Effects of dibuturyl cAMP, LHRH, and aromatase inhibitor on simultaneous outputs of prostaglandin F2α, and 13,14-dihydro-15-keto-prostaglandin F2α by term placental explants

Explants from term human placentas were maintained in culture with daily changes of medium. Daily output of PGF_2α and PGFM¹ decreased during the course of the incubation. Addition of 4 μg/ml DHEAS or 67 μg/ml LDL cholesterol had no effect on output of PGF_2α or PGFM. Addition of 1.6, 3.2, or 6.4 μg/ml of LHRH to the culture plates had no effect on output of PGFM or PGF_2α, but LHRH increased hCG output. Dibutyryl cAMP (1mM, 2mM, and 4mM) increased output of PGF_2α, PGFM, and hCG. Aromatase inhibitor decreased hCG output, but it was without effect on output of PGF_2α, or PGFM. Significant correlations were demonstrated between progesterone, PGFM, PGF_2α, and hCG, suggesting that PGF_2α originates in the syncytiotrophoblast cell. The ability of LHRH to stimulate output of hCG but not PGF_2α while dbcAMP stimulated both suggests that either PGF_2α and hCG arise in different cells or that LHRH does not act through cAMP.     

Stimulation of leydig cell testoterone secretion in vitro and in vivo in hypophysectomized rats by an agonist of luteinizing hormone releasing hormone

Injection of a luteinizing hormone-releasing hormone (LHRH) agonist into 55-day-old male rats which had been hypophysectomized 3 days earlier resulted in a 10- to 30-fold increase in the levels of testosterone in serum and testicular interstitial fluid (IF) in the 4h following injection. The levels achieved were within or above the normal range for intact untreated rats of this age. In similar animals, injection of LHRH agonist also enhanced the serum testosterone response to injected hCG at $\text{1}\text{1}\text{2}\text{h}$, but not at later times after injection, and by 24h reduced IF levels of testosterone suggested that LHRH agonist had begun to inhibit stimulation by hCG. $\text{In vitro}$, dispersed Leydig cells from untreated hypophysectomized rats showed a 2-fold increase in testosterone responsiveness to LHRH agonist when compared to cells from intact rats, and this change was associated with an 80% increase in the number of Leydig cell LHRH-receptors.     

Distribution of luteinizing hormone-releasing hormone receptors in the rat ovary

The distribution of luteinizing hormone-releasing hormone (LHRH) receptors was studied in the adult rat ovary using autoradiography after injection of the stable LHRH agonist ¹²⁵I-labelled [D-Ser(TBU)⁶,des-Gly-NH₂¹⁰]LHRH ethylamide (Buserelin) and by radioreceptor assay using the same tracer. In intact cycling female rats, no differences in ovarian LHRH receptor levels could be observed between day diestrus I and day proestrus. Moreover, similar levels are observed in total ovarian homogenate, corpora lutea and the remaining ovarian tissue in adult animals treated with PMSG (pregnant mare's serum gonadotropins) and hCG (human chorionic gonadotropin). Radioautographic data show a comparable distribution of grains over theca interna and externa, granulosa and luteal cells. The present findings indicate the presence of LHRH receptors in both the interstitial and follicular cells throughout all stages of cellular differentiation.     

A comparison of PMSG and LHRH agonist treatment in the induction of ovulation in the anoestrous ewe

