Factors influencing the success of transcervical insemination in Merino ewes

The experiments described examined the effects of a number of factors on the level of uterine insemination achieved in Merino ewes by a transcervical insemination technique (Guelph system for transcervical artificial insemination; GST-AI). Cervical penetration rate is an important limitation to the use of such methods in Merinos. Simulated insemination was performed to estimate the proportion of ewes in which a pipette could be passed through the cervix to the uterus. In Experiment 1, cervical penetration rate (n = 14 to 30) was unaffected by an increase in postpartum interval at AI from 12 to 26 wk. The results of cervical penetration for individual ewes were found to be repeatable (P < 0.05). Experiment 2 (197 ewes) revealed a clear effect of ewe parity on penetration rates in hormonally synchronized ewes during the nonbreeding season (P < 0.05). In Experiment 3, estrus synchronization using progestagen (n = 51) or prostaglandin (n = 50) did not affect penetration rate. The penetration rate was slightly higher in the naturally cycling ewes, but the difference was not significant. Comparison of ewes from Experiments 2 and 3 suggests the possibility of a major effect of stage of the breeding season on the penetration rate (P < 0.05). It is concluded that ewe selection and management techniques may be used to increase the proportion of transcervical insemination attempts resulting in uterine insemination. However, fertility testing will be required to determine whether such improvements translate into correspondingly increased pregnancy rates.     

Effect of the antiprogestin RU-486 on progesterone inhibition of occupied nuclear estrogen receptor in the uterus

The ability of the antiprogestin, RU-486, to reverse progesterone (P) antagonism of occupied nuclear E receptor retention was studied in the rat and hamster uterus. RU-486 was shown to effectively displace [3H]P binding from rat uterine cytosolic P receptor in in vitro competition assay. In contrast, no competition by RU-486 for [3H]P binding was observed for uterine cytosolic P receptor from the hamster uterus. In the presence of sustained serum levels (silastic implants) of P and estradiol (E), occupied nuclear E receptor was significantly inhibited in the rat uterus. At 6, 12 and 24h after RU-486 treatment (5 mg/animal, s.c.) uterine receptors for E and P were determined. No significant differences in cytosolic E and P receptors were observed between treated (E + P, + RU-486) and control (E + P alone) animals. However, by 6 h following RU-486 treatment, occupied nuclear E receptor retention increased significantly (0.30 +/- 0.05 vs 0.60 +/- 0.09, pmol/uterus) and reached a peak between 12 h (1.32 +/- 0.09) and 24 h (0.83 +/- 0.09). The increase in nuclear E receptor approached the level observed in animals with an E implant alone (1.55 +/- 0.15). Measurement of uterine fluid accumulation following RU-486 treatment showed an increase which paralleled that observed for occupied nuclear E receptor retention. A similar in vivo experiment in the hamster showed no reversal of P inhibition of occupied nuclear E receptor. These results show that: 1. RU-486 is an effective competitor for rat uterine P receptor but not hamster P receptor; 2. RU-486 can rapidly reverse P inhibition of uterine occupied nuclear E receptor in the presence of sustained serum levels of E and P; 3. The recovery of occupied nuclear E receptor is coincident with a resumption of E action (uterine fluid accumulation). The studies also provide a novel means by which antiprogestin activity can be assessed in vivo in the presence of sustained E and P serum levels, e.g. the reversal of P inhibition of uterine nuclear E receptor retention.     

