Relaxin: a product of the human corpus luteum of pregnancy

Optimal Endometrial Preparation Protocols for Frozen-thawed Embryo Transfer Cycles by Maternal Age

This retrospective cohort study aimed to explore the optimal endometrial preparation protocols among different maternal age groups. A total of 16,867 frozen-thawed embryo transfer (FET) cycles were categorized into three groups based on endometrial preparation protocols: Natural cycle (NC n = 3893), artificial cycles (AC, n = 11456) and AC with GnRH-a pretreatment (AC+GnRH-a, n = 1518). To account for repeat cycles, a generalized estimating equation (GEE) method was applied to examine the associations between cycle regimens and pregnancy outcomes. Subgroup analyses were conducted to evaluate the best preparation methods for different maternal age groups. Primary outcomes were live birth and early miscarriage rates. After completing GEE, in overall population, the live birth rate [(NC as reference; AC: adjusted odds ratio (aOR) = 0.837, 95% confidential interval (CI) 0.771-0.908; AC+GnRHa: aOR = 0.906, 95%CI 0.795-1.031)] in NC was significantly higher than that in AC, while comparable that in AC+GnRH-a. The early miscarriage rate (AC: aOR = 1.420, 95%CI 1.225-1.646; AC+GnRHa: aOR = 1.545, 95%CI 1.236-1.931) was significantly lower in NC compared to either AC group. Subgroup analysis showed that in younger women, the incidences of live birth (AC: aOR = 0.900, 95%CI 0.804-1.007; AC+GnRHa: aOR = 1.091, 95%CI 0.904-1.317) were equivalent between groups, with a slightly higher in AC+GnRH-a. Early miscarriage rate (AC: aOR = 1.462, 95%CI 1.165-1.835; AC+GnRHa: aOR = 1.137, 95%CI 0.948-1886) was only significantly lower in NC compared to that in AC. In older women, the live birth rate (AC: aOR = 0.815, 95%CI 0.722-0.920; AC+GnRHa: aOR = 0.759, 95%CI 0.627-0.919) was significantly higher, and early miscarriage rate (AC: aOR = 1.353, 95%CI 1.118-1.638; AC+GnRHa: aOR = 1.704, 95%CI 1.273-2.280) was significantly lower in NC compared to either AC group. Our study demonstrated that NC is associated with lower early miscarriage late in overall IVF population. There is a mild favor of AC+GnRH-a in younger women, while the priority of NC is remarkable in older women. Maternal age should be a considerable factor when determining endometrial preparation method for FET.

Potential influence of the corpus luteum on circulating reproductive and volume regulatory hormones, angiogenic and immunoregulatory factors in pregnant women

Cardiovascular function is impaired and preeclampsia risk elevated in women conceiving by in vitro fertilization (IVF) in the absence of a corpus luteum (CL). Here, we report the serial evaluation of hormones and other circulating factors in women who conceived with (or without) IVF. After a prepregnancy baseline, the study participants (n = 19-24/cohort) were evaluated six times during pregnancy and once postpartum (~1.6 yr). IVF pregnancies were stratified by protocol and CL number, i.e., ovarian stimulation (>1 CL) or hypothalamic-pituitary suppression (0 CL) versus spontaneous conceptions (1 CL). Results include the following: 1) relaxin was undetectable throughout pregnancy (including late gestation) in the 0 CL cohort, but markedly elevated in ~50% of women in the >1 CL cohort; 2) progesterone, plasma renin activity, and aldosterone transiently surged at 5-6 gestational weeks in the >1 CL group; 3) soluble vascular endothelial growth factor-1 (sFLT-1) abruptly increased between 5-6 and 7-9 gestational weeks in all three participant cohorts, producing a marked elevation in sFLT-1/PLGF (placental growth factor) ratio exceeding any other time point during pregnancy; 4) sFLT-1 was higher throughout most of gestation in both IVF cohorts with or without abnormal obstetrical outcomes; 5) during pregnancy, C-reactive protein (CRP) increased in 0 and 1 CL, but not >1 CL cohorts; and 6) plasma protein, but not hemoglobin, was lower in the >1 CL group throughout gestation. The findings highlight that, compared with spontaneously conceived pregnancy, the maternal milieu of IVF pregnancy is not physiologic, and the specific perturbations vary according to IVF protocol and CL status.