The aim of this experiment was to compare the use of pregnant mares' serum gonadotrophin (PMSG) with that of a luteinizing hormone releasing hormone (LHRH) agonist in the induction of ovulation in anoestrous sheep. Anoestrous ewes were treated with progestagen-impregnated sponges for 12 days. They were given either PMSG at the time of sponge withdrawal or the LHRH agonist D-Ser(But)⁶desGlyNH₂¹⁰LHRH ethylamide 20 h after sponge withdrawal. This protocol was followed over 2 consecutive years. Plasma concentrations of oestradiol and LH were measured, and in the first year a comparison was made of the ovulation rate, conception rate and luteal function of the two groups after artificial insemination. During the first year, all of the PMSG-treated group but none of the agonist-treated group exhibited oestrus. Five of the eight PMSG-treated ewes had embryos in utero at slaughter whilst none was present in the agonist-treated ewes. The secretion of progesterone was greatest in the PMSG-treated ewes (P < 0.001). During the second year, a more frequent blood-sampling regime was employed. Increased plasma concentrations of LH occurred within 3 h of agonist administration. Plasma oestradiol concentrations peaked at 20 h and 45 h after sponge withdrawal in both groups. Both peaks were larger in the agonist-treated group. It is concluded that a single dose of the highly potent LHRH agonist is unable to produce normal luteal function or conception using the present protocol.     

Relationship between maternal plasma progesterone concentration and interferon-tau synthesis by the conceptus in cattle

The objective of this study was to determine the relationship between maternal progesterone concentration and conceptus synthesis of interferon-tau as an index of conceptus viability at the time of maternal recognition of pregnancy. Heifers of mixed beef breeds were randomly assigned to receive 1 of 2 treatments: 1) intramuscular injection of 1500 IU hCG on Day 5 after artificial insemination (AI; n = 12) or 2) intramuscular injection of saline on Day 5 after AI (n = 17). Ovaries were scanned daily by transrectal real-time ultrasonography. Progesterone concentrations were determined from daily blood samples collected from the jugular vein. Heifers were slaughtered on Day 18 after AI and conceptus tissues were collected. These were incubated individually at 37 degrees C in RPMI medium, and supernatant collected after 24 h. Conceptus secretory products in the supernatant were analyzed for interferon concentration by antiviral assay using vesicular stomatitis virus. Transrectal ultrasonography showed all heifers that received hCG had at least 1 extra corpus luteum (CL) in addition to the spontaneous CL formed from the previous ovulation (10 with 2 CL, 2 with 3 CL). A significant increase in plasma progesterone concentration was detected in pregnant heifers treated with hCG (n = 9) vs pregnant control heifers (n = 11; P < 0.001). There was a tendency for an increase (P = 0.059) in synthesis of interferon-tau by conceptuses from hCG-treated heifers compared to control heifers. Maternal plasma progesterone concentrations were correlated with interferon-tau production by the conceptuses (r = 0.593, P < 0.006), suggesting that higher maternal progesterone may provide a more suitable environment for the developing conceptus.     

Effect of an LHRH Analog on Growth and Hormone Receptor Levels in DMBA-Induced Mammary Tumors in the Rat

Abstract

Dimethylbenz(a)anthracene (DMBA)-induced mammary tumors in the rat are well known to be hormono-dependent. Daily injections of an LHRH agonist, [D-Ala⁶, des-Gly-NH₂¹⁰]LHRH ethylamide (LHRH-A), 1 ug daily, for 38 days results in a 35% decrease in the number of tumors present at the beginning of the experiment compared to a decline of 45% after ovariectomy and of 8% in the control group. This is accompanied by a marked reduction in ovarian LH and FSH receptors. LHRH-A treatment also resulted in reduction in the number of progesterone and prolactin receptors in the tumors. In addition, an increase in plasma LH and FSH and a decline in plasma prolactin (PRL) concentrations are observed. The mechanisms by which the LHRH agonist induces its antitumoral effect probably relate to an ovarian desensitization to LH and FSH with a concomitant decrease in circulating levels of estrogen and prolactin, two well known stimuli for the growth of DMBA-induced mammary tumors.     