Effects of estradiol and progesterone on the reproductive tract and on uterine sex steroid receptors in female lambs

The effects of estradiol-17 beta (E(2)) and progesterone (P) on the reproductive tract and on uterine estrogen receptors and P receptors were studied in 2-mo-old female lambs (n = 11). On Days 0, 1 and 2, E(2) (1 ug/kg, Group E, n = 4), P (0.3 mg/kg, Group P, n = 4) or corn oil (control) vehicle (Group C, n = 3) were administered, and in Day 3 all lambs were slaughtered. Group E (n = 12) had E(2) serum concentrations (mean +/- SEM) of 43.8 +/- 2.2 pmol L , similar to that of the follicular phase; while P concentrations in Group P (n = 12) were similar (2.8 +/- 0.18 nmol L ) to those of the luteal phase of the ewe estrous cycle. The E(2) treatment increased the reproductive tract weight, while P treatment increased only the uterine weight. Both E(2) and P receptors from upper and middle uterine zones (including the myometrium, endometrium and caruncles) were determined by binding assays with tritiated hormones, dextran-charcoal separation and inverse Scatchard analysis. Both the E(2) and P treatments decreased E(2) and P receptor concentrations in upper and middle zones, although the upper zone had higher receptor concentrations than the middle zone (P < 0.01). E(2) receptor concentrations in the upper zone (mean +/- SEM, fmol mg prot) were 1236 +/- 34, 667 +/- 80 and 444 +/- 103 for Groups C, P and E, respectively. The P receptor concentrations were 2434 +/- 135, 1273 +/- 102 and 1536 +/- 213 for the same groups. The high uterine P receptor concentrations allowed P action without prior estrogen priming of female lambs. The present results suggest that E(2) and P might down-regulate their own and each other's receptors during development. The biological responses induced by E(2) and P, as measured by the reproductive tract weight, demonstrated that at an early stage of development uterine receptors are physiologically active.     

Ovarian response to gonadotropin treatment initiated relative to wave emergence in ultrasonographically monitored ewes

Follicular recruitment and luteal response to superovulatory treatment initiated relative to the status of the first wave of the ovine estrous cycle (Wave 1) were studied. All ewes (n = 25) received an intravaginal progestagen sponge to synchronize estrous cycles, and ewes were monitored daily by transrectal ultrasonography. Multiple-dose FSH treatment (total dose = 100 mg NIH-FSH-P1) was initiated on the day of ovulation (Day 0 group) in 16 ewes. In the remaining 9 ewes, FSH treatment was started 3 d after emergence of the largest follicle of Wave 1 (Day 3 group). Ewes received PGF(2alpha) with the last 2 FSH treatments to induce luteolysis. Daily blood samples were taken to determine progesterone profiles and to evaluate the luteal response subsequent to superovulation. The ovulation rate was determined by ultrasonography and correlated with direct observation of the ovaries during laparotomy 5 to 6 d after superovulatory estrus when the uterus was flushed to collect embryos. Results confirmed that follicular recruitment was suppressed by the presence of a large, growing follicle. In the Day 0 and Day 3 groups, respectively, mean numbers (+/- SEM) of large follicles (>/= 4 mm) recruited were 6.4 +/- 0.6 and 2.7 +/- 0.7 (P < 0.01) at 48 h after the onset of treatment, and 6.7 +/- 0.5 and 5.1 +/- 0.6 (P = 0.08) at 72 h after the onset of treatment. Ovulation rates were 5.6 +/- 0.8 and 3.3 +/- 0.8 in the respective groups (P < 0.05). The number of transferable embryos was 1.8 +/- 0.5 and 0.3 +/- 0.2 in the respective groups (P < 0.05). Short luteal phases (相似文献   

Uterine steroid hormone receptors during the estrous cycle and during hibernation in the Turkish hamster (Mesocricetus brandti)

