after exposure to males, with mean ovulatory follicles of 7.90 ± 0.31 (T1) and 8.50 ± 0.30 mm (T2) and a mean number of ovulations of 1.50 ± 0.54 (T1) and 1.60 ± 0.51 (T2). Pregnancy rates were 85.70 % (T1) and 93.3 % (T2), with no difference (P &gt; 0.05) between groups. Results showed that the male effect was effective for inducing and concentrating the occurrence of estrus in postpartum ewes that had lambed within 35 to 60 days previously. Moreover, preovulatory LH peaks occurred within 80 h after physical contact between genders, which led to follicle luteinization and increased P4 concentration, without compromising pregnancy rates. The male effect can be used with postpartum ewes that had lambed within 35 to 40 days previously in order to decrease time between deliveries.

Pırlak koyunlarda Kisspeptinin LH profili ve reprodüktif parametrelere etkileri

In this study, it was investigated, the effects of application of Kisspeptin-10 (Kp-10) on the luteinizing hormone (LH) profiles and reproductive parameters. Total 60 Pirlak sheep were allocated into 3 equal (n=20) groups in breeding seasons. Estrous cycles were synchronized with double PGF2α method. Following a second cloprostenol injection, the Group 1 was treated with human kisspeptin-10 (1µg/kg) once at 40th h but the Group 2 was treated with Kp-10 (1µg/kg) twice at 40th and 50th h. The Group 3 was not treated with Kp-10 but treated with serum physiologic. All group of ewes were mated between 42nd and 43rd hours by hand mating system. Onset of LH surge and peak time of LH occured similar time in all groups. Group 2 plasma levels of LH at 50.5 h following last cloprostenol was found higher than Group 1 and Group 3 (p=0.005). Preovulatory LH peak concentration of Group 2 was found higher than Group 1 and Group 3 (p=0.030). Duration of LH surge was 18,63 ± 7,21, 18,03 ± 5,00 and 12,55 ± 6,93 h respectively in Group 1, 2 and 3 (p=0.009). Group 1and Group 2 of the area under the curve for LH (LH AUC) at 55 h were higher than Group 3 (p=0.042). Progesterone (P4), estradiol (E2) profiles and oestrus, conception, fecundity and prolificacy rates were found to be similar (p> 0.05) between the all groups. As a result, it was found that Kp-10 can be affect LH profiles but had no significant change on reproductive parameters

Vaginal impedometry for detection of optimal breeding time in bitches.

To compare the efficacy of canine vaginal impedometry in identifying the preovulatory luteinizing hormone (LH) peak to that of currently used methods (serum progesterone concentration measurement, vaginal cytologic evaluation, and vaginoscopy). Prospective study. 12 sexually intact female dogs. 12 mature postpubertal Beagle (n = 3), Beagle-cross (2), and hound-cross (7) bitches ranging from 7.5 to 27.5 kg (16.5 to 60.6 lb) were enrolled in the study. After the onset of spontaneous proestrus, determined on the basis of appearance of serosanguineous vaginal discharge, serum progesterone assays, vaginoscopy, vaginal cytologic evaluation, and vaginal impedometry were performed daily until approximately 4 days after peak LH concentration (day 0) as measured by radioimmunoassay. Vaginal impedometry was compared against serum progesterone concentration measurement, vaginal cytologic evaluation, and vaginoscopy as a method for accurately identifying the LH peak and therefore the optimal breeding time. Ten of 12 bitches were bred with subsequent assessment of embryos. Vaginal impedometry accurately predicted the preovulatory LH peak in 5 of 11 bitches. One bitch was removed from the study because data were not collected. Of the remaining 11 bitches, 6 had their LH peak on the day serum progesterone concentration first exceeded 2 ng/mL. Crenulation scores reached 1 (mean, 1.3; 95% confidence interval, 0.8 to 1.7) on day 0 as expected; however, these scores were not significantly different from those on days -1 or 1. Vaginal epithelial cell populations did not change noticeably on day 0. Nine of the 10 bitches that were bred produced viable embryos. Results suggested that daily use of vaginal impedometry in bitches was unreliable as a method for monitoring periovulatory events. All techniques evaluated (ie vaginal impedometry, serum progesterone concentration assays, vaginoscopy and vaginal cytologic evaluation) frequently produced inaccurate results when used individually. Multiple methods should be used to identify optimal breeding time in dogs.

