Altered ovarian reserve in Ewe lambs exposed to a glyphosate-based herbicide

Glyphosate-based herbicides (GBHs) are considered endocrine disruptors that affect the female reproductive tract of rats and ewe lambs. The present study aimed to investigate the impact of neonatal exposure to a low dose of a GBH on the ovarian follicular reserve of ewe lambs and the response to a gonadotropic stimulus with porcine FSH (pFSH). To this end, ewe lambs were orally exposed to an environmentally relevant GBH dose (1 mg/kg/day) or vehicle (Control) from postnatal day (PND) 1 to PND14, and then some received pFSH (50 mg/day) between PND41 and 43. The ovaries were dissected, and follicular types and gene expression were assessed via RT-PCR. The treatments did not affect the body weight of animals, but pFSH increased ovarian weight, not observed in GBH-exposed lambs. GBH-exposed lambs showed decreased Estrogen receptor-alpha (56%), Progesterone receptor (75%), Activin receptor II (ACVRII) (85%), and Bone morphogenetic protein 15 (BMP15) (88%) mRNA levels. Control lambs treated with pFSH exhibited downregulation of Follistatin (81%), ACVRII (77%), BMP15 (93%), and FSH receptor (FSHr) (72%). GBH-exposed lambs treated with pFSH displayed reduced ACVRII (68%), BMP15 (81%), and FSHr (50%). GBH-exposed lambs also exhibited decreased Anti-Müllerian hormone expression in primordial and antral follicles (27%) and (54%) respectively) and reduced Bone morphogenetic protein 4 (31%) expression in primordial follicles. Results suggest that GBH disrupts key follicular development molecules and interferes with pFSH action in ovarian receptors, decreasing the ovarian reserve. Future studies should explore whether this decreased ovarian reserve impairs adult ovarian function and its response to superovulation stimuli.

Reproductive Activity of Socorro Island Merino Ewes and Their Crosses with Pelibuey under Heat Stress Conditions

An experiment was carried out to evaluate the effect of spring and autumn seasons on the reproductive activity of Merino Socorro Island ewes and their crosses with Pelibuey under heat stress (HS) conditions in the tropics. All ewes (n = 80) were randomly assigned to one of two breeds during the first and second periods, respectively: (1) Twenty Socorro Island Merino ewes (SIM) and (2) 20 Pelibuey Crossbred ewes (PBC). Animals were fed the same diet and given water ad libitum. All statistical analyses were performed using SAS statistical software 9.12 procedures. In both seasons, a mean of more than 80 U of maximum THI was obtained, while in spring and autumn, the minimum THI exceeded 30 and 40 U, respectively. All animals were in oestrus and ovulated in both seasons. The frequency of animals in spring during the first 48 h of oestrus expression was greater (p < 0.05) than 48-55 h but similar (p > 0.05) than 55-65 h; in autumn during the first 48 h and 48-55 h were similar (p > 0.05), but different (p < 0.05) than 55-65 h. The duration of oestrus expression was longer in the spring than in the autumn (p < 0.05). The frequency of animals was higher (p < 0.05) in SIM than in PBC ewes during the first oestrus cycle (1-17 d) and was also higher (p < 0.05) in PBC than in SIM ewes during the second oestrus cycle (18-35 d). The SIM ewes produced more (p < 0.05) progesterone (P4) than the PBC ewes. During the sampling days of the oestrus cycle, more P4 was created in autumn than in spring (p < 0.05). Both breeds showed severe HS. In the future, ewes treated under assisted reproductive programs in the tropics may improve reproductive efficiency.