Developing a deeper insight into reproductive biomarkers

The development of biomarkers of reproductive medicine is still in its infancy because many black boxes are still present in reproductive medicine. Novel approaches to human infertility diagnostics and treatment must be developed because reproductive medicine has lagged behind in the implementation of biomarkers in clinical medicine. Despite the dearth of the available literature, the current rapid pace of publications suggests that this gap will soon be filled therefore; this review is a précis of the research that has been done so far and will provide a basis for the development of biomarkers in reproductive medicine.

Human relaxins (RLNH1, RLNH2), their receptor (RXFP1) and fetoplacental growth

Relaxin, a systemic and placental hormone, has potential roles in fetoplacental growth. Human placenta expresses two RLN genes, RLNH1 and RLNH2 Maternal obesity is common and is associated with abnormal fetal growth. Our aims were to relate systemic and cord blood RLNH2, placental RLNs and their receptor (RXFP1) with fetoplacental growth in context of maternal body mass index, and associations with insulin-like growth factor 2 (IGF2) and vascular endothelial growth factor A (VEGFA) in the same placentas. Systemic, cord blood and placental samples were collected prior to term labor, divided by prepregnancy body mass index: underweight/normal (N = 25) and overweight/obese (N = 44). Blood RLNH2 was measured by ELISA; placental RLNH2, RLNH1, RXFP1, IGF2 and VEGFA were measured by quantitative immunohistochemistry and mRNAs were measured by quantitative reverse transcription PCR. Birthweight increased with systemic RLNH2 only in underweight/normal women (P = 0.036). Syncytiotrophoblast RLNH2 was increased in overweight/obese patients (P = 0.017) and was associated with placental weight in all subjects (P = 0.038). RLNH1 had no associations with birthweight or placental weight, but was associated with increased trophoblast and endothelial IGF2 and VEGFA, due to female fetal sex. Thus, while systemic RLNH2 may be involved in birthweight regulation in underweight/normal women, placental RLNH2 in all subjects may be involved in placental weight. A strong association of trophoblast IGF2 with birthweight and placental weight in overweight/obese women suggests its importance. However, an association of only RLNH1 with placental IGF2 and VEGFA was dependent upon female fetal sex. These results suggest that both systemic and placental RLNs may be associated with fetoplacental growth.

Neuroendocrine mechanisms in pregnancy and parturition

The complex mechanisms controlling human parturition involves mother, fetus, and placenta, and stress is a key element activating a series of physiological adaptive responses. Preterm birth is a clinical syndrome that shares several characteristics with term birth. A major role for the neuroendocrine mechanisms has been proposed, and placenta/membranes are sources for neurohormones and peptides. Oxytocin (OT) is the neurohormone whose major target is uterine contractility and placenta represents a novel source that contributes to the mechanisms of parturition. The CRH/urocortin (Ucn) family is another important neuroendocrine pathway involved in term and preterm birth. The CRH/Ucn family consists of four ligands: CRH, Ucn, Ucn2, and Ucn3. These peptides have a pleyotropic function and are expressed by human placenta and fetal membranes. Uterine contractility, blood vessel tone, and immune function are influenced by CRH/Ucns during pregnancy and undergo major changes at parturition. Among the others, neurohormones, relaxin, parathyroid hormone-related protein, opioids, neurosteroids, and monoamines are expressed and secreted from placental tissues at parturition. Preterm birth is the consequence of a premature and sustained activation of endocrine and immune responses. A preterm birth evidence for a premature activation of OT secretion as well as increased maternal plasma CRH levels suggests a pathogenic role of these neurohormones. A decrease of maternal serum CRH-binding protein is a concurrent event. At midgestation, placental hypersecretion of CRH or Ucn has been proposed as a predictive marker of subsequent preterm delivery. While placenta represents the major source for CRH, fetus abundantly secretes Ucn and adrenal dehydroepiandrosterone in women with preterm birth. The relevant role of neuroendocrine mechanisms in preterm birth is sustained by basic and clinic implications.

Expression of LGR7 in the primate corpus luteum implicates the corpus luteum as a relaxin target organ

In women, the corpus luteum is the source of circulating relaxin. No previous studies have addressed whether the corpus luteum is also a relaxin target organ. We determined relaxin receptor LGR7 mRNA expression in human term pregnancy corpora lutea and nonhuman primate corpora lutea obtained during the menstrual cycle. Real-time reverse transcription-PCR demonstrated the expression of LGR7 mRNA in both human and rhesus monkey corpora lutea. Rhesus monkey corpora lutea were obtained from naturally cycling animals following documented luteinizing hormone (LH) surges at early, mid-, mid-late, and late luteal phases. Luteal expression of LGR7 mRNA did not show temporal variation. Since the primate corpus luteum is LH dependent, we assessed LGR7 mRNA expression in corpora lutea from rhesus monkeys treated with a gonadotropin-releasing hormone (GnRH) antagonist, which significantly suppressed pituitary LH levels. GnRH antagonist treatment, which also inhibits both progesterone and relaxin production, resulted in a fivefold increase in luteal LGR7 mRNA expression. These data suggest that luteal LGR7 mRNA expression may be regulated by relaxin and/or LH and that the primate corpus luteum is a target organ for relaxin.

