Human corpus luteum secretion of relaxin, oxytocin, and progesterone

The transcriptome-wide N6-methyladenosine (m6A) map profiling reveals the regulatory role of m6A in the yak ovary

BACKGROUND AND AIM

Yak estrus is a seasonal phenomenon, probably involving epigenetic regulation of synthesis and secretion of sex hormones as well as growth and development of follicles. N6-methyladenosine (m⁶A) is the most common internal modification of the eukaryotic mRNA. However, there are no detailed reports on the m⁶A transcriptome map of yak ovary. Therefore, this study aimed to collected the yak ovarian tissues at three different states of anestrus (YO-A), estrus (YO-F), and pregnancy (YO-P), and obtained the full transcriptome m⁶A map in yak by MeRIP-seq.

RESULTS

The HE staining revealed that the number of growing follicles and mature follicles in the ovary during the estrus period was relatively higher than those in the anestrus period and the pregnancy period. The RT-qPCR showed that the expression of METTL3, METTL14, FTO, YTHDC1 were significantly different across different periods in the ovaries, which suggests that m⁶A may play a regulatory role in ovarian activity. Next, we identified 20,174, 19,747 and 13,523 m⁶A peaks in the three ovarian samples of YO-A, YO-F and YO-P using the methylated RNA immunoprecipitation sequencing (MeRIP-seq). The m⁶A peaks are highly enriched in the coding sequence (CDS) region and 3'untranslated region (3'UTR) as well as the conserved sequence of "RRACH." The GO, KEGG and GSEA analysis revealed the involvement of m⁶A in many physiological activities of the yak's ovary during reproductive cycle. The association analysis found that some genes such as BNC1, HOMER1, BMP15, BMP6, GPX3, and WNT11 were related to ovarian functions.

CONCLUSIONS

The comparison of the distribution patterns of methylation peaks in the ovarian tissues across different periods further explored the m⁶A markers related to the regulation of ovarian ovulation and follicular development in the yak ovary. This comprehensive map provides a solid foundation for revealing the potential function of the mRNA m⁶A modification in the yak ovary.

The Importance of Experimental Investigation of the Peripheral Oxytocin System

Oxytocin and oxytocin receptors are synthesized in the periphery where paracrine/autocrine actions have been described alongside endocrine actions effected by central release of oxytocin from the posterior pituitary. In the female reproductive system, classical actions of uterine contraction and milk ejection from mammary glands are accompanied by actions in the ovaries where roles in steroidogenesis, follicle recruitment and ovulation have been described. Steroidogenesis, contractile activity, and gamete health are similarly affected by oxytocin in the male reproductive tract. In the cardiovascular system, a local oxytocinergic system appears to play an important cardio-protective role. This role is likely associated with emerging evidence that peripheral oxytocin is an important hormone in the endocrinology of glucose homeostasis due to its actions in adipose, the pancreas, and the largely ignored oxytocinergic systems of the adrenal glands and liver. Gene polymorphisms are shown to be associated with a number of reported traits, not least factors associated with metabolic syndrome.

Key to Life: Physiological Role and Clinical Implications of Progesterone

The most recent studies of progesterone research provide remarkable insights into the physiological role and clinical importance of this hormone. Although the name progesterone itself means “promoting gestation”, this steroid hormone is far more than a gestational agent. Progesterone is recognized as a key physiological component of not only the menstrual cycle and pregnancy but also as an essential steroidogenic precursor of other gonadal and non-gonadal hormones such as aldosterone, cortisol, estradiol, and testosterone. Based on current findings, progesterone and novel progesterone-based drugs have many important functions, including contraception, treatment of dysfunctional uterine bleeding, immune response, and prevention of cancer. Considering the above, reproduction and life are not possible without progesterone; thus, a better understanding of this essential molecule could enable safe and effective use of this hormone in many clinical conditions.

Ocular Phenotype of Relaxin Gene Knockout (Rln-/-) Mice

Purpose: To test if relaxin deficiency affects ocular structure and function we investigated expression of relaxin (Rln) and RXFP receptors (Rxfp1, Rxfp2), and compared ocular phenotypes in relaxin gene knockout (Rln^-/- ) and wild type (Rln^+/+ ) mice. Materials and Methods: Rln, Rxfp1 and Rxfp2 mRNA expression was detected in ocular tissues of Rln+/+ mice using RT-PCR. The eyes of 11 Rln^-/- and 5 Rln^+/+ male mice were investigated. Corneal and retinal thickness was assessed using optical coherence tomography. Intraocular pressure was measured using a rebound tonometer. Retinal, choroidal and sclera morphology and thickness were evaluated histologically. Eyes were collected and fixed for immunofluorescence staining or used for RNA extraction to evaluate mRNA expression using real-time PCR. Results: Rln mRNA was expressed only in the retina, whereas Rxfp1 transcripts were detected in the retina, cornea and sclera/choroid. Rxfp2 was only present in the cornea. None of these genes were expressed in the lacrimal gland, eyelid or lens. Intraocular pressure was higher and central cornea of Rln^-/- mice was significantly thicker and had significantly larger endothelial cells and a lower endothelial cell density than Rln^+/+ mice. Immunohistochemistry demonstrated no significant difference in AQP3 and AQP5 staining in the cornea or other regions between wildtype and Rln^-/- mice. mRNA expression of Aqp4 was significantly higher in Rln^-/- than in Rln^+/+ corneas, whereas Col1a2, Mmp9, Timp1 and Timp2 were significantly decreased. Expression of Aqp1, Aqp4, Aqp5, Vim and Tjp1 was significantly decreased in Rln^-/- compared to Rln^+/+ uvea. No significant differences in these genes were detected in the retina. Retinal, choroidal and scleral thicknesses were not different and morphology appeared normal. Conclusion: The findings indicate that loss of Rln affects expression of several genes in the uvea and cornea and results in thicker corneas with altered endothelial cells. Many of the gene changes suggest alterations in extracellular matrix and fluid transport between cells.