The Turkish hamster is a long-day breeder that hibernates for 4-5 mo if exposed to a short-day, cold environment. The objective of this study was to assess the uterine responsiveness of the hibernating animal to ovarian steroids. Our approach was 1) to characterize and determine uterine estrogen (E) and progesterone (P) receptors (R) during hibernation as compared to the levels observed in cycling females that had terminated hibernation, and 2) to assess the responsiveness of the uterus to E during hibernation by its ability to induce uterine P receptor. Females were exposed to short days (10L:14D) for 2 mo and then were placed in a cold-room (10L: 14D, 6 +/- 1 degrees C). After 2 or 4 mo in the cold, hibernating animals were killed and uterine steroid receptors were determined by 3H-steroid binding assay. Uterine receptors were also determined in cycling Turkish hamsters on each morning of the estrous cycle. Values for uterine receptors (pmol/g tissue, n = 4-6) during the estrous cycle (estrus, diestrus I, diestrus II, proestrus) were: 4.3 +/- 0.78, 3.9 +/- 0.19, 4.1 +/- 0.25, 3.7 +/- 0.5 for cytosolic ER; 36.6 +/- 5.8, 32.2 +/- 6.8, 36.3 +/- 1.5, 54.4 +/- 1.9 for cytosolic PR; 0.59 +/- 0.11, 0.54 +/- 0.07, 1.06 +/- 0.05, 1.42 +/- 0.17 for nuclear ER. Hibernating (torpid) animals sampled after 2 mo in the cold showed a significant (p less than 0.05) depression of cytosolic ER (2.6 +/- 0.12, n = 5) and cytosolic PR (19.0 +/- 2.6, n = 8) as compared to any day of the estrous cycle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Enzyme activities and protein and carbohydrate concentrations in cervical secretions at dioestrus in normal ewes and ewes with permanent phytooestrogenic infertility

Cervical secretions of clover-affected and control ewes in the luteal phase of the ovarian cycle were obtained by flushing the anterior vagina. The flushings were analysed for proteins, carbohydrates and enzyme activities, and were found to be similar to the secretions of the normal ovine uterus. There was significantly more protein, carbohydrate and acid-soluble glycoprotein but less alkaline phosphatase, N-acetylglycosidases (EC 3.2.1.30 and 3.2.1.53) and ribonuclease I in the vaginal flushings of clover-affected ewes. The observed changes were not due to more inflammation in the cervix of clover-affected ewes as there were fewer bacteria, leukocytes and epithelial cells and no elevation of lysozomal enzyme activities in their flushings. It is suggested that the cervix of the clover-affected ewe behaves as though under a stronger than normal oestrogenic stimulation during dioestrus.     

Uterine oxytocin receptors in an Australian marsupial, the brushtail possum, Trichosurus vulpecula

1. Oxytocin receptors in the uterus of the brushtail possum (T. vulpecula) were characterized by radioreceptor assay and compared with those of the sheep and rat uterus. 2. A single oxytocin binding site was found with an affinity (Kd) and receptor concentration (Ro) of 3.0 +/- 0.8 nmol/l and 200 +/- 60 fmol/mg protein, respectively (SEM; n = 5). The receptor was stable at -20 degrees C; divalent ions were required for optimum binding. 3. Competitive displacement curves with related peptides showed the following order of specificity: vasotocin greater than oxytocin greater than mesotocin = arginine-vasopressin = [Thr4, Gly7]-oxytocin greater than lysine-vasopressin = isotocin much greater than [d(CH2)5, D-Phe2, Ile4, Ala9-NH2]-AVP. 4. It was concluded that oxytocin receptors in the possum have similar characteristics to those of placental mammals.     

Gastrin-releasing peptide (GRP) in the ovine uterus: regulation by interferon tau and progesterone

Gastrin-releasing peptide (GRP) is abundantly expressed by endometrial glands of the ovine uterus and processed into different bioactive peptides, including GRP1-27, GRP18-27, and a C-terminus, that affect cell proliferation and migration. However, little information is available concerning the hormonal regulation of endometrial GRP and expression of GRP receptors in the ovine endometrium and conceptus. These studies determined the effects of pregnancy, progesterone (P4), interferon tau (IFNT), placental lactogen (CSH1), and growth hormone (GH) on expression of GRP in the endometrium and GRP receptors (GRPR, NMBR, BRS3) in the endometrium, conceptus, and placenta. In pregnant ewes, GRP mRNA and protein were first detected predominantly in endometrial glands after Day 10 and were abundant from Days 18 through 120 of gestation. Treatment with IFNT and progesterone but not CSH1 or GH stimulated GRP expression in the endometrial glands. Western blot analyses identified proGRP in uterine luminal fluid and allantoic fluid from Day 80 unilateral pregnant ewes but not in uterine luminal fluid of either cyclic or early pregnant ewes. GRPR mRNA was very low in the Day 18 conceptus and undetectable in the endometrium and placenta; NMBR and BRS3 mRNAs were undetectable in ovine uteroplacental tissues. Collectively, the present studies validate GRP as a novel IFNT-stimulated gene in the glands of the ovine uterus, revealed that IFNT induction of GRP is dependent on P4, and found that exposure of the ovine uterus to P4 for 20 days induces GRP expression in endometrial glands.     