Serum biomarkers of tubal ectopic pregnancy: current candidates and future possibilities

Ectopic pregnancy remains a considerable cause of maternal morbidity and mortality worldwide. Currently, it is diagnosed using a combination of transvaginal ultrasound and serial serum beta-human chorionic gonadotrophin levels. Diagnosis is often delayed and these tests are time-consuming and costly, both psychologically to the patient and financially to health services. The development of a biomarker that can differentiate a tubal ectopic from an intrauterine implantation is therefore important. In the pre-genomic era, a one-by-one scientific approach has revealed over 20 candidate biomarkers that could be used as a test to diagnose ectopic pregnancy although at present their clinical utility is very limited. These biomarkers cluster into themes: markers of abnormal embryo/trophoblast growth, markers of abnormal corpus luteum function, markers of a growing pregnancy in the Fallopian tube, markers of inflammation and peritoneal irritation, and uterine markers of normal implantation. It is likely that this thematic approach will facilitate the identification of newer biomarkers using microarray technology and inform the development of investigative paradigms using multiple markers at the time of presentation.

Mechanisms of Relaxin-Mediated Premature Birth

In women, circulating relaxin is produced by the corpus luteum of pregnancy. The levels of relaxin are predominantly determined by the luteal mass, the number of corpora lutea present. Relaxin levels are highest after ovulation induction, which stimulates formation of many corpora lutea. Elevated relaxin levels in the first trimester of pregnancy are maintained throughout pregnancy and are linearly related to preterm birth. In an in vitro model of late human pregnancy cervix, relaxin increases MMP-1 and MMP-3 and decreases TIMP-1 levels, thus acting as a positive regulator of matrix metalloproteinases. In an in vivo rhesus monkey model of early pregnancy, relaxin decreases cervical collagen content, decreases cervical lumican levels, and stimulates MMP-7 levels. Early effects of relaxin in the uterus include increasing endometrial arteriole number and increasing the number of leukocytes, uterine natural killer cells, macrophages, and neutrophils. These cells release many cytokines which contribute to changes that stimulate and facilitate uterine contractility. If these changes persist in late pregnancy, relaxin may be a mediator of labor. Excess relaxin may produce these changes at an accelerated rate, causing preterm birth.

Increased Expression of the Relaxin Receptor (LGR7) in Human Endometrium during the Secretory Phase of the Menstrual Cycle

This study investigated localization and expression of relaxin and its receptor, LGR7, in the human endometrium during the proliferative and secretory phases of the menstrual cycle. H2 relaxin binding was identified in endometrium, but not myometrium, and particularly in the epithelium of the endometrial glands and uterine lumen. Binding sites increased in the early secretory phase of the menstrual cycle and were paralleled by similar increases in LGR7 mRNA measured by Q-PCR. The increase in LGR7 expression and H2 relaxin binding in the secretory phase of the menstrual cycle suggests a specific role for relaxin after ovulation in the human uterus.

Increased risk of preterm birth in singleton pregnancies resulting from in vitro fertilization–embryo transfer or gamete intrafallopian transfer: A meta-analysis

OBJECTIVE

To perform a systematic review of the literature to determine whether singleton pregnancies resulting from IVF-ET/GIFT are at higher risk for preterm birth (<37 weeks).

DESIGN

Literature search and systematic review.

SETTING

Medical school.

INTERVENTION(S)

A MEDLINE search (1965-2000) was performed using the terms "premature labor," "infertility," "pregnancy complications," "gonadotropins," "pregnancy outcome," "preterm delivery," and "in vitro fertilization." Criteria for inclusion were English language, original research article, study patients conceived using IVF-ET (with or without intracytoplasmic sperm injection) or GIFT, pregnancy outcome reported compared with a control group (e.g., naturally conceived singletons at their hospital or a national reference), and prematurity clearly defined. Incomplete articles (e.g., abstracts), reports of other studies, and studies that failed to separate multiple from singleton gestations were excluded.

MAIN OUTCOME MEASURE(S)

Summary of relative risks of preterm birth.