Nuclear and membrane progesterone receptors expression in placenta from early to late pregnancy in sheep: Effects of restricted nutrition and realimentation

Nutrient restriction and/or realimentation may affect several placental functions, such as expression of selected regulatory factors, blood flow and other processes in sheep and other species. To determine the effects of the plane of nutrition, nulliparous white face ewes (6-8 months) carrying singletons on day 50 of gestation were randomly assigned to two dietary treatments receiving 100% of National Research Council recommendations (control; C) or 60% of C (restricted; R). Two groups remained on C or R diets from day 50 until day 130. From day 90-130 another group of C fed ewes was switched to the R diet, and another group of R fed ewes was switched to the C diet. This resulted in 7 groups (n = 5-6 ewes/group): C (day 50, 90 and 130), R (day 90 and 130), CR (day 130) and RC (day 130). At these time points, placental tissues were collected for the evaluation of progesterone receptor (PGR) protein expression (whole tissue), and mRNA expression in maternal (caruncular, CAR) and fetal (cotyledon, COT) (separated tissues). Data were statistically analyzed using analysis of variance (SAS 9.4). Protein for PGRAB and PGRB isoforms was detected using immunohistochemistry in all placental tissues, but the pattern of expression differed depending on pregnancy stage and placental compartment (e.g., CAR vs COT). PGRAB protein expression, quantified using image analysis, was greater (P < 0.04) on day 50 than 90 or 130, and was not affected by plane of nutrition. In CAR and COT, PGRAB mRNA expression was greater (P < 0.05) on day 50 than 90 or 130. PGRB mRNA expression was greater (P < 0.03) in CAR on day 50 than 90 and 130, and was greatest (P < 0.02) in COT on day 50, less on day 130, and least on day 90. For the membrane progesterone receptors, PAQR7 (membrane PGR alpha) mRNA expression was greater (P < 0.05) on days 50 and 90 than 130 in CAR, and greater (P < 0.01) on days 50 than 90 and 130 in COT; PAQR8 (membrane PGR beta) was similar throughout pregnancy in CAR and COT, and PAQR5 (membrane PGR gamma) was greatest (P < 0.0001) on day 130 in COT, but similar throughout pregnancy in CAR. Plane of nutrition affected (P < 0.05) mRNA expression for all genes in CAR and COT throughout pregnancy. These data indicate that expression of PGR in ovine placenta is dependent on stage of pregnancy and plane of nutrition in sheep. The mechanisms of how diet and stage of pregnancy influences placental PGR expression and function remains to be elucidated.

Expression of oestrogen receptor, androgen receptor and progesterone nuclear receptor in sheep uterus during the oestrous cycle

Oestrogen, androgen and progesterone are involved in the regulation of uterine physiological functions, with the participation of the following proteins: oestrogen receptor (ER), androgen receptor (AR) and progesterone nuclear receptor (PGR). In this study, we used immunohistochemistry to detect the localization of ERα, ERβ, AR and PGR in sheep uterus. Additionally, we used real-time polymerase chain reaction (RT-qPCR) and Western blot technique to analyse their expression profiles at different stages of sheep oestrous cycle in the endometrium and myometrium. Immunohistochemical analysis showed that ERα, ERβ, AR and PGR were present in sheep uterus in oestrus, mainly in the uterine luminal epithelium, stroma, gland and myometrium. Real-time polymerase chain reaction results showed that in the endometrium, ERα expression level was highest in oestrus. ERβ and PGR, instead, were highly expressed in pro-oestrus. In the myometrium, ERα was highly expressed in both oestrus and pro-oestrus, and ERβ was highly expressed in oestrus and dioestrus. Progesterone nuclear receptor expression was highest in oestrus, followed by metoestrus. In the endometrium, both receptors ERα and ERβ were abundant in pro-oestrus, while the maximum AR protein content was found in oestrus. At this stage of the oestrous cycle, PGR protein concentration in the myometrium was significantly lower than those observed in other stages. These results suggest that these receptors are important for sheep reproductive function, as their expression at mRNA and protein levels exhibits particular time- and tissue-specific profiles along the oestrous cycle.