Preliminary observations on the concentrations of serum luteinizing hormone and follicle-stimulating hormone during gestation in bactrian camels (Camelus bactrianus).

The concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the serum of the Bactrian camel (Camelus bactrianus) throughout pregnancy were analysed by radioimmunoassay. The samples were withdrawn at intervals of half a month. The serum LH concentrations varied significantly between 2.2+/-0.9 and 20.3+/-18.8 ng/ml during the pregnancy, with the highest value on the day of artificial insemination, which indicated that a preovulatory LH peak appeared. Thereafter, the LH concentration tended to fall, reaching a fairly constant low level by the eighth month of pregnancy. The serum FSH concentrations varied between 7.0+/-0.2 and 28.9+/-0.4 ng/ml during gestation, with the peak value being reached at 4.5 months, followed by a marked drop to 7.0+/-0.2 ng/ml at 7.5 months.

Apparition des chaleurs et de la décharge préovulatoire de LH chez la brebis de race Djallonké après synchronisation des chaleurs avec ou sans PMSG

En vue d'étudier l'influence de la PMSG sur l'apparition des chaleurs et le pic préovulatoire de LH chez les brebis Djallonké, les oestrus de 80 brebis cyclées ont été synchronisés à l'aide d'éponges vaginales d'acétate de fluorogestone en saison sèche et chaude.

Characteristics of urinary luteinizing hormone (LH) during the induction of LH surges of different magnitude in blood.

Urinary luteinizing hormone (LH) testing has been proposed as a reliable method for the prediction of ovulation but its accuracy has been challenged by some studies. To check how accurately the oscillations of urinary LH reflected the plasma changes, surges of LH of different magnitude and duration were artificially induced in plasma and the hormone was measured simultaneously in urine. Post-menopausal women (n = 16) were stimulated during 1 week with a combination of transdermal oestradiol (400 micrograms) and i.m. progesterone (25 mg on day 4, 50 mg on day 5) to obtain an LH discharge comparable with the pre-ovulatory LH peak. A short and moderate peak of LH was induced by the i.v. injection of 100 micrograms gonadotrophin-releasing hormone (GnRH) in six premenopausal women, whereas an LH discharge of higher amplitude and longer duration was induced by a single dose of 0.3 mg s.c. buserelin. The total urine production of the day was fractionated into 8 h periods. LH was measured by a commercial radioimmunoassay. Unambiguous peaks of LH were detected in the urine of all the women stimulated with either oestradiol plus progesterone or buserelin, but in only three out of the six women receiving GnRH. The urine LH reproduced the plasma changes of the hormone with short delay since the peaks were mostly detected in the same time fraction in which the serum discharge occurred.

The influence of the preovulatory LH peak on protein synthesis and phosphorylation in bovine oocytes from follicles of different size and quality