Further characterization of the direct inhibitory effect of LHRH agonists at the testicular level in the rat

To further clarify the relative importance of the pituitary and gonadal sites of LHRH action, intact and hypophysectomized adult male rats were treated with hCG for 7 days, in the presence or absence of simultaneous treatment with increasing doses of the LHRH agonist [D-Ser(TBU)6des-Gly-NH2(10)]LHRH ethylamide, Buserelin (0.025, 0.25, 2.5 or 25 micrograms/rat, twice daily). Daily treatment of intact adult rats with hCG (25 IU) markedly increased ventral prostate and seminal vesicle weight, while a dose-dependent inhibition of the effect was observed following combined administration of Buserelin. In hypophysectomized rats, treatment with hCG resulted in a partial restoration of ventral prostate and seminal vesicle weight, while combined treatment with a high dose of the LHRH agonist (25 micrograms, twice daily) partially (P less than 0.05) inhibited the stimulatory effect of hCG. LH/hCG receptors were almost completely inhibited after hCG injection alone and a further decrease was observed in the presence of simultaneous LHRH agonist treatment. The hCG-induced stimulation of GH/PRL receptors was counteracted by Buserelin treatment in hypophysectomized animals. The present data demonstrate that although LHRH-induced LH release has been shown to play a major role in the loss of testicular functions induced by low doses of LHRH agonists in the rat, a direct inhibitory action of LHRH agonists can be exerted at the testicular level at high doses of the peptide.     

Hormonal secretion in male rats chronically treated with [D-Trp6, Pro9-NEt]-LRF.

Chronic daily administration of the LRF agonist [DTrp⁶, Pro⁹NEt]LRF (A) was accompanied by a blunting of the LH, FSH and testosterone responses. However, plasma LH levels continued to be elevated with each injection, while plasma FSH values remained within control range. As a result, LH/FSH ratios of treated rats were higher than those of control animals. Preinjection plasma testosterone levels were significantly lowered. Repeated injections of A were usually accompanied by increases in plasma progesterone levels which were largest on the second day of qd administration schedules. The intermittent administration of A every 2nd, 3rd or 4th day resulted in continued large increases in plasma progesterone concentrations. These results suggest that the periodically elevated secretion of progesterone and/or LH in the presence of lowered levels of circulating testosterone, may play a role in the paradoxical antigonadal effects of LRF agonists.     

Dissociation of copulation from ovulation in pregnant rabbits

Experiments were designed to determine why copulation in the pregnant rabbit does not terminate pregnancy while treatment with ovulatory doses of luteinizing hormone (LH) human chorionic gonadotropin (hCG) or luteinizing hormone-releasing hormone (LHRH) is known to do so. Pregnant rabbits (Day 8) were mated or were injected with hCG (25 IU/doe) or LHRH (1, 10 micrograms/kg). Serial blood samples were collected over the next 72 h and analyzed for content of LH, follicle-stimulating hormone (FSH) and progesterone. At sacrifice, uteri and ovaries from these animals were examined for viability of the embryos and for signs of recent ovulation. Injection of hCG or LHRH into pregnant animals led to ovulation and to patterns of LH, FSH and progesterone secretion like those which precede ovulation in estrous rabbits. However, mating the pregnant does did not lead to ovulation or to any changes in the circulating hormones. To investigate whether the elevated levels of progesterone during pregnancy were responsible for the dissociation of coitus from ovulation, nonpregnant rabbits were injected with progesterone (2 mg/kg) and then mated or injected with hCG or LHRH. In virtually every respect, the numbers of ovulations and the patterns of hormone secretion in the progesterone-treated, nonpregnant rabbits mimicked those observed in the 8-day pregnant animals; injection of hCG or LHRH caused ovulation and hormonal surges while hCG caused ovulation only. Mating did not lead to ovulation or any change in blood levels of LH, FSH or progesterone. Taken together, the results show that the elevated circulating levels of progesterone, characteristic of pregnancy, are probably responsible for the dissociation of copulation from gonadotropin release in pregnant rabbits.     

