Effect Of Human Chorionic Gonadotropin Research Articles

The effect of human chorionic gonadotrophin on the expression of progesterone receptors in human luteal cells in vivo and in vitro

The human corpus luteum expresses genomic progesterone receptors (PRs) suggesting that progesterone may have an autocrine or paracrine role in luteal function. We hypothesised that the reduction in luteal PR reported in the late-luteal phase augmented progesterone withdrawal and had a role in luteolysis. We therefore tested the hypothesis that luteal rescue with human chorionic gonadotrophin (hCG) would maintain PR expression. PR was immunolocalised to different cell types in human corpora lutea (n = 35) from different stages of the luteal phase and after luteal rescue with exogenous hCG. There was no change in the staining intensity of theca-lutein cell or stromal cell PR throughout the luteal phase or after luteal rescue. In the late-luteal phase, granulosa-lutein cell PR immunostaining was reduced (P < 0.05) but the trend to reduction was also seen after luteal rescue with hCG (P = 0.055). To further investigate the effect of hCG on granulosa-lutein cell PR expression, an in vitro model system of cultured human luteinised granulosa cells was studied. Cells were cultured for 12-13 days exposed to different patterns of hCG and aminoglutethamide to manipulate progesterone secretion (P < 0.0001). Expression of PR A/B and PR B isoforms was examined by quantitative real-time RT-PCR. PR A/B mRNA was lower (P < 0.05) after 11-13 days of culture than after 7 days of culture. This reduction could not be prevented by hCG in the presence (P < 0.05) or absence (P < 0.05) of stimulated progesterone secretion. The expression of PR B mRNA showed a similar pattern (P = 0.054). Simulated early pregnancy in vivo and hCG treatment of luteinised granulosa cells in vitro did not appear to prevent the down-regulation of PR seen during luteolysis.

391Are the effects of human chorionic gonadotropin on normal testicular tissue in rats dose-dependent and reversible?

391Are the effects of human chorionic gonadotropin on normal testicular tissue in rats dose-dependent and reversible?

Adenosine Triphosphate Induces Activation of Caspase-3 in Apoptosis of Human Granulosa-luteal Cells

Adenosine triphosphate (ATP) has been shown to induce programmed cell death in various systems. However, little is known about the effect of ATP on human granulosa-luteal cells (hGLCs). The present study was designed to examine the effect of ATP on the activation of the caspase signaling pathway and its role in inducing programmed cell death. Human GLCs were collected from patients undergoing in vitro fertilization programs, and then were cultured in FBS-supplemented DMEM for 3 days prior to our studies. To examine the dose-response relationship, hGLCs were treated with increasing concentrations of ATP (10 microM, 100 microM, 1 mM or 10 mM) for 24 hours. For time-course experiments, hGLCs were treated with 10 mM ATP for 6, 12, or 24 hours. Western blot analysis was performed using antibodies against the pro- and active forms of caspase-3, -9, or PARP. To quantify the induction of apoptosis, DNA fragmentation was measured using the cell death detection enzyme-linked immunosorbent assay. To examine the effect of human chorionic gonadotropin (hCG) in protecting cells from apoptosis, hGLCs were treated with 10 IU hCG in the presence of 10 mM ATP for 12 hours. It was demonstrated that ATP was capable of inducing DNA fragmentation in a dose- and time-dependent manner. Furthermore, Western blot analysis, which detected the pro- and active forms of caspase-3, or PARP, demonstrated that ATP activated the caspase-signaling pathway, leading to the proteolytic conversion of pro-caspase-3 to active caspase-3, and the subsequent cleavage of the caspase substrate PARP. Based on our observation, caspase-9 was not triggered by ATP. Interestingly, hCG attenuated the effect of ATP in activating the caspase signaling pathway. To our knowledge, this is the first demonstration of the ATP-induced activation of the caspase signaling pathway in the human ovary. These results support the notion that the caspase-signaling pathway is involved in mediating ATP actions in the human ovary.