Uteroplacental production of eicosanoids in ovine pregnancy

Dramatic cardiovascular alterations occur during normal ovine pregnancy which may be associated with increased prostaglandin production, especially of uteroplacental origin. To study this, we examined (Exp 1) the relationships between cardiovascular alterations, e.g., the rise in uterine blood flow and fall in systemic vascular resistance, and arterial concentrations of prostaglandin metabolites (PGEM, PGFM and 6-keto-PGF1 alpha) in nonpregnant (n = 4) and pregnant (n = 8) ewes. To determine the potential utero-placental contribution of these eicosanoids in pregnancy, we also studied (Exp 2) the relationship between uterine blood flow and the uterine venous-arterial concentration differences of PGE2, PGF2 alpha, PGFM, 6-keto-PGF1 alpha, and TxB2 in twelve additional late pregnant ewes. Pregnancy was associated with a 37-fold increase in uterine blood flow and a proportionate (27-fold) fall in uterine vascular resistance (p less than 0.01). Arterial concentrations of PGEM were similar in nonpregnant and pregnant ewes (316 +/- 19 and 245 +/- 38 pg/ml), while levels of PGFM and PGI2 metabolite 6-keto-PGF1 alpha were elevated 23-fold (31 +/- 14 to 708 +/- 244 pg/ml) and 14-fold (12 +/- 4 to 163 +/- 78 pg/ml), respectively (p less than 0.01). Higher uterine venous versus uterine arterial concentrations were observed for PGE2 (397 +/- 36 and 293 +/- 22 pg/ml) and 6-keto-PGF1 alpha (269 +/- 32 and 204 +/- 32 pg/ml), p less than 0.05, but not PGF2 alpha or TxB2. Although PGFM concentrations appeared to be greater in uterine venous (1197 +/- 225 pg/ml) as compared to uterine arterial (738 +/- 150 pg/ml) plasma, this did not reach significance (0.05 less than p less than 0.1). In normal ovine pregnancy arterial levels of PGI2 are increased, which may in part reflect increased uteroplacental production. Moreover the gravid ovine uterus also appears to produce PGE2 and metabolize PGF2 alpha.     

Suppression of oxytocin-induced prostaglandin F2alpha release after intra-uterine nordihydroguariaretic acid administration in ewes

Intrauterine administration of the 5-lipoxygenase inhibitor nordihydroguariaretic acid (NDGA; 5 mg, bid) on Days 9-14 of the ovine estrous cycle (estrus = Day 0) delayed luteolysis and extended the duration of the estrous cycle (20+/-1, SD, vs. 16+/-1 days; P < 0.01). In control ewes, plasma concentrations of 13,14,dihydro-15-keto prostaglandin F2alpha increased significantly (P < 0.001) following i.v. administration of oxytocin (10 i.u.) on Day 14; in the nordihydroguariaretic acid-treated ewes, however, there was no such increase. In addition, concentrations of endometrial oxytocin receptors were significantly less (P < 0.01) in the nordihydroguariaretic acid-treated ewes (218+/-60 vs. 579+/-66 fmol/mg tissue). These results suggest that 5-lipoxygenase products of arachidonate metabolism may be involved in the control of ovine luteal function.     