孕激素及人绒毛促性腺激素与药物流产后异常子宫出血的关系

目的:分析孕激素和人绒毛膜促性腺激素(h CG)与药物流产后异常子宫出血的关系。方法:选择2017年1月至2017年12月我院妇产科收治的药物终止妊娠的妇女150例,患者口服米非司酮配伍米索前列醇药物终止早期妊娠。将药物流产后子宫出血时间≤14 d作为对照组(n=75),14d作为异常组(n=75)。比较两组患者在药物流产后10 d、14 d、18 d、22 d血清中孕激素和h CG含量,分析两组患者孕激素和h CG含量相关性。结果:两组患者在年龄、月经周期、孕次、受孕天数、体重等方面比较无统计学差异(P0.05)。异常组在药物流产后10 d、14 d、18 d、22 d血清孕激素和h CG含量均高于对照组(P0.05)。两组患者在药物流产后10 d、14 d、18 d、22 d孕激素含量呈先降低再升高的趋势(P0.05)。对照组患者在药物流产后10 d、14 d、18 d、22 d血清hCG含量逐渐降低(P0.05);异常组在药物流产后10 d、14 d血清h CG含量比较无统计学差异(P0.05),在药物流产后18 d、22 d血清hCG含量低于药物流产后10 d、14 d,且药物流产后22 d低于药物流产后18 d(P0.05)。对全部样本的全部时点数据合并进行Pearson相关检验分析,孕激素和h CG含量呈正相关关系(P0.05)。结论:药物流产后异常子宫出血妇女血清的孕激素、hCG含量较高,两者呈正相关关系。药物流产后10 d、14 d监测血清HCG值无明显下降提示有异常子宫出血的可能,联合监测孕激素、hCG含量有利于药物流产后异常子宫出血的预测和治疗。     

Modulation of cyclic AMP formation and progesterone secretion by human chorionic gonadotropin, epinephrine, buserelin and prostaglandins in normal or human chorionic gonadotropin desensitized rat immature luteal cells in monolayer culture

It is now well recognized that hCG-induced luteolysis is associated with hCG-induced desensitization, but the physiological significance of luteal cell GnRH, PGs and beta-receptors is still undefined. Therefore, we intend in this study to observe the effects of prostaglandin F2 alpha and prostaglandin E2 and the interactions between epinephrine, a potent LHRH agonist [(D-Ser-(TBu)6, des-Gly-NH10(2) LHRH ethylamide: Buserelin] and hCG in normal and in vitro hCG-desensitized rat immature luteal cells in monolayer culture, on basal, hCG or cholera toxin stimulated intracellular and extracellular cAMP and progesterone secretion. The present report shows that incubation of immature rat luteal cells in monolayer culture with Buserelin, led to 25-50% inhibition of the epinephrine-as well as PGE2-induced cAMP and progesterone responses. The LHRH agonist can also reverse the stimulatory effects of cholera toxin in the presence of hCG and led with PGF2 alpha, to additive inhibitory effects on extracellular cAMP accumulation induced by cholera toxin. Both Buserelin and PGF2 alpha can reverse the hCG-induced cAMP and progesterone release but no effect could be observed when the incubation was carried out with either substance in the absence of hCG. Prostaglandin E2, in acute conditions of incubation, seems to share agonist properties with hCG when both were incubated with luteal cells. Buserelin reversed the stimulatory effects of PGE2, hCG, epinephrine and cholera toxin on cAMP and progesterone responses to these substances. These results suggest that Buserelin and PGF2 alpha have luteolytic-like effects and that there may be a complementary action for the two substances. Preincubation of rat luteal cells in monolayer culture with 1 nM hCG for a 24 h period led to the inhibition of cAMP and progesterone responses after a subsequent exposure to hCG and epinephrine. Luteal cells were no longer responsive to hCG while the presence of epinephrine in hCG-desensitized cells led to a 40% stimulation of cAMP and progesterone production. These observations suggest that occurred a partial alteration of the N component activity of the adenylyl cyclase system.     