Administration study of recombinant human relaxin-2 in horse for doping control purpose

The insulin-like peptide relaxin (RLX), an endogenous peptide hormone produced in human for pregnancy and reproduction, is also known to exert a range of physiological and pathological effects. Its use is banned in human sports, horseracing, and equestrian competitions due to its potential performance enhancing effect through vasodilation resulting in the increase of blood and oxygen supplies to muscles. Little is known about the biotransformation and elimination of RLX in horses. This paper describes an administration study of rhRLX-2 and its elimination in horses, and the development of sensitive methods for the detection and confirmation of rhRLX-2 in both horse plasma and urine by nano-liquid chromatography/high resolution mass spectrometry (nano-LC/HRMS) after immunoaffinity extraction with the objective of controlling the abuse of rhRLX-2 in horses. The limits of detection in plasma and urine are 2 pg/mL and 5 pg/mL, respectively. Two thoroughbred geldings were each administered one dose of 10 mg rhRLX-2 subcutaneously daily for 3 consecutive days. The rhRLX-2 could be detected and confirmed in the plasma and urine samples collected 105 h and 80 h, respectively, after the last dose of administration. For doping control purposes, rhRLX-2 ELISA could be used as a screening test to identify potential positive samples for further investigation using the nano-LC/HRMS methods.

Effect of Mode of Conception on Maternal Serum Relaxin, Creatinine, and Sodium Concentrations in an Infertile Population

OBJECTIVE

To investigate how the mode of conception affects maternal relaxin, creatinine, and electrolyte concentrations.

BACKGROUND

Pregnancies achieved by fertility treatment often begin in a nonphysiologic endocrine milieu with no corpus luteum (CL) or with many corpora lutea. The CL produces not only estradiol and progesterone but is also the sole source of relaxin in early pregnancy, a hormone that may contribute to maternal systemic and renal vasodilation. There is limited data about maternal physiology in early pregnancy during fertility treatment, and studies have rarely considered the potential effect of the absence of the CL. To begin to address this gap in knowledge, we sought to investigate how the mode of conception affects maternal relaxin, creatinine, and electrolyte concentrations.

METHODS

One hundred eighty-four women who received care at an academic infertility practice provided serum samples. Levels of relaxin 2, creatinine, and electrolytes were compared between 4 groups defined on the basis of mode of conception which corresponded to categories of CL number: (1) absence of the CL, (2) single CL, (3) multiple CL from ovarian stimulation not including in vitro fertilization (IVF), and (4) multiple CL from IVF with fresh embryo transfer.

RESULTS

Relaxin-2 levels were undetectable in patients lacking a CL. Creatinine, sodium, and total CO₂ levels were significantly higher in the 0 CL group (relaxin absent) compared to all other groups (relaxin present). Compared to clomiphene, use of letrozole was associated with a lower relaxin level.

CONCLUSION

Early creatinine and sodium concentrations are increased in the absence of relaxin. Given the increasing utilization of frozen embryo transfer, further studies comparing programmed with natural cycles are warranted.

Relaxin contributes to the regulation of arterial pressure in adult female mice

Relaxin is increasingly being recognized as a potent vasodilatory and antifibrotic hormone. Given that relaxin is present in the circulation during the luteal phase of the menstrual cycle and during pregnancy, when arterial pressure is lowest in women, relaxin may contribute to the relative cardiovascular protection observed in premenopausal women as compared with age-matched men and postmenopausal women. In the present study, we investigated the contribution of relaxin to the normal regulation of arterial pressure in adult female and male mice and during pregnancy. Mean arterial pressure (MAP) was measured via radiotelemetry in 14-week-old male and female wild-type (WT; C67BL/6xSv129) and relaxin knockout (KO) mice. Thereafter, female mice were time-mated with a (non-telemetered) male of the same genotype and MAP was measured throughout gestation. Basal MAP was ∼10 mmHg lower in WT females than males (P<0.05). Relaxin deficiency increased basal MAP in females (P<0.05 vs WT female), but not males. As expected, MAP decreased during gestation in WT mice. Conversely, in relaxin KO mice, arterial pressure increased during mid and late gestation (P<0.05 as compared with WT). Moreover, relaxin deficiency impaired gestational weight gain and reduced litter size. This is the first study to (i) demonstrate that relaxin contributes to the sexual dimorphism of arterial pressure in mice and (ii) document the changes in the arterial pressure profile of pregnant relaxin KO mice. Understanding the mechanisms that underlie the regulation of arterial pressure in premenopausal females may uncover new strategies to treat hypertension in women (non-pregnant and pregnant) and men.

The Intracellular Effect of Relaxin on Female Anterior Cruciate Ligament Cells

BACKGROUND

Female collegiate athletes with serum relaxin concentrations above 6.0 pg/mL have been shown to have more than 4 times increased risk for anterior cruciate ligament (ACL) tears. However, the intracellular effect of relaxin on ACL cells has not been elucidated.

HYPOTHESES

The hypotheses were that relaxin binding to receptors on female ACL cells will result in (1) an increase in matrix metalloproteinase (MMP) and decrease in tissue inhibitor of metalloproteinase (TIMP) gene expression, (2) a decrease in collagen and alpha smooth muscle actin (αSMA) expression, (3) inhibition of transforming growth factor β1 (TGFβ1)-induced fibrosis, and (4) an increase in cyclic adenosine 3',5'-monophosphate (cAMP) production and that these changes will not be observed in male ACL cells.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ligament cells from ACL tissue were isolated from 7 male and 7 female human donors and expanded in vitro. The cells were incubated with escalating concentrations of relaxin-2, as well as with TGFβ1 or 17β-estradiol in certain groups. Cells were then lysed and analyzed for MMP1 (collagenase-1), MMP3 (stromelysin-1), MMP13 (collagenase-3), TIMP1, type I collagen, type III collagen, and/or αSMA mRNA expression using quantitative real-time polymerase chain reaction. Intracellular cAMP levels were assessed via an enzyme-linked immunoassay.