Relationship between dilatation of the rat uterine cervix and a small dermatan sulfate proteoglycan

Cervical linear circumference (lo), extensibility and rate of creep, and the content and concentration of collagen and proteoglycans were determined on uterine cervices of rats at different reproductive stages. The inner circumference increased from 9 +/- 3 (SD) mm at the nongravid stage to a maximum of 41 +/- 5 mm at term; a significant drop to 23 +/- 2 mm occurred by 4 h postpartum with a further drop to 18 +/- 4 mm by 1 day postpartum. The extensibility and rate of creep reached their maxima 1 day before term and returned to the nongravid value by 1 day postpartum. The small (Mr = 95,000) type II dermatan sulfate proteoglycan, the major cervical proteoglycan, increased from 43 +/- 6 micrograms per cervix at the nongravid stage to 196 +/- 33 micrograms at term. The amount of this proteoglycan decreased significantly by 35% to 126 +/- 5 micrograms within 4 h postpartum and declined further to 79 +/- 16 micrograms by 1 day postpartum. The total cervical collagen content increased less than 2-fold during pregnancy, from 3.5 +/- 0.5 to 6.3 +/- 0.7 mg; a decline to 5.8 mg by 1 day postpartum was not significant. The ratio of small proteoglycan: collagen increased 2.5-fold between the nongravid state and term, then returned to the nongravid value by 1 day postpartum. Significant correlations were found between the lo and the amount of small proteoglycan per cervix (r = 0.86; n = 69) and between lo and the ratio of small proteoglycan:collagen (r = 0.83; n = 50) when data from every reproductive stage were combined. A mechanism is proposed whereby the interaction of the proteoglycan with collagen fibers might alter mechanical properties and contribute to cervical dilatation and its rapid reversal.     

Interferon-tau and progesterone regulate ubiquitin cross-reactive protein expression in the ovine uterus

Ubiquitin cross-reactive protein (UCRP) is a functional ubiquitin homolog synthesized by the ruminant endometrium in response to conceptus-derived interferon-tau (IFNtau). Progesterone is required for IFNtau to exert antiluteolytic actions on the endometrium. Therefore, this study was designed to determine whether progesterone is requisite for IFNtau induction of UCRP expression within the ovine uterus. Cyclic ewes were ovariectomized and fitted with intrauterine (i.u.) catheters on Day 5 and treated daily with steroids (i.m.) and protein (i.u.) as follows: 1) progesterone (P, Days 5-24) and control serum proteins (CX, Days 11-24); 2) P and ZK 137.316 (ZK; progesterone receptor antagonist, Days 11-24) and CX proteins; 3) P and recombinant ovine IFNtau (roIFNtau, Days 11-24); or 4) P and ZK and roIFNtau. All ewes were hysterectomized on Day 25. In P-treated ewes, roIFNtau increased endometrial UCRP mRNA and protein levels. However, administration of ZK to ewes ablated roIFNtau induction of UCRP. Recombinant ovine IFNtau induced expression of UCRP mRNA in progestinized endometrial luminal (LE) and glandular (GE) epithelium as well as in both stratum compactum and spongiosum layers of the stroma (ST). Progesterone receptor protein was located in endometrial ST, but not in LE and GE from these ewes. Results support the hypothesis that progesterone is required for IFNtau induction of type I IFN-responsive genes, such as UCRP, in the ruminant uterus.     