Whether the luteinizing hormone (LH) peak induces oocyte maturation in other than preovulatory follicles was examined by analysing protein synthesis and phosphorylation patterns of bovine oocytes from non-atretic and atretic follicles of various sizes, present in the ovaries of oestrous animals treated for superovulation. The oocytes were collected at consecutive times after the preovulatory LH peak, radiolabelled for 3 h and individually processed for SDS-PAGE. Furthermore, the nuclear status of the oocytes, the expansion of their cumulus investment, the luteinization of their granulosa cells and steroid levels in the corresponding follicular fluids, were scored and related to the protein synthesis and phosphorylation patterns obtained. Oocytes from non-atretic follicles of 3–8 mm, collected between 3 and 20 h after the LH peak, exhibited consistent protein synthesis and phosphorylation patterns similar to those of oocytes from preovulatory follicles collected 3–8 h after the LH peak in the germinal vesicle (GV) stage. The majority of oocytes from small follicles were in the GV stage and surrounded by a compact cumulus investment throughout the collection period. In these follicles, no luteinization of the membrana granulosa was observed, while the oestradiol-17β level declined during the collection period. The results indicate that the LH peak affects the theca interna of small follicles, but does not induce further follicular differentiation or oocyte maturation. The protein synthesis and phosphorylation patterns of oocytes from atretic follicles larger than 10 mm, as well as their nuclear status and cumulus expansion, were similar to those of preovulatory follicles during the collection period. The timing of changes in the steroid levels during this period was similar in non-atretic and atretic follicles. The results show that oocyte maturation is induced in all follicles larger than 10 mm.

Concentrations of luteinizing hormone and oestradiol in plasma and response to injection of gonadotrophin-releasing hormone analogue at selected stages of anoestrus in domestic bitches.

Concentration of plasma luteinizing hormone (LH) and oestradiol concentrations and responses to a standard challenge with a gonadotrophin-releasing hormone (GnRH) analogue were measured at certain stages of anoestrus during consecutive cycles in five beagle bitches. Blood samples were collected every 20 min for 6h followed immediately by injection of GnRH analogue (0.16 micrograms i.v.) and collection of further samples after 10, 20, 40 and 60 min. Five, 10, 17 and three such sampling sequences were obtained during the luteal phase, transition to anoestrus, anoestrus and pro-oestrus respectively (i.e. 154-71, 114-44, 85-11 and 7-1 days before the preovulatory LH peak, respectively). Pulsatile LH secretion occurred spontaneously at all stages of the luteal phase and anoestrus and there was no effect of cycle stage on mean LH concentration or variability. In contrast, oestradiol could not be detected in most samples from early and mid-anoestrus until approximately one month before the preovulatory LH peak, after which average oestradiol concentration and between sample variability appeared to increase. Mean (+/- SEM) oestradiol concentration for all samples collected from 100-75, 74-50, 49-25, 24-10 and 9-1 days before LH peak was 1.4 +/- 0.1, 1.3 +/- 0.1, 2.4 +/- 0.3, 11.0 +/- 1.4 and 36.0 +/- 3.2 pg ml-1, respectively. Plasma LH concentration increased in all bitches after GnRH analogue injection (2.7 +/- 0.7 ng ml-1 at t = 0, 12.5 +/- 1.0 ng ml-1 at t = 10 min, mean +/- SEM, n = 35) regardless of cycle stage.(ABSTRACT TRUNCATED AT 250 WORDS)

Structural aspects of bovine oocyte maturation in vitro.

Bovine cumulus-oocyte complexes (COCs) were collected from 4-8 mm follicles and graded into four categories on their morphological characteristics. These four categories were matured in vitro and processed for transmission electron microscopy at 24 h after the onset of culture. The morphology of the four groups of oocytes was analysed and compared with that of oocytes that had matured in vivo and were collected 20-23 h after the preovulatory luteinizing hormone peak. After in vivo maturation, oocytes formed a homogeneous group with respect to their morphological characteristics. After in vitro maturation, the oocytes formed a heterogeneous group with respect to their morphology between as well as within the four categories of oocytes. Oocytes from the first three categories showed the same morphology after in vitro maturation. The fourth category showed some specific characteristics: 1) vacuolization, 2) flattening of cumulus cells, and 3) almost complete lack of cortical granules in some category 4 oocytes. These characteristics are interpreted as signs of degeneration. Besides these aspects of degeneration, other deviations from normal development were seen: 1) retraction of cumulus cell process endings from the oocyte without the breaking down of these processes, 2) retardation of some aspects of the cytoplasmic maturation, and 3) incomplete cumulus expansion. It is concluded that oocytes capable of development in vitro show a large morphological variability before the onset of culture. In vitro maturation systems can support normal development, but many oocytes show signs of degeneration and deviant development after in vitro maturation.