RESULTS

ACL cells primed with estrogen and treated with 10 ng/mL and 100 ng/mL relaxin illustrated increased MMP1 expression (P = .012 and .006, respectively) and MMP3 expression (P = .005 and .001, respectively). Treatment with 100 ng/mL relaxin decreased αSMA expression (P = .001). When ACL tissue isolated from female donors with a history of oral contraceptive use was excluded from the analysis, 100 ng/mL of relaxin decreased type I collagen (P = .005) and type III collagen (P = .028) expression in cells primed with estrogen. Relaxin exhibited no significant effect on male-derived ACL cells.

CONCLUSION

Relaxin-2 significantly upregulated intracellular processes in human female ACL cells, but no effect was observed in male cells. Relaxin increased MMP (MMP1 and MMP3) and decreased αSMA and type I and III collagen expression, which may act to alter the structural integrity of the ACL tissue over time.

CLINICAL RELEVANCE

Female athletes with higher circulating relaxin levels may be more susceptible to ACL injury.

The role of relaxin in mare reproductive physiology: A comparative review with other species

Relaxin is a peptide hormone best known for its action during the latter half of pregnancy, in particular for its softening effect on pelvic ligaments that aids in preparation of the birth canal for the impending delivery of the fetus. The source of relaxin during early pregnancy varies across species, with the CL being the main source in a number of species. The main source of relaxin during late equine pregnancy is the placenta. In mares with impaired placental function, circulating relaxin levels decline before abortion. During early pregnancy, relaxin promotes endometrial angiogenesis through upregulating endometrial expression of vascular endothelial growth factor. The horse is unique in that the equine conceptus expresses relaxin messenger RNA as early as 8 days after ovulation, with levels increasing as conceptus development proceeds. Although secretion of functional relaxin has not been verified, it is likely, given that the embryo also expresses transcripts coding for enzymes processing the prohormone to yield the mature hormone. Furin, an enzyme which belongs to the subtilisin-like proprotein convertase family known to process preprorelaxin, appears to be the foremost convertase expressed by equine conceptuses. Conceptus-derived relaxin could drive endometrial angiogenesis and also act in an autocrine fashion to promote the embryo's own development. Relaxin is also expressed by ovarian structures during the nonpregnant estrous cycle. In the mare, follicular expression of relaxin is comparable among follicles of varying size and has been localized to granulosa and theca cells. In women and pigs, relaxin appears to promote follicular development. In the rat, multiple lines of evidence indicate that relaxin is involved in the ovulatory process. In the mare, relaxin might play a similar role in the ovulatory process, as in equine ovarian stromal cells relaxin promotes the secretion of gelatinases and tissue inhibitors of metalloproteinases; local proteolysis of the follicular wall is integral to the ovulatory process. However, functional studies addressing the role of relaxin in the ovulatory process are missing in the mare.

Relaxin Affects Smooth Muscle Biophysical Properties and Mechanical Activity of the Female Mouse Colon

The hormone relaxin (RLX) has been reported to influence gastrointestinal motility in mice. However, at present, nothing is known about the effects of RLX on the biophysical properties of the gastrointestinal smooth muscle cells (SMCs). Other than extending previous knowledge of RLX on colonic motility, the purpose of this study was to investigate the ability of the hormone to induce changes in resting membrane potential (RMP) and on sarcolemmal ion channels of colonic SMCs of mice that are related to its mechanical activity. To this aim, we used a combined mechanical and electrophysiological approach. In the mechanical experiments, we observed that RLX caused a decay of the basal tone coupled to an increase of the spontaneous contractions, completely abolished by the guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]-quinoxalin-1-one (ODQ). The electrophysiological results indicate for the first time that RLX directly affects the SMC biophysical properties inducing hyperpolarization of RMP and cycles of slow hyperpolarization/depolarization oscillations. The effects of RLX on RMP were abolished by ODQ as well as by a specific inhibitor of the cGMP-dependent protein kinase, KT5823. RLX reduced Ca(2+) entry through the voltage-dependent L-type channels and modulated either voltage- or ATP-dependent K(+) channels. These effects were abolished by ODQ, suggesting the involvement of the nitric oxide/guanylate cyclase pathway in the effects of RLX on RMP and ion channel modulation. These actions of RLX on membrane properties may contribute to the regulation of the proximal colon motility by the nitric oxide/cGMP/cGMP-dependent protein kinase pathway.

Recombinant human relaxin-2: (how) can a pregnancy hormone save lives in acute heart failure?

Acute heart failure (AHF) syndrome, characterized by pulmonary and/or venous congestion owing to increased cardiac filling pressures with or without diminished cardiac output, is still associated with high post-discharge mortality and hospitalization rates. Many novel and promising therapeutic approaches, among them endothelin-1, vasopressin and adenosine antagonists, calcium sensitization, and recombinant B-type natriuretic hormone, have failed in large studies. Likewise, the classic drugs, vasodilators, diuretics, and inotropes, have never been shown to lower mortality.The phase III trial RELAX-AHF tested recombinant human relaxin-2 (rhRlx) and found it to improve clinical symptoms moderately, to be neutral regarding the combination of death and hospitalization at day 60, to be safe, and to lower mortality at day 180. This review focuses on basic research and pre-clinical findings that may account for the benefit of rhRlx in AHF. The drug combines short-term hemodynamic advantages, such as moderate blood pressure decline and functional endothelin-1 antagonism, with a wealth of protective effects harboring long-term benefits, such as anti-inflammatory, anti-fibrotic, and anti-oxidative actions. These pleiotropic effects are exerted through a complex and intricate signaling cascade involving the relaxin-family peptide receptor-1, the glucocorticoid receptor, nitric oxide, and a cell type-dependent variety of kinases and transcription factors.

Progesterone regulates the expression and activity of two mouse isoforms of the glycoprotein folding sensor UDP-Glc: glycoprotein glucosyltransferase (UGGT)

UDP-Glucose:glycoprotein glucosyltransferase (UGGT) is a central component of the endoplasmic reticulum (ER) glycoprotein-folding quality control system, which prevents the exit of partially folded species. UGGT activity can be regulated by the accumulation of misfolded proteins in the ER, a stimulus that triggers a complex signaling pathway known as unfolded protein response (UPR) which is closely associated with inflammation and disease. In this work, we investigated the effect of progesterone (P4) on the expression and activity of UGGT in a mouse hybridoma. We detected the expression of two UGGT isoforms, UGGT1 and UGGT2, and demonstrated that both isoforms are active in these cells. Interestingly, the expression of each isoform is regulated by high physiological P4 concentrations. This work provides the first evidence of a hormonal regulation of UGGT isoform expression and activity, which might influence the glycoprotein quality control mechanism. These findings could contribute to the study of pathologies triggered by the accumulation of misfolded proteins.