Dietary restriction in sheep: Uterine functionality in ewes with different body reserves during early gestation

The aim of this study was to characterize insulin, leptin and IGF-1 profiles after undernutrition in pregnant ewes with different initial body condition (iBCS) and to investigate embryo quality, uterine gene expression and presence and location of proteins during early gestation (day 5). Thirty-six Rasa Aragonesa ewes were divided into 2 groups with different BCS: BCS> 2.75 (high, H, n = 19) and BCS <2.25 (low, L, n = 17) and they were randomly assigned to two nutritional treatments: 1.5 maintenance (M) (control, C) or 0.5 (M) (undernourishment, U) times the daily maintenance requirements establishing four groups: high-iBCS control (HC, n = 9), high-iBCS undernourished (HU, n = 10), low-iBCS control (LC, n = 9) and low-iBCS undernourished (LU, n = 8). High-iBCS ewes presented higher concentration of IGF-1, reflecting a better metabolic status in these animals. There was a greater proportion of high-iBCS ewes presenting more than one CL (P < 0.05), and associated greater P4 plasma concentration, number of recovered embryo and a tendency for higher embryo viability rate (P = 0.13). In uterus, undernourished ewes tended to present lower P4 (P = 0.09) and higher E2 concentration (P = 0.10). Inmunostaining of uterine progesterone and estrogen receptors (PR and ERα) was not affected by iBCS and nutritional treatment. Ewes with low-iBCS tended to have more INSR mRNA, and undernourished ewes tended to have more IGFBP2 mRNA expression (P < 0.08). An interesting finding was that the uterine response to undernutrition was dependent on iBCS: a higher expression of GHR (P < 0.05) and a tendency in IGFBP5 (P = 0.09) mRNA was found in undernourished than control ewes but only in the high-iBCS group. In summary, the present study demonstrates that the endocrine response and the uterine gene expression to undernutrition depend on the initial body energy reserves (iBCS) and appears to be associated with a differential embryo quality.

Neonatal exposure to a glyphosate-based herbicide alters the histofunctional differentiation of the ovaries and uterus in lambs

The aim of the present study was to compare the effect of oral and subcutaneous exposure to a glyphosate-based herbicide (GBH) on the female reproductive system, specifically in the ovaries and uterus of prepubertal lambs. To this end, ewe lambs were exposed to a s.c. (n: 5) or an oral (n: 5) environmentally relevant dose of GBH (2 mg/kg/day) or to vehicle (controls, n: 12), from postnatal day (PND) 1 to PND14. Serum glyphosate and aminomethylphosphonic acid (AMPA) concentrations were measured on PND15 and PND45. The ovaries and uterus were obtained and weighed on PND45. Ovarian follicular dynamics and uterine morphological features were determined by picrosirius-hematoxylin staining. The proliferation marker Ki67 was evaluated by immunohistochemistry in ovarian and uterine samples. Glyphosate but not AMPA was detected in serum of exposed lambs on PND15, whereas neither glyphosate nor AMPA were detected on PND45. Controls were negative for glyphosate and AMPA on PND15 and PND45. GBH exposure did not affect ovarian or uterine weight. However, on PND45, the ovary of GBH-exposed lambs showed altered follicular dynamics, increased proliferation of granulosa and theca cells, and decreased mRNA expression of FSHR and GDF9, whereas their uterus showed decreased cell proliferation but no alterations in the histomorphology or gene expression. In conclusion, GBH exposure altered the ovarian follicular dynamics and gene expression, and the proliferative activity of the ovaries and uterus of lambs. It is noteworthy that all the adverse effects found in the ovaries and uterus of both GBH-exposed groups were similar, independently of the administration route.

Placental development during early pregnancy in sheep: nuclear estrogen and progesterone receptor mRNA expression in the utero-placental compartments

Sex steroid hormones are major regulators of uterine and placental growth and functions, as well as many other biological processes. To examine the mRNA expression of nuclear estrogen (ESR1 and 2) and progesterone (PGRAB and B) receptors in different compartments of the uterus and placenta, tissues were collected in experiment 1 on days 16, 20, and 28 after natural mating (NAT) and on day 10 after estrus (nonpregnant controls [NP]); and in experiment 2 on day 22 of NAT, and pregnancies established after transfer of embryos generated through mating of FSH-treated ewes (NAT-ET), in vitro fertilization (IVF), or in vitro activation (parthenotes). In experiment 1, ESR1 expression in endometrial stroma (ES), endometrial glands (EGs), and myometrial blood vessels (MBVs), ESR2 in endometrial blood vessels (EBV), PGRAB in ES, and PGRB in ES, EG, and MBV was greater in pregnant than NP ewes depending on the day of pregnancy. The day of pregnancy affected the expression of ESR1 in MBV, ESR2 in EBV and MBV, and PGRAB in ES. In experiment 2, ESR1, PGRAB, and PGRB in EG, but not in other compartments, was greater in NAT-ET than NAT, and PGRB was greater for NAT-ET than IVF. These data demonstrate that ESR and PGR expression differ in pregnant versus NP ewes in selected compartments and was affected by pregnancy stage or embryo origin in selected utero-placental compartments. Thus, sex steroid hormone mRNA expression is differentially regulated in a spatiotemporal manner in the uterus and placenta and is affected by the application of assisted reproductive technology in sheep.