RESULT(S)

Twenty-seven articles met all inclusion/exclusion criteria and were analyzed by meta-analysis. The random-effects summary relative risk of preterm birth in singleton pregnancies resulting from IVF-ET/GIFT was 1.98 (95% confidence interval, 1.77-2.22).

CONCLUSION(S)

The risk of preterm birth in singleton pregnancies resulting from IVF-ET/GIFT is twice that of natural conceived pregnancies.

Relaxin regulation of endometrial structure and function in the rhesus monkey

Despite the documented importance of the protein hormone relaxin in reproduction in various mammalian species, the role of relaxin in human reproduction is poorly understood, largely because of the lack of studies in women or in suitable non-human primate models. Here we describe the establishment of a non-human primate model of early human pregnancy and its use in defining the actions of relaxin. Results demonstrate that relaxin exerts dramatic uterine effects including pronounced increase in uterine weight and stimulation of endometrial angiogenesis and resident endometrial lymphocyte number. In addition, relaxin decreases endometrial levels of matrix metalloproteinases 1 and 3 and increases levels of their endogenous inhibitor, tissue inhibitor of metalloproteinase 1, resulting in maintenance of endometrial collagen content. Relaxin significantly inhibits endometrial levels of estrogen receptor alpha, but not beta, and of progesterone receptor isoforms A and B. The findings that relaxin stimulates new blood vessel formation and increases cytokine-containing lymphocyte number while maintaining endometrial connective tissue integrity are consistent with a significant role of relaxin in the establishment and/or maintenance of early pregnancy.

Abnormal relaxin secretion during pregnancy in women with type 1 diabetes

To test the hypothesis that relaxin may play a role in the fetal abnormalities associated with pregnancy in type 1 diabetic women, we previously compared gestational relaxin concentrations in diabetic and clinically normal women using a porcine relaxin radioimmunoassay (RIA): Serum immunoactive relaxin was significantly (P < 0.001) elevated in the diabetic women. To confirm and extend this work in a larger group of subjects, we have now used an enzyme-linked immunosorbent assay (ELISA) specific for human H2 relaxin (the normal human gene product) to determine immunoactive serum relaxin concentrations in serial samples from 61 Type 1 diabetic and 21 normal pregnant women. Samples from 22 of the diabetic and nine of the normal women were also directly compared in the porcine relaxin RIA. ELISA-determined serum relaxin was higher (P < 0.001) at 24 and 36 weeks of pregnancy in type 1 diabetic women than in controls, confirming previous findings. However, the geometric mean increase in immunoactive relaxin concentration in identical samples from pregnant diabetic women over that of controls was significantly greater with the RIA than with the ELISA (271% vs 44%; P < 0.001). To investigate this discrepancy, the specificity and epitope selectivity of the RIA and the ELISA were compared using several synthetic polypeptides, including human relaxins H1 and H2, and relaxin and insulin derivatives. Both assays showed great specificity, but the porcine RIA selectively identified the epitopes of the receptor-binding domain of the relaxin B chain and cross-reacted strongly with H1 and H2 relaxins. In contrast, only the H2 peptide was detected by the ELISA antiserum. Therefore, the marked discrepancy between the RIA and the ELISA could be due to the presence in the diabetic samples of another relaxin-like molecule in addition to the normal H2 relaxin. The biological consequences of elevated serum relaxin in diabetic pregnancy remain to be elucidated.

Relative activity and specificity of promoters from prostate-expressed genes

BACKGROUND

To evaluate their relative activity and specificity for prostate cells promoter and regulatory regions from three prostate-expressed genes-prostate-specific antigen (PSA), probasin, and relaxin H2-have been compared in prostate cell lines and in lines of breast, bladder, liver, kidney, lung, and ovarian origin.

METHODS

After transfection into different cell types, the activity of promoters was assayed using linked reporter genes and normalized against that of the Rous sarcoma virus. Activity was measured both in the presence and in the absence of co-transfected androgen receptor (AR).

RESULTS

PSA and probasin regulatory regions showed strong responsiveness to co-transfection of the AR in most cell types. The core PSA promoter region showed low activity and specificity, but the specificity and level of expression were substantially increased by inclusion of upstream sequences, particularly the enhancer region. Probasin promoter fragments showed specificity of expression for prostate cell lines but required AR for significant levels of expression. Relaxin promoter fragments directed significant AR-inducible expression in prostate cells but showed little specificity and variable AR responsiveness in other cell types.

CONCLUSIONS

Of regulatory regions tested, a 430-base pair probasin promoter and PSA enhancer/core promoter showed the best combination of AR-stimulated prostate cell expression with limited expression in other cell types.