Systemic HCG treatment in patients with endometriosis: A new perspective for a painful disease

Endometriosis is characterized by the presence of endometrium-like tissue outside the uterus. This condition causes painful periods, chronic pelvic pain, subfertility and a profound reduction in quality of life, especially during women's reproductive years. Currently available medical therapies offer comparatively little therapeutic benefit and are often burdened by considerable side effects. However, since clinical evidence shows that pregnancy leads to alleviation of endometriotic symptoms, we have for the first time examined the effect of human chorionic gonadotrophin (HCG) injections on symptoms such as dysmenorrhea and pelvic pain. Thirty-one patients with histologically verified endometriosis refractory to therapy received 1 to 2 intramuscular injections of 1500 to 5000 IU HCG per week for a period of 3-12 months. A QoL questionnaire and the visual analog pain intensity scale (VAS) were used to evaluate quality of life and pain intensity, respectively, before and after three months of treatment. Three months of HCG therapy led to a highly significant reduction of endometriosis-related pain (p<0.001, Wilcoxon test) and to improvement of disease-related parameters such as sleeplessness (p<0.001), irritability (p<0.001), overall discomfort (p<0.001), depressive moods (p<0.001) and painful defecation (p=0.01). Dyspareunia and dysmenorrhea also clearly improved (both p<0.001), though HCG did not lead to significant reduction of dysuria (p=0.66). Prolonged therapy with HCG for up to 12 months (mean: 4.42 months) did not lead to reduction of the beneficial effect. HCG injections lead to significant and clinically relevant reduction in pain intensity and to greatly improved quality of life in women with therapy-refractory endometriosis. The remarkable clinical effect of parenteral HCG in our study will have to be confirmed in additional trials but clearly indicates an extremely promising new perspective in the treatment of endometriosis.

Two types of calcium channels in human ovarian endocrine cells: involvement in steroidogenesis.

Nature, regulation, and functional role of ion channels of human ovarian endocrine cells are not well known. In our present study, we show two types of voltage-activated Ca(2+) currents (I(Ca)) in cultured human luteinized granulosa cells (GCs), as assessed by whole-cell patch-clamp experiments. Electrophysiological properties, namely low threshold of activation, pronounced time-dependent inactivation, slow and voltage-dependent deactivation kinetics, insensitivity to SNX-482, and high sensitivity to Ni(2+), defined the predominant I(Ca) as a T-type Ca(2+) current (I(Ca.T)). In 4% of cells a Ni(2+)-insensitive I(Ca) was measured alone or together with I(Ca.T). This Ca(2+) current was high voltage activated and highly sensitive to dihydropyridine, indicative of an L-type Ca(2+) current. RT-PCR analysis demonstrated the presence of mRNA coding for alpha(1)-subunits of two different Ca(2+) channels (T-type Ca(v)3.2 and L-type Ca(v)1.2) in GCs. In addition, these two types were detected in the human corpus luteum by RT-PCR (Ca(v)3.2) and immunohistochemistry (Ca(v)1.2). Although stimulation of cultured GCs with human chorionic gonadotropin did not change the characteristics of recorded I(Ca.T), it markedly increased the percentage of cells displaying I(Ca) from 29 to 63% and significantly increased (2.2-fold) the density of I(Ca.T). Furthermore, the stimulatory effect of human chorionic gonadotropin on progesterone production was diminished by pharmacological blockage of I(Ca.T) by Ni(2+) or flunarizine. Thus, our study provides evidence that human GCs in vivo and in vitro express T- and L-type Ca(2+) channels and that the Ca(v)3.2 (also called alpha(1H)) isoform is involved in a fundamental endocrine function of these cells.