Placental development during early pregnancy in sheep: Progesterone and estrogen receptor protein expression

The aim of this study was to evaluate the pattern of protein expression of the steroid receptor isoforms of nuclear progesterone receptors (PGR) A and B, and estrogen receptors (ESR1 and 2) in utero-placental compartments during early pregnancy. Utero-placental tissues were collected from days 14-30 (n = 4 ewes/day), and uterine tissues were collected from non-pregnant ewes on day 10 after estrus (n = 4). Cross sections of formalin-fixed and paraffin embedded tissues were immunofluorescently stained to detect PGRAB, PGRB, ESR1 and ESR2, followed by image generation of entire cross-sections of uterine and utero-placental tissues, confocal imaging of individual uterine and utero-placental compartments, and image and statistical analyses. PGRAB, PGRB, ESR1 and ESR2 were detected in several compartments of uterine and utero-placental tissues. Quantitative image analysis of staining intensity demonstrated that compared to non-pregnant controls 1) expression of PGRAB and PGRB was less in luminal epithelium and endometrial glands from day 14-16 till 30; 2) PGRAB expression tended to be greater in endometrial and myometrial blood vessels on days 28 and/or 30; 3) PGRB expression in myometrum was lower on days 16 and 28; 4) ESR1 in endometrial stroma was lower in all days of pregnancy; 5) ESR2 expression was similar in all compartments and not affected by pregnancy stage; and 6) in FM, expression of steroid receptors was similar. Thus, we have demonstrated spatial and temporal expression of nuclear PGR and ESR isoforms in utero-placental compartments during early pregnancy.

Equine chorionic gonadotropin administration after insemination affects luteal function and pregnancy establishment in postpartum anestrous beef cows

Two experiments were conducted with the aim of determining the effect of equine chorionic gonadotropin (eCG) administration on day 14 after insemination on ovarian response and pregnancy establishment in postpartum anestrous beef cows. In both experiments, cows were subjected to a progesterone- and estradiol-based treatment for fixed-time artificial insemination (FTAI) and were randomly allocated into 4 groups to receive or not receive eCG (400 IU) at the time of device removal and/or at 14 d after FTAI. In experiment 1, from day 14 to 22, daily ultrasonographic determinations were performed to monitor ovarian dynamics, and blood was collected to determine hormone concentrations in 60 cows. In experiment 2, confirmation of pregnancy was performed at 30 and 60 d after FTAI in 1,060 anestrous cows assigned to the same experimental design. Cows that received eCG on day 14 after FTAI showed increases in corpus luteum area (P < 0.01), follicle diameter (P < 0.05), serum progesterone concentrations (P < 0.01), and estradiol-17β concentrations (P < 0.01), compared with cows that did not receive eCG on day 14. Pregnancy rate on day 30 was greater in those cows that received both eCG treatments (ie, at device removal and 14 d after insemination) than in those that did not receive eCG treatment (P < 0.05). In conclusion, eCG administered on day 14 after FTAI increases serum progesterone concentrations during the critical period of pregnancy in anestrous cows, and this second eCG treatment seems to have a positive effect on achieving pregnancy.

