Pregnancy recognition signaling mechanisms in ruminants and pigs

Maternal recognition of pregnancy refers to the requirement for the conceptus (embryo and its associated extra-embryonic membranes) to produce a hormone that acts on the uterus and/or corpus luteum (CL) to ensure maintenance of a functional CL for production of progesterone; the hormone required for pregnancy in most mammals. The pregnancy recognition signal in primates is chorionic gonadotrophin which acts directly on the CL via luteinizing hormone receptors to ensure maintenance of functional CL during pregnancy. In ruminants, interferon tau (IFNT) is the pregnancy recognition signal. IFNT is secreted during the peri-implantation period of pregnancy and acts on uterine epithelia to silence expression of estrogen receptor alpha and oxytocin receptor which abrogates the oxytocin-dependent release of luteolytic pulses of prostaglandin F2-alpha (PGF) by uterine epithelia; therefore, the CL continues to produce progesterone required for pregnancy. Pig conceptuses secrete interferon delta and interferon gamma during the peri-implantation period of pregnancy, but there is no evidence that they are involved in pregnancy recognition signaling. Rather, pig conceptuses secrete abundant amounts of estrogens between Days 11 to 15 of pregnancy required for maternal recognition of pregnancy. Estrogen, likely in concert with prolactin, prevents secretion of PGF into the uterine venous drainage (endocrine secretion), but maintains secretion of PGF into the uterine lumen (exocrine secretion) where it is metabolized to a form that is not luteolytic. Since PGF is sequestered within the uterine lumen and unavailable to induce luteolysis, functional CL are maintained for production of progesterone. In addition to effects of chorionic gonadotrophin, IFNT and estrogens to signal pregnancy recognition, these hormones act on uterine epithelia to enhance expression of genes critical for growth and development of the conceptus.     

Role and mechanism of endothelial hydrogen sulfide in anti-atherosclerosis effect of estrogen

AIM：To investigate possible role and mechanism of endothelial hydrogen sulfide (H2S) in the anti-atherosclerosis effect of estrogen. METHODS：For in vitro experiment, cultured human umbilical vein endothelial cells (HUVECs) were treated with 17β-estradiol (E2), estrogen receptor α (ERα) agonist propylpyrazole triol (PPT), estrogen receptor β (ERβ) agonist diarylpropionitrile (DPN) and estrogen receptor antagonist ICI 182780 (ICI) for 5 min, and then the concentration of H2S in cell culture supernatants was detected by sensitive sulphur electrode assay. For in vivo experiment, high-fat diet-fed and ovariectomized (OVX) female ApoE–/– C57BL/6 mice were randomly divided into 3 groups and treated with placebo (OVX group), E2 (OVX+E2 group) and E2 plus cystathionine γ-lyase (CSE) inhibitor DL-propargylglycine (PPG) (OVX+E2+PPG group), respectively, and the blood concentration of H2S and the atherosclerotic plaque size were detected 8 weeks later. RESULTS：E2 significantly enhanced the release of H2S from HUVECs in a concentration-and time-dependant manner which could be blocked by the administration of ICI. Meanwhile, ERα agonist PPT, not ERβ agonist DPN, demonstrated similar effects to E2. Compared with OVX group, the atherosclerosis in mice was attenuated and the blood concentration of H2S was elevated in OVX+E2 group, while no significant changes were detected in OVX+E2+PPG group. CONCLUSION: Endothelial H2S can be rapidly released when membrane ERα is activated by estrogen, which plays a very important role in the anti-atherosclerosis effect of estrogen.     