Gonadotropin-releasing hormone agonist and human menopausal gonadotropin (hMG) short protocol, but not hMG alone, rescues the corpus luteum from the preceding cycle

OBJECTIVE

To determine whether ovulation induction regimens, particularly the short protocol, has an effect on the corpus luteum (CL) from the previous cycle.

DESIGN

Infertility patients were followed in an academic research environment. Patients were treated with either the short protocol (GnRH agonist [GnRH-a] and hMG) or hMG alone in a controlled ovarian hyperstimulation cycle.

SETTING

Infertility center in academic setting.

PATIENTS

Patients requiring ovulation induction.

INTERVENTIONS

The blood samples were drawn on day 2 or 3 as a baseline before initiation of any treatments, generally on day 5 and usually every other day thereafter until ovulation. Serum P, E2, and relaxin were determined.

MAIN OUTCOME MEASURES

Serum P, E2 and relaxin.

RESULTS

Patients receiving hMG alone showed no change in serum P levels in the first few days of treatment whereas most short-protocol patients (18/30; 60%) showed an increase of P within 3 days of the initiation of treatment. The increase in P almost always was associated with an increase in relaxin as a marker of the luteal production of this P.

CONCLUSION

The short protocol with its flare of gonadotropins is able to stimulate the CL from the previous cycle, resulting in an early increase in P that comes from the CL as indicated by its association with an increased relaxin in the same subjects.

Direct effect of gonadotropins on decidualization of human endometrial stroma cells

Decidualization of stromal cells isolated from proliferative human endometrium was achieved by adding to the culture medium human gonadotropins (FSH, FSH + LH, hCG). In addition to changes in the morphology of the stromal cells to the decidual phenotype, decidualization was evident from the expression of prolactin (PRL), demonstrated immunocytochemically, by Western blotting analysis, and by measuring its output into the medium through solid phase enzyme immunoassay. Gonadotropins also induced cAMP formation in the endometrial stromal cells under the same experimental conditions. This finding suggests that the mechanism by which gonadotropins promote decidualization of human endometrial stromal cells in vitro involves the introduction of cAMP, a compound that we have found to elicit the expression of PRL in this system. PRL is likely to be a key intermediate in the process of decidualization since it is by itself capable of inducing differentiation of the endometrial stromal cells to the decidual phenotype. Awareness of direct actions of gonadotropins on the endometrial cells and, in particular, of the decidualizing effects of FSH (Metrodin), FSH+LH (Pergonal) and hCG may contribute to the understanding of physiologic as well as pathophysiologic conditions relevant to endometrial functions and fertility.

The relationship between hCG and relaxin secretion in normal pregnancies vs peri-implantation spontaneous abortions

OBJECTIVE

We determined the ovarian response to human chorionic gonadotrophin (hCG) in terms of relaxin and progesterone secretion during the peri-implantation period of normal and failing pregnancies. We wished to test the hypotheses that relaxin production in failing pregnancies is different from that in normal pregnancies, that relaxin is a reliable, quantitative indicator of the biological activity of endogenous hCG, and that relaxin is a useful predictor of peri-implantation spontaneous abortions.

DESIGN

Daily blood samples were collected in a prospective longitudinal study from insemination patients.

PATIENTS

Women undergoing artificial insemination in natural cycles with non-frozen donor semen at a University clinic.

MEASUREMENTS

Serum LH, hCG, relaxin and progesterone were measured and the relationship between hCG and the ovarian hormones was evaluated in the peri-implantation period of normal pregnancies and spontaneous abortions.

RESULTS

Nine of 23 conceptive cycles resulted in a spontaneous abortion between 16 and 70 days after the LH peak. In all normal and failing pregnancies there was a close qualitative relationship between hCG secretion and relaxin production. Six of nine failing pregnancies were associated with abnormally low hCG secretion. Six of the spontaneous abortions were associated with rates of relaxin secretion which were higher than the mean of 14 normal pregnancies. No such alterations in progesterone concentrations were observed. In cases where hCG was extremely low, the quantitative relationship between hCG and relaxin was different from that in cases of normal hCG concentrations.

CONCLUSIONS

There is a close temporal relationship between the secretion of trophoblastic hCG and ovarian secretion of relaxin in the peri-implantation period of normal and failing pregnancies. In failing pregnancies there is substantial variability in the quantitative relationship between relaxin and hCG, indicating that relaxin is not a reliable quantitative indicator of hCG bioactivity. Contrary to previous reports, relaxin concentrations in failing pregnancies tended to be higher than or equal to concentrations in normal pregnancies until the loss was imminent. Because of this relaxin is not a useful predictor of peri-implantation spontaneous abortions.