Low temperature blocks the stimulatory effect of human chorionic gonadotropin on steroidogenic acute regulatory protein mRNA and testosterone production but not cyclic adenosine monophosphate in mouse Leydig tumor cells

Low temperatures slow down metabolism, partly because the kinetic energy of molecules is reduced and enzymes may be structurally impaired. We now report that relative to its maximal activity at 37°C, adenylate cyclase (AC) still retained 25% functionality (determined as cyclic adenosine monophosphate [cAMP] production) at 4°C in mouse Leydig tumor cells (MLTC-1) in response to 50 IU/L human chorionic gonadotropin (hCG), whereas steroidogenic acute regulatory (StAR) protein mRNA and testosterone production were completely impaired. The incubation of MLTC-1 with the phosphodiesterase inhibitor (3-isobutyl-1-methylxanthine; IBMX) resulted in significantly increased intracellular cAMP concentration at all 3 temperatures, but this had no impact on testosterone production. AC, cAMP, and phosphodiesterase form an important intracellular second-messenger mechanism in many organisms, some that inhabit very low temperature niches. The cold-resistance of AC and phosphodiesterase may thus have evolved to cope with adverse conditions. Although hibernation may lead to decreased steroid hormone production, it is also likely that cold-mediated decreased steroid hormone production induces hibernation.

Physiological and pathological aspects of the effect of human chorionic gonadotropin on the thyroid

Physiological and pathological aspects of the effect of human chorionic gonadotropin on the thyroid

Physiological and pathological aspects of the effect of human chorionic gonadotropin on the thyroid.

Human chorionic gonadotropin (hCG) is a glycoprotein hormone that has structural similarity to TSH. At the time of the peak hCG levels in normal pregnancy, serum TSH levels fall and bear a mirror image to the hCG peak. This reduction in TSH suggests that hCG causes an increased secretion of T4 and T3. Women with hyperemisis gravidarum often have high hCG levels that cause transient hyperthyroidsm. In the vast majority of such patients, there will be spontaneous remission of the increased thyroid function when the vomiting stops in several weeks. When there are clinical features of hyperthyroidism, it is be reasonable to treat with antithyroid drugs or a beta-adrenergic blocker, but treatment is rarely required beyond 22 weeks of gestation. Hyperthyroidism or increased thyroid function has been reported in many patients with trophoblastic tumors, either hydatiditform mole or choriocarcinoma. The diagnosis of hydatidiform mole is made by ultrasonography that shows a 'snowstorm' appearance without a fetus. Hydatidiform moles secrete large amounts of hCG proportional to the mass of the tumor. The development of hyperthyroidism requires hCG levels of >200 U/ml that are sustained for several weeks. Removal of the mole cures the hyperthyroidism. There have been many case reports of hyperthyroidism in women with choriocarcinoma and high hCG levels. The principal therapy is chemotherapy, usually given at a specialized center. With effective chemotherapy, long-term survival exceeds 95%. A unique family with recurrent gestational hyperthyroidism associated with hyperemesis gravidarum was found to have a mutation in the extracellular domain of the TSH receptor that made it responsive to normal levels of hCG.

Effect of human chorionic gonadotropin in the gene expression profile of MCF-7 cells

The preventive effect of human chorionic gonadotropin (hCG)-induced differentiation on experimental mammary carcinogenesis has been reported to be due to the inhibition of cell proliferation, increased DNA repair capabilities of the mammary epithelium, decreased binding of the carcinogen to the DNA and activation of programmed cell death genes leading to apoptosis. To further our understanding of the molecular pathway of the hCG action on mammary epithelial cells we have analyzed gene expression profiles of MCF-7 cells treated with hCG for 24, 48, and 96 h, using a DNA microarray consisting of 1176 genes. Comparison of expression between the treated and not treated cells enabled us to identify 48 genes that are affected by this hormone. Importantly, there is a cluster of genes that are overexpressed during the first 24 h and level off thereafter, whereas other genes are maximally expressed at 96 h of treatment. The results obtained in this study demonstrated that genes regulating cell proliferation, apoptosis, cell trafficking, and DNA repair are significantly affected by hCG in human breast cancer cells in vitro.

Gonadotropin-mediated regulation of the murine VEGF expression in MA-10 Leydig cells.