Effect of exogenous progesterone on embryo size and ewe uterine gene expression in an ovine 'dam size' model of maternal constraint

Progesterone (P4), acting via its receptor, regulates uterine function and histotroph production, which are crucial to embryo growth. This study aimed to examine exogenous P4 effects on embryo size and differential endometrial gene expression at Day 19 of gestation using a 'dam size' sheep model of maternal constraint. Purebred Suffolk (S, genotypically large) embryos were transferred into recipient groups of Cheviot (C, genotypically small) or Suffolk ewes that had, or had not, been pre-treated with P4 from Days 0 to 6 of pregnancy. At Day 19S embryos were collected from four experimental groups: P4 pretreated S ewes (SP4; n=5), untreated S ewes (SnP4; n=15), P4 pretreated C ewes (CP4; n=7) and untreated C ewes (CnP4; n=21). Day-19 embryos from CP4 ewes were larger (P<0.05) than those from CnP4 ewes and similar in size (P>0.05) to embryos from SnP4 and SP4 ewes. Expression of mucin 1 (MUC1) and prostaglandin-endoperoxide synthase 2 (PTGS2) was upregulated in uterine horns ipsilateral to the corpus luteum from CP4 ewes. Prostaglandin receptor (PGR), MUC1 and PTGS2 expression was upregulated, whilst cathepsin L (CTSL) and radical S-adenosyl methionine domain-containing 2 (RSAD2) expression was downregulated in the ipsilateral horn of SP4 ewes. This suggests that pretreating ewes with exogenous P4 may alleviate early pregnancy maternal constraint via mechanisms that alter uterine function. However, further research is required to investigate the timing of P4 administration and its impact on conception rates.

Expression of progesterone receptor protein in the ovine uterus during the estrous cycle: Effects of nutrition, arginine and FSH

To evaluate expression of progesterone receptor (PGR) AB in follicle stimulating hormone (FSH)-treated or non-treated sheep administered with arginine (Arg) or saline (Sal) fed a control (C), excess (O) or restricted (U) diet, uterine tissues were collected at the early, mid and/or late luteal phases. In exp. 1, ewes from each diet were randomly assigned to one of two treatments, Arg or Sal administration three times daily from day 0 of the first estrous cycle until uterine tissue collection. In exp. 2, ewes were injected twice daily with FSH on days 13-15 of the first estrous cycle. Uterine tissues were immunostained to detect PGR followed by image analysis. PGR were detected in luminal epithelium (LE), endometrial glands (EG), endometrial stroma (ES), myometrium (Myo), and endometrial and myometrial blood vessels. The percentage of PR-positive cells and/or intensity of staining were affected by phase of the estrous cycle, plane of nutrition, and/or FSH but not by Arg. In exp. 1, percentage of PGR-positive cells in LE and EG but not in ES and Myo was greater at the early and mid than late luteal phase, was not affected by plane of nutrition, and was similar in LE and EG. Intensity of staining was affected by phase of the estrous cycle and plane of nutrition in LE, EG and Myo, and was the greatest in LE, less in EG, and least in ES and Myo. In exp. 2, percentage of PGR-positive cells in LE, EG, ES and Myo was affected by phase of the estrous cycle, but not by plane of nutrition; was greater at the early than mid luteal phase; and was greatest in LE and EG, less in luminal (superficial) ES and Myo and least in deep ES. Intensity of staining was affected by phase of the estrous cycle and plane of nutrition in all compartments but ES, and was the greatest in LE and luminal EG, less in deep EG, and least in ES and Myo. Comparison of data for FSH (superovulated) and Sal-treated (non-superovulated) ewes demonstrated that FSH affected PR expression in all evaluated uterine compartments depending on plane of nutrition and phase of the estrous cycle. Thus, PGR are differentially distributed in uterine compartments, and PGR expression is affected by nutritional plane and FSH, but not Arg depending on phase of the estrous cycle. Such changes in dynamics of PGR expression indicate that diet plays a regulatory role and that FSH-treatment may alter uterine functions.