电针肾旁穴对兔下丘脑雌激素受体免疫反应阳性产物的影响

研究电针肾旁穴对下丘脑内雌激素受体免疫反应阳性产物的影响及对生殖内分泌的调控。采用电针穴位法及免疫组织化学SP法。电针组兔下丘脑的视上核、室旁核、视交叉上核、室周核、腹内侧核、背侧区、小细胞核等核区有大量阳性神经元出现，染色深，突起明显，细胞形态多样，轮廓清晰；而正常组相应神经核团中阳性细胞数量较少且淡染，突起也不明显，形态单一或轮廓不清。电针肾旁穴可使家兔上述核团内雌激素受体的表达增强，从而对生殖内分泌活动进行调控。     

大鼠不同时期乳腺组织及血液中雌激素变化规律

研究大鼠不同时期乳腺及血液中雌激素变化规律。选择雌性SD大鼠42只,分别为处女期、妊娠前、中、后期,每期间隔6d,泌乳期前、中、后期,每期间隔6d,每期6只。规定时间取各期大鼠乳腺组织及血清。通过放免测各个时期雌激素含量并进行分析。结果表明大鼠血清E2水平中处女期最高,妊娠开始呈现先降后升趋势,而泌乳各时期呈逐渐下降趋势。处女期与其它时期差异显著(P<0.05),整个妊娠期以妊娠后期最高,且差异不显著(P>0.05);泌乳前、中、后期明显高于妊娠期水平(P<0.05);乳腺E2:泌乳前期最高,然后呈现下降趋势,处女期与各期差异显著(P<0.05),泌乳前期明显高于其它时期(P<0.05),而显著高于妊娠中期和后期(P<0.05)。雌激素在维持乳腺发育及启动和维持泌乳方面发挥着重要作用。     

雌激素受体碘标记放射配体的合成与选择

雌激素的放射受体分析在药物设计、癌症等疾病的诊断和治疗等方面的应用十分广泛。本研究中,共合成了7种125I标记雌激素放射配体,分别为125I-Estradiol-6-CMO-His1、25I-Estradiol-3-CME-His1、25I-Estradiol-17-HS-His、21-25I-Estradiol、41-25I-Estradiol、2,4-2125I-Estradiol和16α125I-Estradiol,并比较了它们用于放射受体分析(RRA)的结果,表明在上述雌激素放射配体中,16α125I-Estradiol具有较好的生物活性。     

Central estrogen action sites involved in prepubertal restraint of pulsatile luteinizing hormone release in female rats

The present study aimed to determine estrogen feedback action sites to mediate prepubertal restraint of gonadotropin-releasing hormone (GnRH)/luteinizing hormone (LH) release in female rats. Wistar-Imamichi strain rats were ovariectomized (OVX) and received a local estradiol-17β (estradiol) or cholesterol microimplant in several brain areas, such as the medial preoptic area (mPOA), paraventricular nucleus, ventromedial nucleus and arcuate nucleus (ARC), at 20 or 35 days of age. Six days after receiving the estradiol microimplant, animals were bled to detect LH pulses at 26 or 41 days of age, representing the pre- or postpubertal period, respectively. Estradiol microimplants in the mPOA or ARC, but not in other brain regions, suppressed LH pulses in prepubertal OVX rats. Apparent LH pulses were found in the postpubertal period in all animals bearing estradiol or cholesterol implants. It is unlikely that pubertal changes in responsiveness to estrogen are due to a change in estrogen receptor (ER) expression, because the number of ERα-immunoreactive cells and mRNA levels of Esr1, Esr2 and Gpr30 in the mPOA and ARC were comparable between the pre- and postpubertal periods. In addition, kisspeptin or GnRH injection overrode estradiol-dependent prepubertal LH suppression, suggesting that estrogen inhibits the kisspeptin-GnRH cascade during the prepubertal period. Thus, estrogen-responsive neurons located in the mPOA and ARC may play key roles in estrogen-dependent prepubertal restraint of GnRH/LH secretion in female rats.     

Effects of the phytoestrogen,genistein, and protein tyrosine kinase inhibitor–dependent mechanisms on steroidogenesis and estrogen receptor expression in porcine granulosa cells of medium follicles