Presence of vascular endothelial growth factor (VEGF) is not only limited to cells directly involved in angiogenesis but has also been demonstrated in steroidogenic cells like testicular Leydig cells. Because Leydig cells are subjected to regulation by gonadotropic hormones and produce steroid hormones, we have investigated here the effects of human chorionic gonadotropin (hCG) or steroid hormones on VEGF expression in cultured mouse tumor Leydig cells (MA-10 cells) and have then analyzed the underlying molecular mechanisms. Northern blot analysis and enzyme-linked immunosorbent assays revealed increases in VEGF mRNA and protein levels, respectively, over 3-20 hours in MA-10 cells after stimulation with hCG or 8-Br-cAMP. Although MA-10 cells lack the classical progesterone receptor, progesterone was able to stimulate VEGF expression. Promoter analyses and antibody supershift experiments suggested that the proximal region is able to constitutively bind the transcription factors Sp1 and Sp3. Mutations of 2 potential Sp1 binding sites in the proximal region showed the requirement of these motifs for stimulation of VEGF by hCG and 8-Br-cAMP. The distal cytosine-rich sequence interacts with so far-unidentified faster migrating factors. Following stimulation with hCG or 8-Br-cAMP, the binding of these proteins was increased in the complexes formed in the proximal and distal regions. VEGF expression in Leydig cells is regulated by gonadotropin via a cAMP-dependent mechanism, and the transcription factors Sp1 and Sp3 appear to be involved in the activation of the promoter. Progesterone also appears to play a role in the regulation of VEGF, acting presumably via a nonconventional receptor that remains to be characterized yet.

Effect of human chorionic gonadotropin on luteal luteinizing hormone concentrations in natural cycles

Effect of human chorionic gonadotropin on luteal luteinizing hormone concentrations in natural cycles

Human chorionic gonadotrophin relaxation of human pregnant myometrium and activation of the BKCa channel.

The uterorelaxant effect of human chorionic gonadotropin (hCG) is regarded as an important mediator in maintenance of uterine quiescence during pregnancy with clinical potential for tocolysis, the mechanisms of which are unknown. The large conductance calcium-activated K(+) channel (BK(Ca)) is ubiquitously encountered in human uterine tissue and plays a significant role in modulating myometrial cell membrane potential and excitability. The objective of this study was to investigate the involvement of BK(Ca) channel function in the response of human myometrial cells to hCG. Single electrophysiological BK(Ca) channel recordings from freshly dispersed myocytes were obtained in the presence and absence of increasing hCG concentrations. Isometric tension studies, investigating the effects of hCG on isolated myometrial contractions, in the presence and absence of the BK(Ca) channel blocker, iberiotoxin, were performed. The hCG significantly increased the open-state probability of these channels in a concentration-dependent manner [control 0.036 +/- 0.01; 1 IU/ml hCG 0.065 +/- 0.014 (P = 0.262); 10 IU/ml hCG 0.111 +/- 0.009 (P = 0.001); and 100 IU/ml hCG 0.098 +/- 0.004 (P = 0.007)]. In vitro functional studies demonstrated that hCG exerted a significant concentration-dependent relaxant effect on human myometrial tissue. This effect was significantly attenuated by preincubation with iberiotoxin (P < 0.05). These findings outline that activation of BK(Ca) channel activity may explain the potent uterorelaxant effect of hCG.

Analyses of dendritic cell subsets in pregnancy.

Changes in the frequency of dendritic cell (DC) subsets in the peripheral blood were analyzed as pregnancy progressed, and the effects of human chorionic gonadotropin (hCG) on myeloid and lymphoid DC subsets were phenotypically and functionally examined. Two major subsets of DCs were prepared from the peripheral blood by flow cytometry. Major histocompatibility complex class II molecules and adhesion/costimulatory molecules were examined before and after culture with hCG. hCG receptors on both DC subsets were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR). The frequency of myeloid DCs increased in the late stage of pregnancy, while that of lymphoid DCs gradually decreased. The addition of hCG (physiological concentrations in pregnancy) to cultures induced the maturation of both DC subsets in conjunction with increases in the expression of adhesion/costimulatory molecules, their stimulatory activities in allogeneic mixed lymphocyte/leukocyte reaction, and cytokine secretion (interleukin-12 and interferon-gamma). hCG receptors were found in both DC subsets by RT-PCR, suggesting that these stimulatory activities of hCG are mediated by hCG receptors on the DCs. hCG can modulate immune responses through the activation of myeloid and lymphoid DCs.