Placental development during early pregnancy in sheep: estrogen and progesterone receptor messenger RNA expression in pregnancies derived from in vivo-produced and in vitro-produced embryos

Sex steroids are important regulators of angiogenesis and growth in reproductive tissues, including the placenta. In experiment (exp.) 1, to examine the expression of a suite of sex steroid receptors throughout early pregnancy, maternal (caruncular [CAR]) and fetal (fetal membranes [FM]) placental tissues were collected on days 14 to 30 after mating and on day 10 after estrus (nonpregnant controls). In exp. 2, to examine the hypothesis that assisted reproductive technology would affect the expression of the same suite of sex steroid receptors, pregnancies were achieved through natural mating (NAT) or transfer of embryos from natural mating (NAT-ET), in vitro fertilization (IVF), or in vitro activation (IVA), and CAR and FM were collected on day 22. In exp. 1, for CAR messenger RNA (mRNA) expression of estrogen receptors (ESR) 1 and 2, nuclear (n) progesterone receptors (PGR) and membrane (m) PGRα, β, and γ were affected (P < 0.02) by pregnancy stage, as were ESR1, nPGR, and mPGRα, β, and γ for FM (P < 0.03). In exp. 2, for CAR, mRNA expression of ESR1 and nPGR was decreased (P < 0.001) in NAT-ET, IVF, and IVA groups compared with NAT. For FM, mRNA expression of ESR1 tended to be greater (P = 0.10) in the IVA group compared with NAT and NAT-ET, and GPER1 was greater (P < 0.05) in NAT-ET and IVF compared with NAT. These data establish the normal pattern of sex steroid receptor mRNA expression in maternal and fetal placenta during early pregnancy in sheep, and in addition, suggest that altered expression of placental sex steroid receptors may be an early event leading to poor placental vascularization and growth after assisted reproductive technology.

Endometrial population of oestrogen receptors alpha and beta and progesterone receptors A and B during the different phases of the follicular wave of llamas (Lama glama)

The aim of this study was to characterize the distribution of oestrogen receptor (ER)α and ERβ as well as both progesterone receptors isoforms progesterone receptor (PR) A and PRB in the luminal and glandular epithelia and stroma of the endometrium during the different phases of the follicular wave in llamas. Six llamas were examined by transrectal ultrasonography, and a transcervical biopsy was obtained when a follicle at the growing, plateau and regressing phase was recorded. Blood samples were collected at the time of biopsy for hormone determinations. An immunohistochemical technique was used to study receptor populations. Total positive area was evaluated in the different cell types by Image Analysis. Mean diameter measurements of the largest follicle were 6.9, 8.5 and 5.1 mm (p < 0.001) and mean plasma oestradiol-17β concentrations were 27.9 ± 3.26; 30.0 ± 2.79 and 24.0 ± 1.78 pmol/l (p = 0.32) during the growing, plateau and regressing phases, respectively. Immunostaining of ERα was higher in the luminal epithelium during the plateau and regressing phases (p < 0.05) than during the growing phase. More positive cells to ERβ were observed in the glandular epithelium of the growing and plateau phases (p < 0.05) than during the regressing phase. A higher percentage of cells positive to PRB was recorded in the luminal and glandular epithelia during the plateau phase (p < 0.05), while the PRA immunostaining was similar among phases. In brief, this study showed an increased population of ERα and PRB in the luminal epithelium, and only of PRB in the glandular epithelium at the time when an ovulatory follicle is present. The physiological importance of these changes in llamas remains to be elucidated.

Expression of genes for oestrogen and progesterone receptors in the cervix of anoestrous ewes treated with gonadotrophin releasing hormone with or without progesterone priming

The aim was to determine the oestrogens receptor alpha (ERα) mRNA and the binding capacity of oestrogens (ER) and progesterone receptor (PR) in the cervix of anoestrous ewes treated with gonadotrophin-releasing hormone (GnRH) with or without progesterone (P) priming, at the expected time of induced ovulation and early luteal phase. In Experiment 1, ewes were treated with P for 10 days (n=4), with nine micro-doses of GnRH followed by a GnRH bolus injection (n=4), or with P plus GnRH treatments (n=3), and tissues were harvested either without treatment (n=4), when P was removed, or 24h after the GnRH bolus injection. In Experiment 2, ewes were treated with the same GnRH or P plus GnRH treatments and tissues were harvested on Day 1 (n=12) or Day 5 (n=10) after the GnRH bolus injection. In the cranial cervix, the P treatment decreased and the GnRH treatment (after P treatment) increased the ERα mRNA, ER and PR concentrations (P<0.002). The ERα mRNA and ER concentrations were greater on Day 1, than on Day 5 in P plus GnRH treated ewes (P<0.0005). In the caudal cervix, lesser ERα mRNA, ER and PR concentrations than cranial cervix were found (P<0.0001). In conclusion, the ERα transcriptional activity and ER and PR binding capacity were strongly influenced by P and/or GnRH treatments in the cranial cervix, while the steroid receptors binding capacity remained unchanged in the caudal cervix of anoestrous ewes at the expected time of induced ovulation and early luteal phase.