Ovine placental lactogen specifically binds to endometrial glands of the ovine uterus

A hormonal servomechanism has been proposed to regulate differentiation and function of the endometrial glandular epithelium (GE) in the ovine uterus during pregnancy. This mechanism involves sequential actions of estrogen, progesterone, ovine interferon tau (IFNtau), placental lactogen (oPL), and placental growth hormone (oGH). The biological actions of oPL in vitro are mediated by homodimerization of the prolactin receptor (oPRLR) and heterodimerization of the oPRLR and oGH receptor. The objectives of the study were to determine the effects of intrauterine oPL, oGH, and their combination on endometrial histoarchitecture and gene expression and to localize and characterize binding sites for oPL in the ovine uterus in vivo using an in situ ligand binding assay. Intrauterine infusion of oPL and/or oGH following IFNtau into ovariectomized ewes treated with progesterone daily differentially affected endometrial gland number and expression of uterine milk proteins and osteopontin. However, neither hormone affected PRLR, insulin-like growth factor (IGF)-I, or IGF-II mRNA levels in the endometrium. A chimeric protein of placental secretory alkaline phosphatase (SEAP) and oPL was used to identify and characterize binding sites for oPL in frozen sections of interplacentomal endometrium from pregnant ewes. Specific binding of SEAP-oPL was detected in the endometrial GE on Days 30, 60, 90, and 120 of pregnancy. In Day 90 endometrium, SEAP-oPL binding to the endometrial GE was displaced completely by oPL and prolactin (oPRL) but only partially by oGH. Binding experiments using the extracellular domain of the oPRLR also showed that iodinated oPL binding sites could be competed for by oPRL and oPL but not by oGH. Collectively, results indicate that oPL binds to receptors in the endometrial glands and that oPRL is more effective than oGH in competing for these binding sites. Thus, effects of oPL on the endometrial glands may be mediated by receptors for oPRL and oGH.     

Direct effects of estradiol-17 beta on the number of gonadotropin-releasing hormone receptors in the ovine pituitary

Concentrations of pituitary receptors for gonadotropin-releasing hormone (GnRH) are affected by GnRH and gonadal steroids. To test the hypothesis that estradiol-17 beta (E2) directly affects the number of GnRH receptors in the pituitary, independent of GnRH secretion, ovariectomized ewes with hypothalamic-pituitary disconnections (HPD) were given 25 micrograms (i.m.) of E2 (HPD + E2, n = 5) or oil (HPD + OIL, n = 5). Ovariectomized control ewes, with intact hypothalamic-pituitary axes (INT), also received either E2 or oil (INT + E2, n = 6; INT + OIL, n = 6). Blood samples were taken hourly for analysis of serum concentrations of luteinizing hormone (LH) from 4 h prior to until 16 h after treatment. Pituitaries were collected 16 h after treatment for analysis of GnRH receptors. Treatment with E2 increased concentrations of LH in serum beginning 12.7 +/- 0.6 h after injection in INT ewes but not in HPD ewes. Compared to INT + OIL ewes, E2 treatment increased (p less than 0.001) the number of GnRH receptors by 2.5-fold in INT ewes and by 2.0-fold in HPD ewes. These results suggest that although GnRH is necessary for secretion of gonadotropins, E2 alone can directly increase the number of GnRH receptors in the pituitary.     

Gonadotropin-releasing hormone secretion during the postpartum anestrous period of the ewe

An increase in episodic release of LH is putatively the initial event leading to the onset of postpartum ovarian cyclicity in ewes. This experiment was conducted to determine the relationship between hypothalamic release of GnRH and onset of pulsatile secretion of LH during postpartum anestrus. Control ewes (n = 7) were monitored during the postpartum period to determine when normal estrous cycles resumed. In controls, the mean interval from parturition to the first postpartum estrus as indicated by a rise in serum progesterone greater than 1 ng/mg was 25.8 +/- 0.6 days. Additional ewes (n = 4-5) at 3, 7, 14, and 21 days postpartum (+/- 1 day) were surgically fitted with cannula for collection of hypophyseal-portal blood. Hypophyseal-portal and jugular blood samples were collected over a 6- to 7-h period at 10-min intervals. The number of GnRH pulses/6 h increased (p less than 0.05) from Day 3 postpartum (2.2 +/- 0.5) to Days 7 and 14 (3.6 +/- 0.2 and 3.9 +/- 0.4, respectively). A further increase (p less than 0.05) in GnRH pulse frequency was observed at Day 21 postpartum (6.4 +/- 0.4 pulses/6 h). Changes in pulsatile LH release paralleled changes observed in pulsatile GnRH release over Days 3, 7, 14, and 21 postpartum (0.83 +/- 0.3, 2.8 +/- 0.4, 2.9 +/- 0.6, and 4.0 +/- 1.1 pulses/6 h, respectively). GnRH pulse amplitude was higher at Day 21 than at Days 3, 7, or 14 postpartum. These findings suggest that an increase in the frequency of GnRH release promotes the onset of pulsatile LH release during postpartum anestrus in ewes.     