Maternal relaxin concentrations in diabetic pregnancy

Maternal serum concentrations of relaxin, an insulin homologue produced both by the corpus luteum of pregnancy and by the fetoplacental unit, are highest in the first trimester and fall to their lowest level in the third trimester. Relaxin is thought to influence carbohydrate metabolism in the uterus, and it has been suggested that serum concentrations of relaxin in diabetic women are higher than those of non-diabetic women. We show that maternal serum relaxin concentrations are significantly higher at each stage of pregnancy in insulin-dependent diabetic mothers than in non-diabetic mothers. This elevation in relaxin concentrations is not related to other indices of diabetic control. The physiological importance of the higher concentrations of relaxin in the serum of diabetic women--in particular, whether they contribute to the higher incidence of major anomalies in the fetuses of diabetic mothers--is yet to be determined.

The disposition of a human relaxin (hRlx-2) in pregnant and nonpregnant rats

The pharmacokinetics and tissue distribution of a human relaxin were investigated after intravenous (iv) bolus administration to pregnant or nonpregnant rats. Human gene-2 relaxin (hRlx-2) serum concentrations after iv bolus administration were described as the sum of three exponentials. The pharmacokinetics were comparable in pregnant and nonpregnant rats. The serum clearance (CL) was 7.4-10.2 ml/min/kg at doses of 46-93 micrograms/kg and was linear in this range. The half-lives were 1.1-2.0, 15.1-16.4, and 53.7-67.9 min, respectively. The volume of the central compartment (Vc) was 48-79 ml/kg and the volume of distribution at steady state (Vss) was 271-336 ml/kg. Increasing the dose to 463 micrograms/kg increased the dose-corrected area under the serum concentration-time curve and significantly decreased CL and Vss. The distribution of radioactivity in the tissues of pregnant rats was followed after iv bolus dosing with hRlx-2 internally labeled with 35S-cysteine. Comparison of the extent of organ uptake of radiolabel after 35S-hRlx-2 or 35S-cysteine administration suggested that the kidneys were the principal site of uptake; the liver was of secondary importance. In perfusion experiments utilizing livers isolated from pregnant or nonpregnant rats, 36-52% of the dose of hRlx-2 was cleared from the perfusate in 2 hr. These studies showed that the pharmacokinetics of hRlx-2 in rats appeared to be unaffected by pregnancy and suggested that the kidneys and liver both play a role in the elimination of hRlx-2.

The role of the adenylyl cyclase system in the regulation of corpus luteum function in the human and in nonhuman primates

We have reviewed the properties of luteinizing hormone/human chorionic gonadotropic (LH/hCG)-sensitive adenylyl cyclase (AC) of human corpus luteum (CL) and its regulation by several hormones and nonhormonal activators. We have also described the changes in enzyme activity in membrane preparations of human and cynomolgus monkey CL obtained at various stages of the menstrual cycle and pregnancy. The data have been analyzed with respect to the functional status of the luteal tissue and to the species differences among primate CL. In the menstrual cycle, luteal AC responsiveness to LH/hCG was detectable during the midluteal phase, but not during the late luteal phase or in the follicular phase of the following cycle. In addition, nonhormonal stimulation was high in CL obtained during the midluteal and late luteal phases, but declined drastically by the follicular phase of the next cycle. In early pregnancy, the enzyme was unresponsive to LH/hCG stimulation, yet its sensitivity to nonhormonal stimulation was similar, if not identical, to that of midluteal phase CL. Functional activity was also evident at the end of pregnancy. These results demonstrate that expression of AC activity in primate luteal membrane changes significantly with varying hormonal status under physiologic conditions. It is concluded that the AC system in luteal membranes is an effective model to study the mechanisms that regulate function and life span of the human and nonhuman primate CL.

Relaxin as an aetiological factor in diabetic embryopathy

Relaxin, an insulin homologue, has effects on collagen resembling those of certain teratogenic agents. It is suggested that diabetic embryopathy could be due to disturbances of relaxin secretion during fetal organogenesis.

Serum relaxin concentrations in women following the administration of 16,16-dimethyl-trans-delta 2-PGE1 methyl ester during early pregnancy

Serum relaxin was estimated in 11 women during termination of first-trimester pregnancy with 16,16-dimethyl-trans-delta 2-PGE1 methyl ester (16 DM-PGE1). Vaginal administration of 16 DM-PGE1 was associated with a significant increase in serum relaxin.