Relaxin family peptides and their receptors

There are seven relaxin family peptides that are all structurally related to insulin. Relaxin has many roles in female and male reproduction, as a neuropeptide in the central nervous system, as a vasodilator and cardiac stimulant in the cardiovascular system, and as an antifibrotic agent. Insulin-like peptide-3 (INSL3) has clearly defined specialist roles in male and female reproduction, relaxin-3 is primarily a neuropeptide involved in stress and metabolic control, and INSL5 is widely distributed particularly in the gastrointestinal tract. Although they are structurally related to insulin, the relaxin family peptides produce their physiological effects by activating a group of four G protein-coupled receptors (GPCRs), relaxin family peptide receptors 1-4 (RXFP1-4). Relaxin and INSL3 are the cognate ligands for RXFP1 and RXFP2, respectively, that are leucine-rich repeat containing GPCRs. RXFP1 activates a wide spectrum of signaling pathways to generate second messengers that include cAMP and nitric oxide, whereas RXFP2 activates a subset of these pathways. Relaxin-3 and INSL5 are the cognate ligands for RXFP3 and RXFP4 that are closely related to small peptide receptors that when activated inhibit cAMP production and activate MAP kinases. Although there are still many unanswered questions regarding the mode of action of relaxin family peptides, it is clear that they have important physiological roles that could be exploited for therapeutic benefit.

Oxytocin receptors in the primate ovary: molecular identity and link to apoptosis in human granulosa cells

BACKGROUND

Oxytocin (OT) is produced by granulosa cells (GCs) of pre-ovulatory ovarian follicles and the corpus luteum (CL) in some mammalian species. Actions of OT in the ovary have been linked to luteinization, steroidogenesis and luteolysis. Human IVF-derived (h)GCs possess a functional OT receptor (OTR), linked to elevation of intracellular Ca(2+), but molecular identity of the receptor for OT in human granulosa cells (hGCs) and down-stream consequences are not known.

METHODS AND RESULTS

RT-PCR, sequencing and immunocytochemistry identified the genuine OTR in hGCs. OT (10 nM-10 microM) induced elevations of intracellular Ca(2+) levels (Fluo-4 measurements), which were blocked by tocinoic acid (TA; 50 microM, a selective OTR-antagonist). Down-stream effects of OTR-activation include a concentration dependent decrease in cell viability/metabolism, manifested by reduced ATP-levels, increased caspase3/7-activity (P < 0.05) and electron microscopical signs of cellular regression. TA blocked all of these changes. Immunoreactive OTR was found in the CL and GCs of large and, surprisingly, also small pre-antral follicles of the human ovary. Immunoreactive OTR in the rhesus monkey ovary was detected in primordial and growing primary follicles in the infantile ovary and in follicles at all stages of development in the adult ovary, as well as the CL: these results were corroborated by RT-PCR analysis of GCs excised by laser capture microdissection.

CONCLUSIONS

Our study identifies genuine OTRs in human and rhesus monkey GCs. Activation by high levels of OT leads to cellular regression in hGCs. As GCs of small follicles also express OTRs, OT may have as yet unknown functions in follicular development.

Corpus luteum function and regression

Several conclusions can be drawn from a review of the formation, function and regression of the corpus luteum. Ovulation and luteinization encompass degenerative and growth changes. Inflammatory conditions associated with ovulation lead to the breakdown of the follicle wall and the membrana granulosa, along with initial damage to theca and granulosa cells. The early corpus luteum is, therefore, a tissue in stress. Thus, one view of the corpus luteum is that it, like the phoenix, rises from the inflammatory ashes of the postovulatory follicle to exist briefly and to be consumed by a similar process at regression. The luteinization process is associated with parenchymal cell hypertrophy and matrix remodelling, which appear to be regulated by IGFs and androgens, and with angiogenesis, which is induced mostly by bFGF. High levels of functional activity of the corpus luteum are regulated by control at the level of the LH receptor, whose activation leads to the translocation of cholesterol into the cell and mitochondria for conversion to steroids. Functional luteal regression can be considered as another inflammatory-like condition with apparent activation of the immune system, along with cytokine, reactive oxygen, and eicosanoid production. Structural luteolysis is subsequently invoked that leads to matrix dissolution and cellular degeneration. It is perhaps not surprising that the invocation of immune activation, which causes the production of DNA-damaging reactive oxygen species and cytotoxic cytokines each cycle, may increase the risk of pathologies. One example may be ovarian cancer which appears to be associated with the use of fertility-enhancing drugs and associated with the number of ovulations in a woman's lifetime.

Relaxin as a natural agent for vascular health

Hypertension, atherothrombosis, myocardial infarction, stroke, peripheral vascular disease, and renal failure are the main manifestations of cardiovascular disease (CVD), the leading cause of death and disability in developed countries. Continuing insight into the pathophysiology of CVD can allow identification of effective therapeutic strategies to reduce the occurrence of death and/or severe disabilities. In this context, a healthy endothelium is deemed crucial to proper functioning and maintenance of anatomical integrity of the vascular system in many organs. Of note, epidemiologic studies indicate that the incidence of CVD in women is very low until menopause and increases sharply thereafter. The loss of protection against CVD in post-menopausal women has been chiefly attributed to ovarian steroid deficiency. However, besides steroids, the ovary also produces the peptide hormone relaxin (RLX), which provides potent vasoactive effects which render it the most likely candidate as the elusive physiological shield against CVD in fertile women. In particular, RLX has a specific relaxant effect on peripheral and coronary vasculature, exerted by the stimulation of endogenous nitric oxide (NO) generation by cells of the vascular wall, and can induce angiogenesis. Moreover, RLX inhibits the activation of inflammatory leukocytes and platelets, which play a key role in CVD. Experimental studies performed in vascular and blood cell in vitro and in animal models of vascular dysfunction, as well as pioneer clinical observations, have provided evidence that RLX can prevent and/or improve CVD, thus offering background to clinical trials aimed at exploring the broad therapeutic potential of human recombinant RLX as a new cardiovascular drug.