Effects of estrogen and progesterone on LHRH release from a hypothalamic synaptosomal fraction of ovariectomized rats

Mitochondrial-synaptosomal fractions (P₂) from the basomedial hypothalamus of adult ovariectomized rats were employed to study the effects of estradiol benzoate (EB) and progesterone (P) on the release of luteinizing hormone-releasing hormone (LHRH). Treatment of ovariectomized rats with 5 or 50 g of EB significantly reduced the total LHRH released from P₂ under both control and K⁺-stimulated conditions. Furthermore, rats given 50 g EB demonstrated cyclic variations in the magnitude of inhibition of LHRH release. Comparison of LHRH release from P₂ of rats sacrificed at 0900 hr with that from those sacrificed at 1500 hr revealed a small persistent facilitation of LHRH release each afternoon. This facilitation, associated with an increase in the soluble component of LHRH release, was absent when rats also received 5 mg of P. No effects on LHRH release were observed when 17-estradiol alone or when P was applied to P₂ in vitro. The data show that the regulatory effects of estrogen and progesterone given in vivo on LHRH secretion can be observed in a subcellular fraction of the hypothalamus containing neurosecretory cell terminals.Supported by grants from the NIH, HD08389 and NS11753.U.S.P.H.S. Career Development Awardee, K04-HD00022     

Leydig cell receptors for luteinizing hormone releasing hormone and its agonists and their modulation by administration or deprivation of the releasing hormone

Leydig cells isolated from adult rat testes bound ¹²⁵I-labelled luteinizing hormone releasing hormone (LHRH) agonist with high affinity (K_A=1.2 × 10⁹M) and specificity. LHRH and the 3–9 and 4–9 fragments of LHRH agonist competed for binding sites with ¹²⁵I-LHRH agonist but with reduced affinities, whereas fragments of LHRH, and oxytocin and TRH were largely inactive. Somatostatin inhibited binding at high (10^?4M) concentrations but was inactive at 10^?6M and less. Pretreatment of rats for 7 days with 5 μg/day of LHRH agonist reduced binding of ¹²⁵I-LHRH agonist to Leydig cells $\text{in vitro}$ by 25%, whilst inhibition of endogenous LHRH by antibodies for 7 days caused a 40% decrease.     

Studies of inhibition of the luteinizing hormone-releasing hormone by an irreversible inhibitor at the receptor site

[Leu², Leu³, D-Ala⁶]-LHRH is an analog of pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH₂ (LHRH) and inhibits the release of LH and FSH induced by LHRH. This analog and inhibitor has been modified with the objective of developing an active-site-directed irreversible inhibitor. The modification consisted of replacing < Glu¹ with Chl¹ which is the moiety of chlorambucil (a nitrogen mustard). The Chl analog inhibited the release of LH and FSH by LHRH after addition prior to LHRH and after three changes of the incubation medium; in contrast, [Leu², Leu³, D-Ala⁶]-LHRH and [des-His²]-LHRH only inhibit release when added together with LHRH. The Chl analog released LH and FSH but not TSH or GH, indicating that its agonist and antagonist activities could be specific at the receptor site for LHRH.     

Binding of luteinizing hormone-releasing hormone analogues to dispersed rat pituitary cells

The binding of luteinizing hormone-releasing hormone (LHRH) to dispersed rat pituitary cells was studied by using ¹²⁵I-labeled analogues of the neurohormone: a superactive agonist [D Ser (Bu^t)⁶]LHRH(1–9) ethylamide and an antagonist DpGlu¹, DPhe², DTrp^3,6-LHRH. Although these cells were exposed to proteolytic enzymes, their ability to respond to LHRH stimulation by gonadotropin release, is preserved. The time course of binding of the two analogues at different temperatures has demonstrated that highest specific binding is evident at 4°C and that equilibrium is reached after 90 min of incubation at this temperature. Incubation of pituitary cells with the labeled analogues together with increasing concentrations of LHRH or unlabeled analogues exhibited parallel competition curves, suggesting binding to the same receptor sites but with different affinities. Biologically inactive analogues of LHRH or unrelated peptides such as TRH did not compete for binding sites. K_a values for the agonist, LHRH and the antagonist were 2.1 × 10⁹M^?1, 0.92 × 10⁸M^?1 and 0.76 × 10⁹M^?1, respectively, and the binding capacity was 116 fmoles/10⁶ pituitary cells.     