Cervical dilation, conception rate, and concentrations of progesterone and estradiol-17B in postpartum ewes treated with porcine relaxin

Experiments were conducted to determine the effects of porcine relaxin (pRLX) on cervical dilation and conception rates in postpartum ewes. In Experiment 1, ewes received medroxyprogesterone acetate (MAP) sponge on day 16 (day 0 = lambing) and 750 IU pregnant mare serum gonadotropin (PMSG) at sponge removal on day 30. Control ewes received saline and relaxin-treated (RLX) ewes received 0.5 mg pRLX (>/= 3000 U/mg) i.m. at 24 h and 1.0 mg pRLX at 36 h after PMSG. All ewes were inseminated (Al) at 55 h after PMSG with 0.4 ml fresh semen. The proportion of RLX treated ewes (6 6 ) in which the cervix was penetrated was greater (P < 0.05) than in Control ewes (0 5 ). However, ova recovery rate was lower (P < 0.05) for RLX ewes (1 6 ) than for control ewes (5 5 ). In Experiment 2, ewes between Days 90 to 120 post partum received MAP sponges for a period of 8 d and 750 IU PMSG at sponge removal. Control ewes (n = 9) received saline; RLX-1 ewes (n = 8) received 0.5 mg pRLX at 24 h and an additional 0.5 mg pRLX at 36 h after PMSG; and RLX-1.5 ewes (n = 9) received 0.5 mg pRLX at 24 h and an additional 1.0 mg pRLX at 36 h after PMSG. Ewes were mated to rams at estrus, and cervical dilation was checked at 55 h after PMSG. The cervix could not be penetrated in any of the ewes. Conception rates on Day 26 were 66, 56 and 63% for control, RLX-1 and RLX-1.5 groups, respectively. These results demonstrate that the effect of relaxin on cervical dilation and conception rate is dependent upon the postpartum stage of the ewes.     

Progesterone regulates FGF10, MET, IGFBP1, and IGFBP3 in the endometrium of the ovine uterus

Progesterone (P4) is unequivocally required to maintain a uterine environment conducive to pregnancy. This study investigated the effects of P4 treatment on expression of selected growth factors (fibroblast growth factor 7 [FGF7], FGF10, hepatocyte growth factor [HGF], and insulin-like growth factors [IGF1 and IGF2]), their receptors (MET, FGFR2(IIIB), and IGF1R), and IGF binding proteins (IGFBPs) in the ovine uterus. Ewes received daily injections of corn oil vehicle (CO) or 25 mg of P4 in vehicle from 36 h after mating (Day 0) to hysterectomy on Day 9 or Day 12. Another group received P4 to Day 8 and 75 mg of mifepristone (RU486, a P4 receptor antagonist) from Day 8 through Day 12. Endometrial FGF10 mRNA levels increased between Day 9 and Day 12 and in response to P4 on Day 9 in CO-treated ewes, which had larger blastocysts, and were substantially reduced in P4+RU486-treated ewes, which had no blastocysts on Day 12. Endometrial FGF7 or HGF mRNA levels were not affected by day or reduced by RU486 treatment, but MET mRNA levels were higher in P4-treated ewes on Day 9 and Day 12. Levels of IGF1, IGF2, and IGF1R mRNA in the endometria were not affected by early P4 treatment. Although stromal IGFBPs were unaffected by P4, levels of IGFBP1 and IGFBP3 mRNA in uterine luminal epithelia were increased substantially between Day 9 and Day 12 of pregnancy in CO-treated ewes and on Day 9 in early P4-treated ewes. Therefore, FGF10, MET, IGFBP1, and IGFBP3 are P4-regulated factors within the endometrium of the ovine uterus that have potential effects on endometrial function and peri-implantation blastocyst growth and development.     