Oestrogen and progesterone receptor binding capacity and oestrogen receptor alpha expression (ERalpha mRNA) along the cervix of cycling ewes

The aim of the present work was to study the oestrogen receptor (ER) and progesterone receptor (PR) binding capacity and the oestrogen receptor alpha (ERalpha) mRNA concentration in cranial and caudal cervix during the ovine oestrous cycle. Cervical samples of synchronised Corriedale ewes were obtained on Day 1 (n=7), 6 (n=6) or 13 (n=7) after oestrus detection (Day 0). The ER and PR binding capacity by ligand-binding assay and the ERalpha mRNA concentration by solution hybridisation in both cranial and caudal zones of the cervix were determined. The ER and PR binding capacity were higher (P<0.005) on Day 1 than on Days 6 and 13 in both cranial and caudal zones. The ERalpha mRNA concentrations were higher (P<0.0001) on Day 1 than on Days 6 and 13 only in the caudal zone. The PR binding capacity and ERalpha mRNA concentration were higher (P<0.005) in the caudal than in the cranial zone on Day 1. The ER and PR expression in the ovine cervix varied during the oestrous cycle in agreement with the known upregulation exerted by oestrogen and downregulation exerted by progesterone. Differences in ER and PR expression along the longitudinal axis of the ovine cervix were found, reflecting histological and functional differences between the cranial and caudal zones.

Review article: steroid hormones and uterine vascular adaptation to pregnancy

Pregnancy is a physiological state that involves a significant decrease in uterine vascular tone and an increase in uterine blood flow, which is mediated in part by steroid hormones, including estrogen, progesterone, and cortisol. Previous studies have demonstrated the involvement of these hormones in the regulation of uterine artery contractility through signaling pathways specific to the endothelium and the vascular smooth muscle. Alterations in endothelial nitric oxide synthase expression and activity, nitric oxide production, and expression of enzymes involved in PGI(2) production contribute to the uterine artery endothelium-specific responses. Steroid hormones also have an effect on calcium-activated potassium channel activity, PKC signaling pathway and myogenic tone, and alterations in pharmacomechanical coupling in the uterine artery smooth muscle. This review addresses current understanding of the molecular mechanisms by which steroid hormones including estrogen, progesterone, and cortisol modulate uterine artery contractility to alter uterine blood flow during pregnancy with an emphasis on the pregnant ewe model.

Influence of estrus of dairy goats on somatic cell count, milk traits, and sex steroid receptors in the mammary gland

Two experiments were conducted to study the effect of the stage of a spontaneous estrus cycle on milk yield and constituents [somatic cell count (SCC), fat, protein, caseins, lactose, and urea content] and on estrogen receptor-alpha (ERalpha ) and progesterone receptor (PR) immunostaining in the mammary gland. In experiment I, the major components of milk and SCC were monitored weekly in 80 lactating Saanen goats for 6 wk, whereas detection of estrus was daily. In experiment II, milk samples were collected daily for SCC determination during 1 spontaneous estrus (d 0) until the second spontaneous estrus in 14 Saanen goats. The day of the estrous cycle was confirmed by plasma progesterone and 17beta-estradiol levels. Immunoreactivity of ERalpha and PR was analyzed in mammary gland samples of 8 Saanen goats (d 0, n = 4; d 10, n = 4) and the number of positive nuclei and intensity of the staining were evaluated in 1,000 cells. In experiment I, milk casein and protein percentages were significantly affected by the stage of estrous cycle; during proestrus and estrus, these variables were higher (3.32 +/- 0.06 and 4.44 +/- 0.08) than during metestrus (3.03 +/- 0.07 and 4.07 +/- 0.10), but not higher than during diestrus (3.23 +/- 0.06 and 4.35 +/- 0.09, respectively). In experiment II, daily measurement of SCC revealed higher levels at estrus (7,195 +/- 672 x 10(3) cells/mL) and a decline toward the luteal phase (1,694 +/- 672 +/- 10(3) cells/mL). Estrogen receptor-alpha and PR immunostaining were exclusively detected on epithelial cells. The percentage of positive nuclei to ERalpha was higher on d 0 than on d 10 (75.4 +/- 8.8 vs. 68.3 +/- 8.8%), but no change was observed for PR (4.0 +/- 0.3 vs. 3.5 +/- 0.4%). The average immunostaining intensity for both receptors was greater on d 0 than on d 10 (ERalpha : 1.44 +/- 0.02 vs. 1.35 +/- 0.02; PR: 0.079 +/- 0.008 vs. 0.057 +/- 0.008). The high SCC at estrus in experiment II was associated with high plasma estradiol and low progesterone, suggesting that the increased SCC could be brought about by the estrogen-induced proliferation and exfoliation of epithelial cells. In addition, this action may be supported by the higher sensitivity to estrogens (ERalpha content) found at d 0.