Partial purification of relaxin from human seminal plasma

Human seminal plasma contains approximately 50 ng/ml of relaxin (specific activity = 1.3 ng/mg protein). During preliminary purification, semen plasma was delipidated, rehydrated, and loaded onto small octadecyl silica columns that were eluted with a TEAF/acetonitrile gradient system. Results were monitored by radioimmunoassay. The resultant partially purified human relaxin demonstrated biologic activity in the rat uterine segment bioassay. Nine liters of semen plasma was delipidated, rehydrated in TEAF, and subjected to high-performance liquid chromatography by a step gradient followed by a linear gradient. The active eluate was further purified by ion exchange chromatography. Pooled recovery fractions provided a total of 45.8 micrograms of relaxin. An aliquot flash evaporated and desalted by gel filtration chromatography provided 1.85 micrograms of relaxin in 25.2 mg protein, specific activity 73.4. This material is being used as immunogen in the production of antihuman relaxin antibodies by monoclonal technique. Our procedure represents the first and only successful partial purification of human relaxin to yield sufficient quantity and purity for antibody production.

Paracrine regulation of follicular maturation in primates

Taken together, the studies reviewed here suggest that although gonadotropins are necessary for follicular growth, they are insufficient by themselves to explain the dynamics of folliculogenesis. Indeed, the role of gonadotropins in follicular maturation must necessarily be permissive: that is LH and FSH initiate a synchronized cascade of follicular events directly mediated by paracrine and autocrine factors.

High-performance liquid chromatography of amino acids, peptides and proteins. LXIII. Reversed-phase high-performance liquid chromatographic characterisation of several polypeptide and protein hormones

The chromatographic behaviour on alkylsilicas of a variety of hormonal proteins is described. Optimization of resolution and recovery of these protein hormones, which included porcine relaxins, human chorionic gonadotropin, human placental lactogen, pituitary derived growth hormone and adenohypophyseal glycoprotein hormones, was achieved by manipulation of both mobile and stationary phase parameters. With standard stainless-steel analytical columns (10-30 cm X 0.4 cm) packed with meso- or macro-porous n-alkylsilica supports these proteins can be readily fractionated at the semi-preparative level with separation times generally under 90 min using elution systems directly compatible with subsequent methods of primary structure determination or biological functional analysis. The effects of changes in several experimental parameters on peak symmetry, retention and recovery are described.

Immunoreactive relaxin surge in the peritoneal fluid of women during the midluteal phase

Relaxin was assayed in the peritoneal fluid (PF) of 176 women with normal ovulatory cycles. Validation of the assay in this fluid was carefully established. Relaxin was rarely detected before day 20 of the cycle. From days 21 to 24, all samples contained detectable concentrations of the peptide, ranging between 75 and 775 pg/ml. Apparition of relaxin in the PF was not directly related to the ovulatory follicular rupture. It was also delayed, compared with the postovulatory rise of plasma and peritoneal progesterone. Relaxin is thus present in the PF only during the period propitious to human embryo implantation.

The occurrence of relaxin in hyperstimulated human preovulatory follicles collected in an in vitro fertilization program

The avidin-biotin immunoperoxidase method and antisera against highly purified porcine relaxin were utilized to localize relaxin-like immunoreactivity in biopsied specimens from six preovulatory follicles from four women undergoing laparoscopy for oocyte retrieval in an in vitro fertilization program. By histological criteria, three of the follicles were luteinized and three were not. Relaxin was found in the granulosa cells of those cells which showed histological luteinization, whereas no relaxin was found in the nonluteinized preovulatory follicles. Our results show, for the first time, the occurrence of relaxin in the human ovary before ovulation and they suggest that the appearance of relaxin is related to the luteinization process.

Management of endocrine disorders in pregnancy. Part II. Pituitary, ovarian and adrenal disease

Images

Relaxin in human decidua and term placenta

Using both a homologous porcine RIA and 3 bioassays, we investigated the relaxin content of human decidua from first trimester and term gestations and of placentas at term. Aqueous extracts of these tissues yielded only between 211 and 1090 pg immunoreactive relaxin/g fresh tissue. Neither acetonehexane extraction, octadecylsilica cartridge elution nor molecular sieve chromatography increased these relaxin levels. Compared with term decidua, first trimester decidua contained significantly higher levels of immunoreactive relaxin. In vitro studies did not evidence significant relaxin production by either decidual or placental tissues, even in the presence of decidual prolactin production. These results are in direct contrast to earlier reports of high concentrations of relaxin in decidua and placenta.