Monitoring the ovarian cycles of Pan troglodytes and P. paniscus: A comparative approach.

Females of both species of chimpanzee, Pan troglodytes and P. paniscus, exhibit conspicuous anogenital sex swellings that are useful external markers for assessing ovarian cyclicity. A new, quantitative method for describing these swelling cycles was refined during laboratory studies of four P. paniscus and nine P. troglodytes and was used to analyze variability in swelling patterns. Clear-cut anatomical changes of the perineum were found to have both interindividual and interspecific reliability. The swollen phase of the cycle was defined as the period when the medial surfaces of the labia minora are pressed against each other so the aperture leading to the vagina appears as a slit (labial occlusion). When defined with this precision, comparisons within and between the species revealed two types of cycle for both species; swollen phases of P. paniscus were about 24 or 39 days in duration, on average, whereas those of P. troglodytes were about 14 or 18 days. Urine samples from the P. troglodytes were collected and analyzed for luteinizing hormone (LH) (34 cycles), estrone glucuronide (E1G), and pregnanediol-3-glucuronide (PdG) (18 cycles). When the two types of cycle were separated in analysis, it was found that the day when labial occlusion occurred served as a predictor of the preovulatory LH peak in the cycles with a long swollen phase. Levels of E1G correlated closely with swelling scores in multiparous females regardless of phase lengths, suggesting that the new swelling scores are a reliable indicator of E1G excretion in multipara. Cycles with long swollen phases had relatively high levels of PdG during the luteal phase, whereas cycles with short swollen phases had relatively low levels of PdG and a shorter luteal phase. The marker of labial occlusion and the duration of the preswollen phase defined by the marker appear to be potentially useful in studies of reproduction in Pan, for monitoring female fertility, and in artificial insemination procedures. If it is confirmed that swelling pattern predicts progesterone levels during the luteal phase, it would make interventions possible in the case of low levels so that a potential pregnancy could be maintained to term.

Periovulatory Endocrinology and Oocyte Maturation in Unmated Mature Blue Fox Vixens (Alopex lagopus)

Nine of 10 mature blue fox vixens (Alopex lagopus) in spontaneous oestrus ovulated approximately 2 days after the preovulatory increase in luteinizing hormone (LH). Plasma concentrations of follicle-stimulating hormone and progesterone increased simultaneously with the LH peak, whereas oestradiol-17 beta peaked 1 day previously. In the tenth vixen, an LH peak was not observed, and neither visible follicles nor corpora lutea were found in the ovaries 6 days after peak vaginal electrical resistance. Eggs were ovulated as primary oocytes, but oocyte maturation was initiated within the day of ovulation (2 days after the LH peak). Within the next 2 days (3-4 days after the LH peak) the first polar body was extruded, and the cumulus mass was completely dissociated from the zona pellucida. The interval between the preovulatory LH peak and initiation of the final oocyte maturation is thus considerably longer in the blue fox than for example in the cow (48-72 h compared with 9-12 h). This suggests that the relationship between these two events is somewhat different in the blue fox.

Reproductive hormone concentrations during estrus, pregnancy, and pseudopregnancy in the Labrador bitch

Serum luteinizing hormone (LH), estrone, estradiol-17β, and progesterone were measured during the estrous cycle, pregnancy and parturition in seven adult pregnant Labrador bitches and during the estrous cycle and one gestation length equivalent in six adult pseudopregnant bitches. Although the duration of proestrus was similar in both groups, the duration of estrus was longer in the bitches that subsequently became pregnant. Mean serum LH concentrations were similar in both groups during most of the study. However, during Weeks 6 to 9 after the preovulatory LH peak, serum LH concentration was higher in both pseudopregnant and pregnant groups of animals and declined to basal levels thereafter. Mean serum estrone concentrations in the pregnant animals were higher than those of pseudopregnant animals and remained elevated throughout gestation, followed by a decline at whelping. Serum estradiol-17β levels were higher during the 4 wkimmediately following ovulation in the pseudopregnant group compared with those observed in pregnant animals. Serum progesterone concentrations generally remained higher during pseudopregnancy compared with those of the pregnant animals during gestation. In conclusion, a major difference between pregnant and pseudopregnant bitches is a pregnancy-specific elevation in estrone levels. The placenta may be a likely source of estrone during pregnancy.