Uterine estrogen receptor alpha and progesterone receptor during the follicular and luteal phase in llamas

Estrogen receptor-alpha (ERalpha) and progesterone receptor (PR) were characterized in different endometrial cell types as luminal and glandular epithelium and stroma during the follicular (FP) and the luteal phase (LP) in llamas. Animals were examined daily by transrectal ultrasonography for the determination of the presence of an ovulatory follicle and ovulation was immediately induced by a GnRH injection (Day 0). Endometrial samples were obtained by transcervical biopsies from the left uterine horn on Day 0 (FP) and 9 days after the GnRH injection (Day 9, LP). Blood samples were collected on these days for estradiol 17beta and progesterone determination by RIA. An immunohistochemical technique was used to visualize ERalpha and PR immunostaining which was then analyzed by two independent observers. Total positive area and average staining for ERalpha were affected by the phase of the ovarian activity: in the three cell types there was more positive area and intense staining during the FP than during the LP. Similar findings were observed for PR, more positive stained areas were found during the FP than during the LP in the epithelia. In addition, the three cell types had more intense staining during the FP than during the LP. An effect of the cell type for ERalpha and PR was observed; epithelia (luminal and glandular) had more positive stained areas and greater intensity than stromal cells. In conclusion, the results of the present study suggest that in llamas, like in other ruminants, estradiol has a stimulatory effect while progesterone downregulates the ERalpha and PR and that the receptor is cell type specific.

Effect of undernutrition on uterine progesterone and oestrogen receptors and on endocrine profiles during the ovine oestrous cycle

In the present study, it was investigated whether undernutrition affected the binding capacity, immunoreactivity and mRNA expression for uterine oestrogen and progesterone receptors (ER and PR, respectively) in sheep, as well as whether the responses were associated with changes in plasma concentrations of progesterone (P4), oestradiol (E2), glucose, fatty acids, insulin, leptin and insulin-like growth factor (IGF)-I during the oestrous cycle. Twenty ewes were fed either 1.5 (C) or 0.5 (L) times their maintenance requirements and were killed on Day 5 or 14 of the cycle (Day 0 = oestrus). Compared with Group C, Group L had higher concentrations of non-esterified fatty acids and lower concentrations of insulin, leptin and IGF-I. Group L also had higher plasma concentrations of P4 during the final days of the luteal phase. At oestrus in both treatment groups, there were peaks in the concentrations of glucose, insulin and IGF-I. For ER and PR, transcript expression, binding capacity and immunoreactivity were higher on Day 5 than on Day 14 of the cycle. The binding capacities for ER and PR were lower in Group L than in Group C on Day 5. Group C showed more immunoreactive staining for ER than did Group L in two of five cell types, whereas no effect of treatment was observed for PR immunoreactivity. There was more PR mRNA in the uterine horn contralateral to the corpus luteum in Group C than in Group L ewes. We conclude that undernutrition impairs steroid receptor expression and binding capacity. This may alter the uterine environment and help explain the reductions in embryo survival.