Pituitary and ovarian hormone secretion and ovulation in gilts injected with gonadotropins during and after oral administration of progesterone agonist (Altrenogest)

We determined changes in plasma hormone concentrations in gilts after treatment with a progesterone agonist, Altrenogest (AT), and determined the effect of exogenous gonadotropins on ovulation and plasma hormone concentrations during AT treatment. Twenty-nine cyclic gilts were fed 20 mg of AT/(day X gilt) once daily for 15 days starting on Days 10 to 14 of their estrous cycle. The 16th day after starting AT was designated Day 1. In Experiment 1, the preovulatory luteinizing hormone (LH) surge occurred 5.6 days after cessation of AT feeding. Plasma follicle-stimulating hormone (FSH) increased simultaneously with the LH surge and then increased further to a maximum 2 to 3 days later. In Experiment 2, each of 23 gilts was assigned to one of the following treatment groups: 1) no additional AT or injections, n = 4; 2) no additional AT, 1200 IU of pregnant mare's serum gonadotropin (PMSG) on Day 1, n = 4); 3) AT continued through Day 10 and PMSG on Day 1, n = 5, 4) AT continued through Day 10, PMSG on Day 1, and 500 IU of human chorionic gonadotropin (hCG) on Day 5, n = 5; or 5) AT continued through Day 10 and no injections, n = 5. Gilts were bled once daily on Days 1-3 and 9-11, bled twice daily on Days 4-8, and killed on Day 11 to recover ovaries. Termination of AT feeding or injection of PMSG increased plasma estrogen and decreased plasma FSH between Day 1 and Day 4; plasma estrogen profiles did not differ significantly among groups after injection of PMSG (Groups 2-4). Feeding AT blocked estrus, the LH surge, and ovulation after injection of PMSG (Group 3); hCG on Day 5 following PMSG on Day 1 caused ovulation (Group 4). Although AT did not block the action of PMSG and hCG at the ovary, AT did block the mechanisms by which estrogen triggers the preovulatory LH surge and estrus.     

Reduction of testicular luteinizing hormone/human chorionic gonadotropin receptors by [D-Trp6]-luteinizing hormone releasing hormone in hypophysectomized rats.

Adult and immature male rats were hypophysectomized and injected daily with saline or 0.2 or 2 μg of superactive Luteinizing Hormone Releasing Hormone (LHRH) agonist, [D-Trp⁶]-LHRH subcutaneously for seven days - with, or without, concomitant treatment of 1 IU Human Chorionic Gonadotropin (hCG) or 50 IU Pregnant Mare Serum. The administration of [D-Trp⁶]-LHRH reduced Luteinizing Hormone/Human Chorionic Gonadotropin receptors in all cases. The magnitude of this reduction was dose-related. As small a dose as 0.2 μg of the peptide resulted in approximately a 72% reduction of the receptors. The results suggest a direct action of [D-Trp⁶]-LHRH on the testis. It also indicated that reduction of testicular Luteinizing Hormone/Human Chorionic Gonadotropin receptors by the peptide is not necessarily due to the over-stimulation of Luteinizing Hormone (LH) release from the pituitary through a “down regulation” mechanism.     

Effect of periovulatory prostaglandin F2alpha on pregnancy rates and luteal function in the mare.