Sequential endocrine changes and behaviour during oestrus and metoestrus in repeat breeder and virgin heifers

The aim of the experiment was to study the oestrous behaviour and the peripheral blood plasma profiles of luteinizing hormone (LH), progesterone and the prostaglandin metabolite, 15-keto-13,14-dihydro-PGF 2α, during oestrus and metoestrus in repeat breeder (RBH) and virgin heifers (VH). Ten animals of each category were utilized. The RBH had a history of at least three inseminations without conception, and the VH were sexually mature animals not previously inseminated or mated. Oestrous symptoms were recorded and blood collected from the onset of prooestrus to 7 days after oestrus. The animals were inseminated during oestrus and their embryos were collected by a nonsurgical technique 7 days after insemination. The morphology of the embryos was evaluated. The duration of oestrus was longer ( P < 0.05) in the RBH (31.5 ± 3.6 h) than in the VH (23.8 ± 2.0 h). No differences in duration of prooestrus or in the interval from the end of oestrus to postoestrous bleeding were found between the heifer categories. The interval from the onset of oestrus to the preovulatory LH peak was longer ( P < 0.05) in the RBH (12.2 ± 2.8 h) than in the VH (4.8 ± 1.5 h). There was a lower LH release in the RBH than in the VH, measured as the magnitude of the preovulatory LH peak ( P < 0.05; 28.0 ± 4.0 vs. 40.7 ± 3.6 μg/l) or as the area under the curve of the LH peak ( P < 0.01; 1141 ± 164 vs. 1765 ± 144 mm 2). The progesterone levels were higher ( P < 0.05) in the RBH than in the VH during the interval 5–48 h and lower ( P < 0.05) during the interval 121–168 h after the LH peak. Peaks of the prostaglandin metabolite were seen during oestrus in both heifer groups. There were more prostaglandin metabolite peaks in the RBH than in the VH during the interval 13–24 h after the LH peak. Fewer normal embryos ( P < 0.05) and more degenerated embryos ( P < 0.01) were found in the RBH than in the VH group 7 days after insemination. No apparent relation was found between the morphology of the embryos and the hormonal changes. The result of the study indicates a hormonal imbalance in the RBH. The hormonal asynchronism starts before or early in oestrus, which presumably leads to a sequence of improper hormonal changes responsible for the elevated embryonic loss in repeat breeder animals.

Serum androstenedione and testosterone concentrations during pregnancy and nonpregnant cycles in dogs.

Concentrations of testosterone and of androstenedione were determined by radioimmunoassay in serum samples collected every 2-5 days throughout the periovulatory and luteal phases of the ovarian cycles of pregnant and nonpregnant beagle bitches. Testosterone levels were consistently lower than those of androstenedione, reached peaks of 29 +/- 4 ng/dl near the time of the preovulatory luteinizing hormone peak, and were reduced to near the limits of detection (less than or equal to 5-10 ng/dl) throughout the luteal phase. Androstenedione levels reached preovulatory peaks of 73 +/- 13 ng/dl, were 54 +/- 7 ng/ml during early estrus, increased (P less than 0.05) to early luteal phase peaks of 76 +/- 8 ng/dl between Days 6 and 18, and then declined to 41 +/- 5 ng/dl by Day 35-40 in both pregnant (n = 8) and nonpregnant (n = 4) bitches. Subsequent protracted increases in androstenedione occurred in 4 of 8 pregnancies but in none of the nonpregnant bitches. From Days 42 to 64 the differences in mean levels between pregnant (45 +/- 2 ng/ml) and nonpregnant (32 +/- 3 ng/ml) bitches was not significant (P greater than 0.05). At parturition androstenedione levels fell (P less than 0.05) abruptly from 39 +/- 7 to 13 +/- 3 ng/dl. These results suggest that, in the bitch, androstenedione is the major circulating androgen during the follicular and luteal phases and that patterns of androstenedione levels during the luteal phase parallel those reported for progesterone in pregnant and nonpregnant bitches, including maintenance of elevated levels throughout gestation and an abrupt decline at parturition.