Effect of the oxytocin antagonist antocin and agonist decomoton on baboon luteal cell production and release of progesterone

OBJECTIVE

To evaluate the effect of oxytocin, its antagonist antocin, and agonist decomoton on baboon luteal cell P secretion.

DESIGN

Prospective study.

SETTING

Academic department of obstetrics and gynecology in a US medical school.

ANIMAL(S)

Luteal-phased timed corpora lutea (CL) from a cohort of adult cycling baboons (Papio anubis).

INTERVENTION(S)

Dispersed luteal cells from luteal phase baboon CL were cultured and treated with nothing (control), oxytocin (4-400 mU), antocin (4-400 microg), oxytocin with antocin, decomoton (4-400 microg), or oxytocin with decomoton.

MAIN OUTCOME MEASURE(S)

Basal and hCG (10 U)-stimulated P were measured in the incubate.

RESULT(S)

Basal P secretion did not change significantly with all peptides studied. The hCG-stimulated P secretion was significantly inhibited by oxytocin (4-400 mU), antocin (4-400 microg), and antocin combined with oxytocin, and with oxytocin, decomoton, and decomoton combined with oxytocin. Antocin (-12%) was less inhibitory than oxytocin (-25% to -22%). Antocin combined with oxytocin enhanced the inhibition to -35% to -39%. Decomoton had stronger (not significant) inhibition than oxytocin. Mean inhibition was 28%-35% with all doses of oxytocin, decomoton, or combined together.

CONCLUSION(S)

Although decomoton, an oxytocin agonist inhibited hCG-stimulated luteal cell P secretion in vitro, antocin also acted like an agonist, rather than an antagonist, in inhibiting P secretion.

Baboon corpus luteum: size and sex steroid secretion throughout the luteal phase

OBJECTIVE

To determine the size of the baboon corpus luteum (CL) and levels of plasma P, 17alpha-hydroxyprogesterone (17-OHP), and E2 in the ovarian vein draining it, the contralateral ovarian vein, and peripheral blood throughout the luteal phase of the menstrual cycle.

DESIGN

Prospective study.

SETTING

Academic department of obstetrics and gynecology in a US medical school.

ANIMAL(S)

Corpora lutea from a cohort of 27 adult cycling baboons (Papio anubis).

INTERVENTION(S)

Timed luteectomy.

MAIN OUTCOME MEASURE(S)

The authors weighed 166 CL and measured plasma P, 17-OHP, and E(2) in the blood samples obtained at luteectomy.

RESULT(S)

Early luteal phase corpora lutea weighed 189.1 +/- 12.3 mg (mean +/- SEM); their weight significantly increased to 239.4 +/- 8.4 mg at mid luteal phase and significantly declined to 188.3 +/- 14.0 mg in late luteal phase. Plasma P draining the CL (134.4 +/- 20.5 ng/mL in early, 167.4 +/- 18.7 ng/mL in mid, and 126.4 +/- 23.4 ng/mL in late luteal phase) was significantly higher than that in contralateral ovarian (11.0 +/- 1.4 ng/mL) and peripheral plasma (7.1 +/- 0.9 ng/mL). Similarly, levels of both plasma 17-OHP (10.9 +/- 1.5 to 15.9 +/- 2.4 ng/mL) and E2 (1.6 +/- 0.2 to 2.6 +/- 0.6 ng/mL) draining the CL were significantly higher than those from the contralateral ovary and peripheral blood (17-OHP, 1.1 +/- 0.2 ng/mL; E2, 0.2 +/- 0.05 ng/mL).

CONCLUSION(S)

Largest in mid luteal phase, the baboon CL secretes P, 17-OHP, and E2 throughout the luteal phase, with the highest levels seen in the ovarian vein draining the CL in the mid compared with the early and late luteal phases.

Physiology of Upward Transport in the Human Female Genital Tract

The uterus and fallopian tubes represent a functionally united peristaltic pump under the endocrine control of ipsilateral ovary. We have examined this function by using hysterosalpingoscintigraphy (HSS), recording of intrauterine pressure, electrohysterography, and Doppler sonography of the fallopian tubes. An uptake of labeled particles into the uterus was observed during the follicular and luteal phases of the cycle after application into the vagina. Transport into the oviducts, however, could only be demonstrated during the follicular phase. Furthermore, the predominant transport was into the tube ipsilateral to the ovary containing the dominant follicle. The pregnancy rate following spontaneous intercourse or insemination was higher in those women in whom ipsilateral transport could be demonstrated. The amount of material transported to the ipsilateral tube was increased after oxytocin administration, as demonstrated by radionuclide imaging and by Doppler sonography following instillation of ultrasound contrast medium. An increase in the basal tone and amplitude of contractions was observed after oxytocin administration. These results support the idea that the uterus and fallopian tubes act as a peristaltic pump, which increases transport of sperm into the oviduct ipsilateral to the ovary bearing the dominant follicle. Oxytocin appears to play a critical role in this peristaltic pump. A failure of the peristaltic mechanism is possibly responsible for infertility. We propose the term tubal transport disorder (TTD) as a nosological entity. Results from HSS could be a useful adjunct for choosing treatment modalities in patients with patent fallopian tubes suffering from infertility. These patients may be better served with in vitro fertilization (IVF).

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.

Day 14 maternal serum progesterone levels predict pregnancy outcome in IVF/ICSI treatment cycles: a prospective study

BACKGROUND

Serum progesterone has been advocated as a tool in the diagnosis of early pregnancy failure. We conducted this prospective study in order to investigate the potential value of early (14 days after oocyte recovery) serum progesterone measurement, in women undergoing IVF/ICSI and receiving rectal progesterone supplements, in relation to pregnancy outcome.