Effects of melengestrol acetate and P.G. 600 on fertility in Rambouillet ewes outside the natural breeding season

The effects of melengestrol acetate (MGA) and P.G. 600 on ewe fertility outside the natural breeding season were evaluated. Rambouillet ewes were assigned to one of four groups: (1) control (C; n=92); (2) PG600 (n=86); (3) MGA (n=99); and (4) MGA+PG600 (n=92). A pellet with or without MGA (0.3mg/ewe/d) was fed at 0.15kg/ewe/d for 7d. On the last day of pellet feeding, ewes were given either saline or 5mL of P.G. 600 i.m. (400IU equine chorionic gonadotropin (eCG) and 200IU human chorionic gonadotropin (hCG)). Ultrasonography was performed between Days 20 and 25 of gestation for ewes that were mated during the first 6 d of the breeding period from the MGA (n=15) and MGA+PG600 (n=8) groups, and the number of luteal structures and embryos were counted. During the first 6d of the breeding period, MGA increased (P<0.05) the percentage of ewes that mated and conceived when compared to C and PG600 (24.2% vs. 3.3% and 10.5%, respectively). Relative to MGA, the mean (+/-S.E.M.) number of luteal structures per ewe was enhanced (P<0.03) in MGA+PG600 (1.53+/-0.13 vs. 2.38+/-0.42, respectively), however as pregnancy progressed, the number of embryos (1.5+/-0.13 vs. 1.8+/-0.16, respectively) and lambs born (1.3+/-0.15 vs. 1.5+/-0.27, respectively) did not differ. Treatment with MGA reduced (P<0.01) the interval from ram introduction to lambing relative to groups that did not receive MGA (168+/-0.8d vs. 171+/-0.6d, respectively). In conclusion, treatment with MGA increased the percentage of ewes conceiving early in the breeding period. Although P.G. 600 increased the number of luteal structures present per ewe, it did not significantly enhance ewe prolificacy.     

Estrogen and progesterone receptor content in the pituitary gland and uterus of progesterone-primed and gonadotropin releasing hormone-treated anestrous ewes

The objective of this work was to investigate the effect of progesterone (P) and gonadotropin-releasing hormone (GnRH) treatment on estrogen receptor (ER) and P receptor (PR) concentrations in the pituitary gland and uterus of anestrous ewes. Ewes were either not treated (group C, n = 4); were treated with 0.33 g P-controlled internal drug release (P-CIDR) for 10 days (group P, n = 4), with GnRH, 6.7 ng i.v. injections every 2 h for 18 h followed by a 4 microg bolus administration of Receptal at 20 h (group GnRH, n = 4), or with a combination of the P and GnRH treatment (group P + GnRH, n = 3). Ewes were humanely killed either at the beginning of the experiment (group C), when the CIDR was removed (group P), or 24 h after the GnRH bolus treatment (groups GnRH and P + GnRH). Progesterone treatment increased serum P concentrations, indicating that the treatment was effective. All GnRH treated ewes had similar luteinizing hormone (LH) surges, which lasted 8 h. At slaughter, estradiol (E2) concentrations in the GnRH group were higher than in groups C, P, and P + GnRH. Treatment with GnRH increased more than 10-fold the content of ER and PR in the pituitary gland without altering steroid receptor concentrations in the uterus. When GnRH was combined with P the uterine receptor contents were higher than with P treatment alone. The treatment with P decreased ER and PR content in the uterus, but had no effect on the pituitary gland. The results show that regulation by P and GnRH of ER and PR content in anestrous ewes is tissue-specific.