The objective of this study was to determine whether periovulatory treatments with PGF2alpha affects the development of the CL, and whether the treatment was detrimental to the establishment of pregnancy. Reproductively sound mares were assigned randomly to one of the following treatment groups during consecutive estrus cycles: 1. 3,000 IU hCG within 24 hours before artificial insemination and 500 microg cloprostenol (PGF2alpha analogue) on Days 0, 1, and 2 after ovulation (n=8), 2. 2 mL sterile water injection within 24 hours before artificial insemination and 500 microg cloprostenol on Days 0, 1, and 2 after ovulation (n=8); 3. 3,000 IU hCG within 24 hours before artificial insemination and 500 microg cloprostenol on Day 2 after ovulation (n=8); or 4. 3,000 IU hCG within 24 hours before artificial insemination and 2 mL of sterile water on Days 0, 1, and 2 after ovulation (controls; n=8). Blood samples were collected from the jugular vein on Days 0, 1, 2, 5, 8, 11, and 14 after ovulation. Plasma progesterone concentrations were determined by the use of a solid phase 125I radioimmunoassay. All mares were examined for pregnancy by the use of transrectal ultrasonography at 14 days after ovulation. Mares in Group 1 and 2 had lower plasma progesterone concentrations at Day 2 and 5, compared to mares in the control group (P < 0.001). No difference was detected between group 1 and 2. Plasma progesterone concentrations in group 3 were similar to the control group until the day of treatment, but decreased after treatment and were significantly lower than the control group at Day 5 (P < 0.001). Plasma progesterone concentrations increased in all treatment groups after Day 5, and were comparable among all groups at Day 14 after ovulation. Cloprostenol treatment had a significant effect on pregnancy rates (P < 0.01). The pregnancy rate was 12.5% in Group 1, 25% in Group 2, 38% in Group 3, and 62.5% in Group 4. It was concluded that periovulatory treatment with PGF2alpha has a detrimental effect on early luteal function and pregnancy.     

Effects of dibutyryl cAMP, LHRH, and aromatase inhibitor on simultaneous outputs of prostaglandin F2 alpha, and 13,14-dihydro-15-keto-prostaglandin F2 alpha by term placental explants

Explants from term human placentas were maintained in culture with daily changes of medium. Daily output of PGF2 alpha and PGFM1 decreased during the course of the incubation. Addition of 4 micrograms/ml DHEAS or 67 micrograms/ml LDL cholesterol had no effect on output of PGF2 alpha or PGFM. Addition of 1.6, 3.2, or 6.4 micrograms/ml of LHRH to the culture plates had no effect on output of PGFM or PGF2 alpha, but LHRH increased hCG output. Dibutyryl cAMP (1mM, 2mM, and 4 mM) increased output of PGF2 alpha, PGFM, and hCG. Aromatase inhibitor decreased hCG output, but it was without effect on output of PGF2 alpha, or PGFM, Significant correlations were demonstrated between progesterone, PGFM, PGF2 alpha, and hCG, suggesting that PGF2 alpha originates in the syncytiotrophoblast cell. The ability of LHRH to stimulate output of hCG but not PGF2 alpha while dbcAMP stimulated both suggests that either PGF2 alpha and hCG arise in different cells or that LHRH does not act through cAMP.     

Ovarian function in Nelore (Bos taurus indicus) cows after post-ovulation hormonal treatments

Maternal recognition of pregnancy in the cow requires successful signaling by the conceptus to block luteolysis. Conceptus growth and function depend on an optimal uterine environment, regulated by luteal progesterone. The objective of this study was to test strategies to optimize luteal function, as well as prevent a dominant follicle from initiating luteolysis. Nelore (Bos taurus indicus) beef cows (n=40) were submitted to a GnRH/PGF(2alpha)/GnRH protocol. Cows that ovulated from a dominant ovarian follicle (ovulation=Day 0) were allocated to receive: no additional treatment (G(C); n=7); 3000IU of hCG on Day 5 (G(hCG); n=5); 5mg of estradiol-17beta on Day 12 (G(E2); n=6); or 3000IU of hCG on Day 5 and 5mg of estradiol-17beta on Day 12 (G(hCG/E2); n=5). Ultrasonographic imaging of the ovaries, assessment of plasma progesterone concentration, and detection of estrus were done daily from Day 5 to the day of subsequent ovulation. Treatment with hCG induced an accessory CL, increased CL volume, and plasma progesterone concentration throughout the luteal phase (P<0.01). Estradiol-17beta induced atresia and recruitment of a new wave of follicular growth; it eliminated a potentially estrogen-active, growing ovarian follicle within the critical period for maternal recognition of pregnancy, but it also hastened luteolysis (Days 16 or 17 vs. Days 18 or 19 in non-treated cows). In conclusion, the approaches tested enhanced luteal function (hCG) and altered ovarian follicular dynamics (estradiol-17beta), but were unable to extend the life-span of the CL in Nelore cows.