Human chorionic gonadotropin (HCG) activates monocytes to produce interleukin-8 via a different pathway from luteinizing hormone/HCG receptor system.

To investigate immune-endocrine interactions between the embryo and the mother early in pregnancy, we examined the effects of human chorionic gonadotropin (HCG) on IL-8 production by peripheral blood mononuclear cells (PBMC). Recombinant HCG promoted IL-8 secretion by PBMC derived from nonpregnant women. The induction of IL-8 mRNA expression was observed after 30 min of HCG stimulation. Adsorption of the HCG with anti-HCG antibodies confirmed the specificity of this effect. The translocation of nuclear factor kappaB into the nucleus and subsequent IL-8 production were observed mainly in monocytes, and IL-8 production was reduced when a proteasome inhibitor was added to inactivate nuclear factor kappaB. Although fluorescein isothiocyanate-labeled HCG was bound to the majority of monocytes, cell surface expression of HCG receptor was hardly detected. IL-8 production by HCG was not affected by inhibitors of protein kinases A and C. In contrast, this stimulation was attenuated by D-mannose, which inhibits binding to C-type lectins. The basal IL-8 production by PBMC from women early in pregnancy was significantly elevated, compared with that from nonpregnant women. This study showed that human monocytes respond to HCG and secrete IL-8 through a pathway different from the HCG receptor system, suggesting that this glycoprotein hormone can react with not only endocrine cells but also immune cells early in pregnancy, probably via primitive systems such as C-type lectins.

Human chorionic gonadotrophin reduces matrix metalloproteinases expression in JEG-3 choriocarcinoma cell line

Objective To uncover the effect of human chorionic gonadotrophin (hCG) on the invasion of choriocarcinoma cells.Methods The effect of hCG on the expression of matrix metalloproteinases (MMPs) in JEG\|3 choriocarcinoma cell line was investigated by applying the method of reverse transcription polymerase chain reaction (RT\|PCR). Results The results showed that, among the 18 types of MMPs only MMP\|8,\|10, \|12,\|19 were found to be expressed by JEG\|3 cells. After the incubation with 25 IU/ml hCG for 50hours, the expression of these 4 types of MMPs were all significantly reduced. Conclusion The invasiveness of JEG\|3 choriocarcinoma cell line was associated with the expression of MMP\|8, \|10, \|12, \|19, high levels of hCG could reduce the invasion of choriocarcinoma cells by inhibiting MMPs expression.

Effects of a GnRH antagonist inhibition of luteinizing hormone during the preovulatory period in the mare

The objective of Experiment 1 was to determine a dose and frequency of gonadotropin-releasing hormone (GnRH) antagonist administration to effectively suppress serum luteinizing hormone (LH) concentration and to delay ovulation when administered to mares. The objectives of Experiment 2 were 1) to determine the effects of subcutaneous or intravenous administration of a GnRH antagonist or oral altrenogest on serum LH concentration in the estrual mare; and 2) to determine the effectiveness of human chorionic gonadotropin (hCG) in inducing ovulation in mares with suppressed LH concentrations. In Experiment 1, mares (N = 20) were randomly assigned and treated with either 5% mannitol (control, single subcutaneous injection, 1 mL, at time 0; n = 5); low-dose GnRH antagonist (single subcutaneous injection, 0.01 mg/kg, at time 0; n = 5); frequent low-dose GnRH antagonist (subcutaneous injections, 0.01 mg/kg, at 0, 6, 18, and 24 hours; n = 5); or high-dose GnRH antagonist (single subcutaneous injection, 0.04 mg/kg, at time 0; n = 5). Both the frequent low-dose and high-dose GnRH antagonist treatments resulted in significantly lower LH concentrations compared with controls at 90, 102, and 114 hours after treatment (P < .05). In Experiment 2, mares (N = 38) were randomly assigned and treated with subcutaneous sterile saline (control), altrenogest (oral), subcutaneous GnRH antagonist, or intravenous GnRH antagonist. LH concentration for the altrenogest group was lower than the control group at 3, 4, 18, and 30 hours after treatment (P < .05). LH concentration for both the subcutaneous and intravenous GnRH antagonist groups were lower compared with the control group at several time points (P < .05). Based on these data, dose but not frequency of administration of a GnRH antagonist lowered LH concentration in the estrous mare but did not delay ovulation. In addition, serum LH concentrations can be lowered and ovulation effectively postponed in mares treated with altrenogest followed by administration of hCG. This indicates that serum LH concentrations can be lowered and ovulation effectively postponed in mares treated with altrenogest followed by administration of hCG.