METHODS

442 women consecutively treated by IVF or ICSI had serum progesterone and bhCG levels prospectively measured 14 days after oocyte retrieval (day 0). All women received natural progesterone 400 mg rectally until the pregnancy test on day 14. Pregnant women were followed up by serial transvaginal ultrasound scans to 8 weeks gestation.

RESULTS

115 women (26%) had a viable intra-uterine pregnancy at 8 weeks gestation, 80 (18.1%) had an abnormal pregnancy (biochemical, ectopic, miscarriage) and 247 (55.9%) failed to conceive. Women with on-going pregnancies had significantly higher serum progesterone levels (median: 430, 95%CI: 390-500 nmol/l) compared to those who had either an abnormal pregnancy (72, 48-96 nmol/l; P < 0.001) or failed to conceive (33, 28-37 nmol/l; P < 0.001). Receiver-operator curve analysis demonstrated that a single serum progesterone on day 14 post-oocyte retrieval, could highly differentiate between normal and abnormal pregnancies (area under the curve = 0.927, 95%CI = 0.89-0.96; P < 0.0001).

CONCLUSIONS

In spite of exogenous progesterone supplementation, serum progesterone levels, from as early as 4 weeks gestation (day 14 post-oocyte retrieval) were significantly elevated and predicted women destined to have viable intra-uterine pregnancies. These high levels are suggestive that endogenous progesterone is already sufficient in viable pregnancies and that exogenous progesterone administration will not rescue a pregnancy destined to result in a miscarriage. Single serum progesterone measurement could be a useful indicator of pregnancy outcome in women undergoing IVF or ICSI treatment.

Relaxin depresses small bowel motility through a nitric oxide-mediated mechanism. Studies in mice

Gastrointestinal motility is reduced and the incidence of functional gastrointestinal disorders is increased in pregnancy, possibly due to hormonal influences. This study aims to clarify whether the hormone relaxin, which attains high circulating levels during pregnancy and has a nitric oxide-mediated relaxant action on vascular and uterine smooth muscle, also reduces bowel motility and, if it does, whether nitric oxide is involved. Female mice in proestrous or estrous were treated for 18 h with relaxin (1 microg s.c.) or vehicle (controls). Isolated ileal preparations from both groups were used to record contractile activity, either basal or after acute administration of relaxin (5 x 10(-8) M). Drugs inhibiting nitric oxide biosynthesis or neurotransmission were used in combination with relaxin. Expression of nitric oxide synthase isoforms by the ileum was assessed by immunocytochemistry and Western blot analysis. Relaxin caused a clear-cut decay of muscle tension and a reduction in amplitude of spontaneous contractions upon either chronic administration to mice or acute addition to isolated ileal preparations. These effects were significantly blunted by N(G)-nitro-L-arginine, but not by the neural blockers we used. Moreover, relaxin increased the expression of nitric oxide synthases II and III, but not synthase I. Relaxin markedly inhibits ileal motility in mice by exerting a direct action on smooth muscle through the activation of intrinsic nitric oxide biosynthesis.

Luteolysis: a neuroendocrine-mediated event

In many nonprimate mammalian species, cyclical regression of the corpus luteum (luteolysis) is caused by the episodic pulsatile secretion of uterine PGF2alpha, which acts either locally on the corpus luteum by a countercurrent mechanism or, in some species, via the systemic circulation. Hysterectomy in these nonprimate species causes maintenance of the corpora lutea, whereas in primates, removal of the uterus does not influence the cyclical regression of the corpus luteum. In several nonprimate species, the episodic pattern of uterine PGF2alpha secretion appears to be controlled indirectly by the ovarian steroid hormones estradiol-17beta and progesterone. It is proposed that, toward the end of the luteal phase, loss of progesterone action occurs both centrally in the hypothalamus and in the uterus due to the catalytic reduction (downregulation) of progesterone receptors by progesterone. Loss of progesterone action may permit the return of estrogen action, both centrally in the hypothalamus and peripherally in the uterus. Return of central estrogen action appears to cause the hypothalamic oxytocin pulse generator to alter its frequency and produce a series of intermittent episodes of oxytocin secretion. In the uterus, returning estrogen action concomitantly upregulates endometrial oxytocin receptors. The interaction of neurohypophysial oxytocin with oxytocin receptors in the endometrium evokes the secretion of luteolytic pulses of uterine PGF2alpha. Thus the uterus can be regarded as a transducer that converts intermittent neural signals from the hypothalamus, in the form of episodic oxytocin secretion, into luteolytic pulses of uterine PGF2alpha. In ruminants, portions of a finite store of luteal oxytocin are released synchronously by uterine PGF2alpha pulses. Luteal oxytocin in ruminants may thus serve to amplify neural oxytocin signals that are transduced by the uterus into pulses of PGF2alpha. Whether such amplification of episodic PGF2alpha pulses by luteal oxytocin is a necessary requirement for luteolysis in ruminants remains to be determined. Recently, oxytocin has been reported to be produced by the endometrium and myometrium of the sow, mare, and rat. It is possible that uterine production of oxytocin may act as a supplemental source of oxytocin during luteolysis in these species. In primates, oxytocin and its receptor and PGF2alpha and its receptor have been identified in the corpus luteum and/or ovary. Therefore, it is possible that oxytocin signals of ovarian and/or neural origin may be transduced locally at the ovarian level, thus explaining why luteolysis and ovarian cyclicity can proceed in the absence of the uterus in primates. However, it remains to be established whether the intraovarian process of luteolysis is mediated by arachidonic acid and/or its metabolite PGF2alpha and whether the central oxytocin pulse generator identified in nonprimate species plays a mediatory role during luteolysis in primates. Regardless of the mechanism, intraovarian luteolysis in primates (progesterone withdrawal) appears to be the primary stimulus for the subsequent production of endometrial prostaglandins associated with menstruation. In contrast, luteolysis in nonprimate species appears to depend on the prior production of endometrial prostaglandins. In primates, uterine prostaglandin production may reflect a vestigial mechanism that has been retained during evolution from an earlier dependence on uterine prostaglandin production for luteolysis.