Evidence for a positive feedback interaction between progesterone and luteinizing hormone in the induction of ovulation in the hen, Gallus domesticus

Two experiments were conducted to test the hypothesis that progesterone (P 4) acts to induce a preovulatory rise of luteinizing hormone (LH) by initiating a true positive feedback interaction between P 4 and LH. In each experiment, ten hens were stereotaxically implanted with a third ventricle cannula. Aminoglutethimide phosphate (AGP), an inhibitor of steroidogenesis, was administered (200 mg iv) to hens at 10 and 6 hr (Experiment 1) and 10 and 7 hr (Experiment 2) before an expected C 1 ovulation. A 20-μg injection of P 4 ( n = 5) or the vehicle ( n = 5) was made intraventricularly at 6 hr (Experiment 1) or 7 hr (Experiment 2) before the expected ovulation. Blood samples were taken via branchial vein cannula at regular intervals after the injection. In Experiment 1, four of five P 4-treated hens ovulated, and no atretic follicles were found in any of the five P 4-treated hens, including the one which did not ovulate. Ovulations were always accompanied by preovulatory LH peaks. By comparison, none of the vehicle-injected animals ovulated and in four of five hens the largest follicle was determined to be atretic. No ovulations occurred in Experiment 2 for either the P 4- or vehicle-injected hens. Atresia of the largest follicle occurred in all five hens in the P 4-treated group and four of five hens of the vehicle-treated group. The difference in results between Experiment 1 and Experiment 2 can be explained assuming that the steroidogenesis-inhibiting action of the initial AGP injection in Experiment 1 (at 10 hr before ovulation) had diminished prior to the second AGP treatment (at 6 h before ovulation). In both Experiments 1 and 2, intraventricular P 4 injection caused a significant ( P < 0.001 for Experiment 1; P < 0.03 for Experiment 2) rise in plasma P 4 within 10 min after injection due to leakage of P 4 from the third ventricle into the systemic circulation. Nevertheless, in the absence of any steroid feedback from the ovary (Experiment 2), the small rise in LH induced by the P 4 injection was not potentiated, and no preovulatory surge of LH occurred. These results support the hypothesis that a positive feedback interaction between P 4 and LH, in contrast to a stimulatory effect of P 4, is necessary for the preovulatory LH surge and ovulation.

A note on the relationship between undernutrition and luteinizing hormone release in the ewe

ABSTRACTThe effects of a moderate level of undernutrition on the release of luteinizing hormone (LH) at oestrus and after luteinizing hormone releasing hormone (LHRH) treatment was investigated. Plasma levels of glucose, non-esterified fatty acids (NEFA), cortisol and prolactin were also investigated.During the early breeding season 10 mature ewes were placed on either a maintenance (M) or a restricted (R) diet. After 50 days of dietary treatment their oestrous cycles were synchronized and blood samples were taken over the oestrous period. Eight days later LHRH was administered and blood samples were taken for the following 6 h.After 50 days of treatment mean body- weights were 66 (s.e. 4) and 53 (s.e. 3) kg, and mean body condition scores were 3·5 and 2·0 for the M and R groups respectively. The pre-ovulatory and LHRHinduced LH peaks were similar in both groups as were the prolactin profiles. However, plasma NEFA levels were elevated and glucose and cortisol levels were reduced in the restricted group.It is concluded that the reduction in energy intake achieved in this experiment, although sufficient to cause significant metabolic changes had no effect on the release of LH either at oestrus or after LHRH treatment.