Inhibitory Effects of Human Chorionic Gonadotropin (hCG) Preparations on HIV Infection of Human Placenta in vitro

Human chorionic gonadotropin (hCG) has been implicated in modifying Kaposi sarcoma lesions in HIV positive patients and in reducing HIV infection in human lymphocytes and human choriocarcinoma cells. These anti-HIV effects of hCG may contribute to the limited maternal to fetal transmission of HIV infection (25–35 per cent without treatment). However, it is unknown whether such high dosages of hCG have any effect on vertical transmission of HIV or on the infection of the human placenta with cell-free HIV. We have investigated in a dose dependent manner the effects of hCG on HIV-1 infection of human term placentae.Using commercially available hCG preparations, the ability to modify the infection of placental explants in vitro was examined. Sigma hCG and ICN β-hCG (0.1, 1, 10IU/ml) and APL hCG and Sigma and Serono recombinant hCG (0.1, 1, 10, 100IU/ml) were added during 6h of pre-incubation and the 4 days of culture (3 days following the 24h exposure to HIV-1 Ba-L strain). Cell-free HIV infection of the placental explants was documented using DNA-PCR detection of Gag and LTR regions of HIV. Each experimental condition was repeated in different placentae (n=5) and each PCR amplification was performed in duplicate with each primer set (total=20).Our results demonstrate that there is a dose dependent inhibition of HIV-1 infection in the human placenta above the physiologic levels (0.2IU/ml) of hCG produced during incubation. At the highest concentration used (100IU/ml), 80 per cent inhibition of HIV infection was achieved with urinary extract hCG and about 50 per cent with recombinant hCG. β-hCG alone appears to possess an efficacy equivalent to the complete hCG molecule.In this in vitro study, hCG demonstrates specific anti-HIV inhibitory properties that cannot be solely attributed to urinary contamination of the commercial preparations. Such inhibitory action of hCG may be present at varying levels throughout gestation based upon the circulating levels of hCG and its production by the placenta. Knowledge of the specific mechanisms underlying this inhibition is necessary before clinical applications can be considered.

Human chorionic gonadotrophin inhibition of pregnant human myometrial contractility

Objective To evaluate the effect of human chorionic gonadotrophin (hCG) on pregnant human myometrial contractility in vitro and to determine whether the hCG-elicited effect was oestrogen dependant. Methods Isometric tension recording was performed under physiological conditions in isolated myometrial strips from biopsies obtained at elective caesarean section. The effect of cumulative additions of hCG (0.001, 0.01, 0.1, 1.0 and 10 iu/mL) on myometrial contractility was evaluated. Secondarily, the contractile activity of pregnant myometrium following hCG exposure was investigated in tissue pre-treated with beta-oestradiol. Results hCG exerted a statistically significant relaxant effect on pregnant human myometrial tissue. The relaxant effect increased with increasing concentrations of hCG from 8.96% (SEM 2.06) (0.001 iu/mL hCG; P<0.01) to a net cumulative total of 58.50% (SEM 3.74) (10 iu/mL hCG; P<0.01). The relaxant effect was also time-dependant, increasing in magnitude throughout the duration of experiments. Beta-oestradiol did not significantly affect the response of myometrial tissue to hCG. Conclusions These results clearly demonstrate that hCG exerts a significant concentration-dependant relaxant effect on human myometrial tissue obtained rate in pregnancy. These findings outline an inhibitory physiological role of hCG on human myometrial contractility and raise the possibility of its potential use as a tocolytic.