In vitro microdialysis of baboon corpus luteum: effects of oxytocin on total and pulsatile progesterone secretion

Baboon corpora lutea (two each from the early, mid- and late luteal phases) were individually microretrodialyzed in vitro for 48 h, 12 h initial baseline, 12 h retrodialysis with OT (9 mU/h), 12 h without OT and 12 h with cAMP (5 mmol/h). Progesterone (P) was measured by a sensitive and specific radioimmunoassay in 10-min fractions of retrodialysates and analyzed for P peaks by PC-pulsar 3.0. Neither OT nor cAMP had any effect on the characteristics of P pulses. In early and late luteal phase CL, OT inhibited P secretion within 1 h of administration followed by increased P secretion late during OT perfusion. In midluteal phase, OT did not affect P secretion. In all CL, P secretion was sustained or further increased during the 12 h after stopping OT. cAMP also sustained baseline or stimulated P secretion. In contrast, OT either increased total P output/12 h (28 to 49% above baseline) with a further increase of 21% to 296% above baseline after stopping OT, or inhibited total P output by 4% to 13% percent with a further decline of 51% to 61% after stopping OT. Thus, while overall OT is luteotropic, its dual effect (initial inhibition followed by stimulation) suggests direct and indirect effects through paracrine-autocrine mechanisms.

Relaxin secretion in in vitro fertilization pregnancies

OBJECTIVE

This study was designed to determine whether the late luteal functional status of the corpora lutea in in vitro fertilization cycles alters the secretion of relaxin during pregnancy.

STUDY DESIGN

Analysis of serum relaxin, human chorionic gonadotropin, and steroid concentrations in sera of women with pregnancies viable beyond the twelfth week as a result of in vitro fertilization treatment was performed.

RESULTS

The serum estradiol and progesterone concentrations decreased 5.5- and 4-fold from days 5 to 6 after human chorionic gonadotropin to days 11 to 13 after human chorionic gonadotropin, respectively. The serum relaxin concentration increased 8-fold between the 11- to 15-day interval and the 16- to 50-day interval after human chorionic gonadotropin and another 6-fold to the 51- to 90-day interval after human chorionic gonadotropin (all p < 0.01). Multiple linear regression analysis showed that the serum estradiol level 11 to 13 days after human chorionic gonadotropin and the serum human chorionic gonadotropin level 11 to 15 days after human chorionic gonadotropin were the most powerful paired predictors of the concentration of serum relaxin measured in the 11- to 15-day interval after human chorionic gonadotropin interval (R2 = 0.39, n = 50), the 16- to 50-day interval (R2 = 0.61, n = 51), and the 51- to 90-day interval (R2 = 0.55, n = 39).

CONCLUSION

Secretion of relaxin is determined by an interaction of the late luteal functional status of the corpora lutea and the human chorionic gonadotropin secreted by the implanting pregnancy. These data allow for the hypothesis that inducing functional luteolysis by substituting one or more injections of luteinizing hormone for the human chorionic gonadotropin injection may decrease secretion of steroids, relaxin, and other factors from the corpora lutea during pregnancy, decreasing the risk of premature delivery in multiple gestations and the ovarian hyperstimulation syndrome.

The effect of ovulation induction on the concentration of maternal serum relaxin in twin pregnancies

OBJECTIVE

Our purpose was to determine the effects of fetal number, various ovulation induction treatments, and placental hormones on the concentration of maternal serum relaxin.

STUDY DESIGN

The concentrations of relaxin, human chorionic gonadotropin, estriol, and alpha-fetoprotein were determined in blood samples drawn at 16 to 18 weeks for prenatal diagnosis in 72 singleton and 115 twin pregnancies and analyzed by one-way analysis of variance, correlation analysis, and stepwise multiple linear regression of the log-transformed data.

RESULTS

The maternal serum concentrations of each of the four measured hormones were significantly higher in the twin pregnancies than in the singleton pregnancies: 1.4-fold for relaxin, 1.9-fold for human chorionic gonadotropin, 1.9-fold for estriol, and 2.2-fold for alpha-fetoprotein (all p < 0.01). The concentrations of each of the four hormones were significantly correlated with each of the others and with the number of fetuses (p < 0.01), except that estriol was not significantly correlated with human chorionic gonadotropin. The serum relaxin concentration in twin pregnancies after treatment with follicle-stimulating hormone and luteinizing hormone (menotropins) (n = 10) was 3.3-fold that in twins resulting from spontaneous ovulation (n = 89, p < 0.01). In twins resulting from in vitro fertilization or gamete intrafallopian transfer (n = 9) the serum relaxin concentration was 2.6-fold higher than in twins resulting from spontaneous ovulation (p < 0.01). The effect of clomiphene citrate (1.2-fold, n = 7) failed to reach statistical significance.

CONCLUSIONS

The second fetus causes a 1.4-fold increase in the concentration of maternal serum relaxin in twin pregnancies. Induction of ovulation with menotropins causes an additional 3.3-fold increase, whereas in vitro fertilization or gamete intrafallopian transfer treatment causes an additional 2.6-fold increase over that seen in twin pregnancies that followed spontaneous ovulation.

The prognostic value of serum progesterone and quantitative beta-human chorionic gonadotropin in early human pregnancy

OBJECTIVE

Our purpose was to determine whether serum progesterone, with or without quantitative beta-human chorionic gonadotropin, is predictive of pregnancy outcome within the first 8 weeks of gestation in asymptomatic women.

STUDY DESIGN

Asymptomatic patients at < 8 menstrual weeks' gestation were prospectively evaluated. The enrollment protocol included history, physical examination, ultrasonographic confirmation, and blood sample collection for beta-human chorionic gonadotropin and progesterone. The association between progesterone and beta-human chorionic gonadotropin values and pregnancy outcome was determined by logistic regression analysis. A receiver-operator characteristic curve was generated on the basis of the sensitivity and specificity of progesterone results.