Immunohistochemical demonstration of relaxin in gynecologic tumors

The immunoperoxidase technique was utilized to study the occurrence and localization of relaxin in malignant and nonmalignant trophoblastic disease and nontrophoblastic gynecologic cancer. Tissue specimens were studied from normal placenta at various weeks of gestation (N = 10), hydatidiform mole (N = 10), invasive mole (N = 10), choriocarcinoma (N = 10), normal endometrium (N = 28), decidua (N = 5), adenocarcinoma of the endocervix (N = 10), of the endometrium (N = 10), corpus luteum (N = 2), ovarian serous papillary cystadenocarcinoma (N = 10), and mucinous cystadenocarcinoma (N = 10). Relaxin was identified in the syncytiotrophoblast of normal placenta at all stages of gestation and also, for the first time, in hydatidiform mole, invasive mole, and choriocarcinoma. No relaxin was found in any nontrophoblastic cancer, including secretory-type adenocarcinoma. The absence of relaxin in the secretory-type endometrial adenocarcinoma is intriguing in light of the finding of relaxin in the normal secretory endometrium. The difference may be due to absence of the relaxin-producing corpus luteum in cancer patients or to loss of relaxin synthesis in the malignant endometrium. The results of this study suggest that relaxin may be synthesized by the normal syncytiotrophoblast and trophoblastic tumors, although differential absorption of relaxin produced in another site cannot be excluded.

Synergistic effect of human relaxin and progesterone on human myometrial contractions

In an in vitro human myometrial strip system, both relaxin and progesterone can independently decrease the amplitude of spontaneous myometrial contractions. However, progesterone and relaxin synergize in this action. Doses of relaxin and progesterone which independently are ineffective, together inhibit myometrial contraction amplitude. Relaxin and progesterone are both products of the corpus luteum, a structure necessary for early pregnancy maintenance. The synergistic action of relaxin and progesterone in vitro suggests a similar in vivo physiologic effect in establishing uterine quiescence.

Relaxin--a review

Relaxin is a polypeptide hormone, similar in structure to insulin and has been found in the female of all species studied. The corpus luteum of pregnancy is the main source of relaxin in many species but in others the decidua is apparently of greater importance. It has also been found in other tissues; e.g. prostatic fluid, testis and ovary. First discovered and extracted from the corpora lutea of pregnant sows in an impure form in 1926, it was found to relax the pubic ligament of the oestrogen primed guinea-pig. It was named after this action, but has since been found to have many other possible roles, including preparation of the endometrium for implantation, inhibition of uterine activity in early pregnancy, remodelling of the uterine stroma during pregnancy, cervical ripening and the initiation of parturition. Relaxin's main cellular action in pregnancy may be to drive collagen biosynthesis in its target organs, thus facilitating the remodelling of the connective tissue. Due to the impurity of relaxin preparations used in clinical trials until the mid-1970's, the role of relaxin in the human has been in doubt. Porcine and rat relaxins have now been highly purified and their detailed structure is known. Human relaxin awaits adequate isolation, purification and characterization, and is not yet available for laboratory and clinical trials. However, the recent preparation of purified porcine relaxin for clinical trials and the availability of specific radioimmunoassays for this relaxin together with the identification of relaxin receptor sites, are rapidly helping to establish the concept that relaxin is indeed an important hormone both in human reproduction and in other physiological processes.

Myometrial inhibiting activity of relaxin-containing extracts of human corpora lutea of pregnancy

Relaxin is a peptide hormone secreted by the human corpus luteum of pregnancy . Aqueous extracts of relaxin-rich pregnancy corpora lutea decreased the amplitude of spontaneous human myometrial strip contractions in vitro. Relaxin-poor extracts of menstrual cycle corpora lutea did not affect contractions. Antibody precipitation of relaxin from pregnancy luteal extracts eliminated the effect on myometrial strips. Relaxin removal was confirmed by bioassay. This demonstrates an inhibiting action of human relaxin on human myometrial tissue in vitro. This action suggests a mechanism for maintaining uterine quiesence in early pregnancy.

Serum relaxin levels in prostaglandin E2 induced abortions

Relaxin, a peptide hormone produced only by the corpus luteum of pregnancy, can be used as a marker of luteal function in human pregnancy. Serum immunoreactive relaxin levels were measured serially in six women having second trimester abortions induced with intravaginal prostaglandin E2 (PGE2) suppositories. All patients aborted within 17 hours of the first suppository. No significant changes were detectable in serum relaxin levels in any of the patients. It is concluded that PGE2 does not interfere with the corpus luteum's ability to secrete relaxin in the second trimester of human pregnancy.