The use of soy-based products in pig diets had raised concerns regarding the reproductive toxicity of genistein, the predominant isoflavone in soybeans. Genistein was reported to exhibit weak estrogenic activity but its mechanism of action is not fully recognized. The aim of the study was to examine the in vitro effects of genistein on (1) progesterone (P₄) and estradiol (E₂) secretion by porcine granulosa cells harvested from medium follicles, (2) the viability of cultured granulosa cells, and (3) the mRNA and protein expression of estrogen receptors α and β (ERα and ERβ) in these cells. In addition, to verify the role of protein tyrosine kinase (PTK)–dependent mechanisms possibly involved in genistein biological action, we tested the effects of lavendustin C, the nonsteroidal PTK inhibitor, on granulosa cell steroidogenesis. We found that genistein inhibited (P < 0.05) basal P₄ secretion by granulosa cells harvested from medium follicles of pigs. In contrast, lavendustin C did not affect basal P₄ secretion by the cells. Moreover, genistein increased (P < 0.05) basal granulosal secretion of E₂. In contrast, lavendustin C did not alter basal E₂ secretion by porcine granulosa cells. In addition, we demonstrated that genistein increased mRNA and protein expression of ERβ (P < 0.05) in the examined cells. The expression of ERα mRNA was not affected by genistein and ERα protein was not detected in the cultured granulosa cells of pigs. In summary, the genistein action on follicular steroidogenesis in pigs involved changes in the granulosal expression of ERβ. However, the genistein action on P₄ and E₂ production by granulosa cells harvested from medium follicles did not seem to be associated with PTK.     

Association of the estrogen receptor 1 and 2 polymorphisms with fat distribution in heavy pigs

More than 80% of Italy's pig production is used in the production of traditional dry cured ham. Dry cured ham production requires fresh legs with at least 15 mm of fat coverage. For decades, Italian pigs have been selected for fatness, as legs constitute almost 60% of the commercial value of the animal. Lately, however, thigh prices have dropped, increasing the economic importance of the Longissimus dorsi (L. dorsi) to the pig industry. This research sought to identify genes that can modulate fat repartitioning, resulting in fat legs and lean L. dorsi. As estrogens are known to control the distribution of body fat in humans and rodents, we investigated the polymorphisms in the estrogen receptor 1 (ESR^{PvuII5700/4200}) and estrogen receptor 2 (ESR2 A949G) genes in 612 pigs (278 females, 334 castrated males) and collected the following phenotypical data: carcass weight, lean percentage, leg weight, back fat and leg fat thickness. Castrated males of the ESR^{PvuII5700/5700} genotype had significantly more back fat (P < 0.05) with no significant effect on leg fat. Conversely, ESR^{PvuII5700/5700} females had significantly less leg fat (P < 0.05) with no significant effect on back fat. Both males and females of the ESR2 A949A genotype had less leg fat (P < 0.05) without any effect of the polymorphism on back fat. Our findings suggest that ESR^{PvuII5700/4200} and ESR2 A949G polymorphisms are associated with subcutaneous fat localization in pigs.     

Estradiol-17β and linseed meal interact to alter visceral organ mass and hormone concentrations from ovariectomized ewes

To evaluate the estrogenic potential of secoisolariciresinol diglycoside (SDG) found in linseed meal (LSM) on visceral organ mass, IGF-I, and thyroid hormone (T₃ and T₄) concentrations, 48 multiparous, ovariectomized ewes (54.6 ± 1.1 kg) were used in a 3 × 4 factorial arrangement. Main effects were length of LSM feeding (0, 1, 7, or 14 d) and length of exposure to estradiol-17β (E₂) implant (0, 6, or 24 h prior to tissue collection). Implanting ewes with E₂ for 24 h increased liver mass relative to empty body weight (EBW; g/kg EBW) compared with ewes implanted for 0 or 6 h (P ≤ 0.03), whereas feeding LSM for 14 d decreased liver mass compared with ewes fed LSM for 1 or 7 d (P ≤ 0.02). There was an LSM × E₂ interaction (P = 0.01) for duodenal mass (g/kg EBW), LSM, and E₂ tended (P = 0.07) to influence the stomach complex mass; however, ileal mass was not affected. Neither LSM nor E₂ affected (P ≥ 0.12) CYP2C or CYP3A mRNA expression or cellularity of the liver. Exogenous E₂ influenced circulating concentrations of IGF-I, T₃, and T₄. The estrogenic or anti-estrogenic potential of LSM is dependent upon the tissue, exposure to E₂, and the duration of LSM feeding. Feeding LSM during gestation, lactation, or during the grow-finish phase warrants further investigation.