Distinct regulation of gene expression by prostaglandin F(2alpha) (PGF(2alpha)) is associated with PGF(2alpha) resistance or susceptibility in human granulosa-luteal cells.

The effects of human chorionic gonadotrophin (HCG) and prostaglandin F(2alpha) (PGF(2alpha)) on regulation of human granulosa-luteal cell (GLC) function at different stages of differentiation (day 2 versus day 8 of culture) were studied. Expression of LH receptor mRNA and biosynthesis of progesterone were HCG dependent in human GLC at all stages (n = 6, P < 0.05). Steady-state concentrations of mRNA encoding for FP (a specific high-affinity plasma membrane receptor for PGF(2alpha)) were not dependent on, but were stimulated by, addition of HCG (10 IU/ml) or 8-bromo-cAMP (0.5 mmol/l) (n = 6, P < 0.05). Treatment with PGF(2alpha) (100 nmol/l) decreased FP mRNA concentration, but had no effect on LH receptor and cyclo oxygenase-2 (COX-2) expression on day 2 of cultured GLC (n = 8). As a result, the progesterone biosynthesis by GLC was not affected. On day 8, PGF(2alpha) induced FP and PGHS-2 expression and at the same time decreased LH receptor expression, resulting in inhibition of progesterone output by GLC. Our data demonstrated that early stage GLC (day 2 of culture) are resistant to PGF(2alpha)-induced inhibition of progesterone synthesis but underwent further differentiation and acquired luteolytic capacity after 8 days culture in vitro. We conclude that, via distinct gene regulation at different stages of differentiation, human GLC may become resistant or susceptible to PGF(2alpha)-induced luteolysis.

The Effect of Human Chorionic Gonadotropin on the Development and Function of Bovine Corpus Luteum.

Proceeding with research into human chorionic gonadotropin (hCG) administration, designed to promote pregnancy rates in embryo transfer, hCG was administered to bovine recipients on the day of ovulation in Holstein cows and the day of selection of recipients, ie., day prior to embryo transfer (5 days after the day of ovulation), and the changes in ovaries and the concentrations of plasma progesterone (P) and estradiol-17β (E2) levels after administration were determined. Changes in the ovaries and functions of blood P and E2 levels after administration were determined in order to investigate the effects of hCG on increase in luteinization and functions of P secretion. Nine Holstein dairy cows were divided into two groups. All 4 cows of one group received an intramuscular injection of saline at a dose of 5 ml on the day of ovulation (Day 0-control group: the day of ovulation was designated as Day 0), which was followed by an injection of hCG at a dose of 1,500 IU on the corresponding day of the next estrous cycle (Day 0-hCG group). In a similar way, 4 cows in the other group received an injection of saline at a dose of 5 ml on day 5 (Day 5-control group), then 3 of the 4 cows and the remaining cow received intramuscular injections of hCG at a dose of 1,500 IU on the corresponding day of the next estrous cycle (Day 5-hCG group). These cattle were examined for changes in ovarian follicles and corpus luteum (CL) every day or every other day by rectal palpation and ultrasonography, and blood samples were collected every day for the P and E2 analysis. The estrous cycle lengths in the hCG groups tended to be slightly longer than those in the control group, though the difference was not significant. In the Day 5-hCG group, ovulation was induced in all cows 1 or 2 days after hCG administration, and was followed by the development of new CL (induced CL). Ultrasonographic observations revealed that the total luteal tissue area of the CL periodicum and the induced CL in the Day 5-hCG group were significantly (P<0.05) wider than those in the Day 5- control group from 3 days after hCG administration onward. Plasma P levels started rising 3 hours after hCG administration in the Day 5-hCG group, and they were significantly (P<0.05) higher than those in the Day 5-control group on days 6, 7, 12, 13 and 14, respectively. Plasma E2 levels decreased rapidly after hCG administration in the Day 5-hCG group, and were lower than those in the Day 5-control group. These results showed enhancement of the luteal activity and a decrease in plasma E2 level by hCG administration 5 days after ovulation, suggesting that the hCG treatment on the day prior to embryo transfer is effective at increasing the pregnancy rate in embryo transfer.