RESULTS

Seventy-four patients were evaluated in this study. The mean serum progesterone level for viable pregnancies was 22.1 ng/ml, which was significantly greater than that for the nonviable gestations, 10.1 ng/ml (p < 0.001). A single progesterone level was predictive of pregnancy outcome (p < 0.001). The probability of an abnormal pregnancy outcome with a serum progesterone level < or = 6 ng/ml was 81%. A single beta-human chorionic gonadotropin level did not contribute to the prediction of pregnancy outcome (p = 0.59).

CONCLUSIONS

Serum progesterone alone, within the first 8 weeks of gestation, is predictive of pregnancy outcome.

Effects of oophorectomy and estrogen treatment on basal levels and 24-h profiles of oxytocin

The regulation of oxytocin is incompletely understood and data indicate that in addition to several neurotransmitters, estrogens may be involved. The aim of the present study was to investigate the effects of oophorectomy and hormonal replacement therapy (HRT) on basal levels and 24-h profiles of oxytocin. Basal levels of oxytocin were measured in 95 women who had undergone hysterectomy and who were divided into three groups: group A (n = 30), oophorectomized (BSO), not on HRT; group B (n = 32), BSO, receiving HRT; and group C (n = 33), ovaries preserved and not receiving HRT. The 24-h profiles of oxytocin were measured in nine women before and after hysterectomy. Continuous venous blood sampling was performed 1 week before surgery and 6-7 weeks after surgery for all nine women. Thereafter, three of the four oophorectomized women started replacement therapy with transdermal estradiol 50 micrograms/day. After 10 weeks of treatment, a third sampling was performed. Exogenous estrogen administration was associated with increased oxytocin levels and negative correlation between oxytocin and follicle stimulating hormone/luteinizing hormone levels was found. Removal of the ovaries did not reduce oxytocin levels in any of the investigated groups. When 24-h values were analyzed, no specific rhythmic or pulsatile pattern before or after hysterectomy, with or without simultaneous oophorectomy, was found.

The pharmacokinetics of recombinant human relaxin in nonpregnant women after intravenous, intravaginal, and intracervical administration

The pharmacokinetics of recombinant human relaxin (rhRlx) after intravenous (iv) bolus administration and the absorption of rhRlx after intracervical or intravaginal administration were determined in nonpregnant women. The study was conducted in two parts. In part I, 25 women received 0.01 mg/kg rhRlx iv. After a minimum 7-day washout period, these women were dosed intracervically (n = 10) or intravaginally (n = 15) with 0.75 or 1.5 mg rhRlx, respectively, in 3% methylcellulose gel. Part II was a double-blind, randomized, three-way crossover study in 26 women. At 1-month intervals, each woman received one of three intravaginal treatments consisting of 0 (placebo), 1, or 6 mg rhRlx in 3% methylcellulose gel. The serum concentrations of relaxin following iv administration were described as the sum of three exponentials. The mean (+/- SD) initial, intermediate, and terminal half-lives were 0.09 +/- 0.04, 0.72 +/- 0.11, and 4.6 +/- 1.2 hr, respectively. Most of the area under the curve was associated with the intermediate half-life. The weight-normalized clearance was 170 +/- 50 mL/hr/kg. The observed peak concentration was 98 +/- 29 ng/mL, and the weight-normalized initial volume of distribution was 78 +/- 40 mL/kg, which is approximately equivalent to the serum volume. If central compartment elimination was assumed, the volume of distribution at steady state (Vss/W) was 280 +/- 100 mL/kg, which is approximately equivalent to extracellular fluid volume. Vss/W could be as large as 1300 +/- 400 mL/kg without this assumption.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro decidualization of human endometrial stromal cells

Stromal cells isolated from proliferative human endometrium undergo morphologic and biochemical changes when exposed to a mixture of ovarian hormones, acquiring characteristics of decidual cells. In addition to the previously reported progestin-induced secretion of prolactin (PRL) by explants of human proliferative endometrium, and of PRL and laminin by stromal cells in culture, "in vitro" induction of several other decidual cell products was demonstrated in the present study, using cultures of stromal cells isolated from proliferative endometrium. Incubation of stromal cells with a mixture of estradiol, medroxyprogesterone acetate and relaxin, at a concentration reported to yield maximal stimulation of PRL production, resulted in changes from elongated to rounder cells, approx. 90% of which showed immunostaining for PRL under these conditions. Immunocytochemical procedures were carried out on cytospins of decidual cells isolated from decidual tissue adherent to fetal membranes collected at delivery (positive controls), and on stromal cells cultured in Lab-Tek chamber-slides, in the absence (negative controls) or in the presence of added hormones. Antibodies to 24K (a heat-shock protein also named HRP27), desmin (present in intermediate filaments), p29 (a protein associated with the estrogen receptor), and PP12 (an insulin growth factor-1 binding protein), did not react with stromal cells isolated from proliferative endometrium but showed immunostaining of the rounder cells obtained after hormonal treatment when tested with the peroxidase-labeled second antibody complex. In another series of similar experiments, in which the same decidualization end-points were employed, changes in 24K, desmin and PP12 expression were obtained by adding to the insulin-containing medium PRL instead of the hormonal mixture, a finding suggesting sequential steps during the decidualization process.

Laboratory and clinical comparison of a rapid versus a classic progesterone radioimmunoassay for use in determining abnormal and ectopic pregnancies

A rapid, solid-phase, nonextraction progesterone kit (n = 36) was compared with an established extraction method, liquid phase tritium radioimmunoassay for progesterone (n = 79). Logistic regression of the rapid method over the extraction method gave a correlation coefficient of r = 0.968. Logistic regression gave a discriminatory zone (abnormal vs normal pregnancy) of 22.58 ng/ml by the rapid method compared with 15 ng/ml for the extraction method (log Y = 0.253 + 0.936 log X). Similar sensitivity (100% and 100%), specificity (63% and 59%), and predictive values of positive and negative tests (positive predictive value = 91% and 75%, negative predictive value = 100% and 100%) were found using a discriminatory level of 15 and 20 ng/ml for the extraction method (n = 79) and rapid method (n = 76), respectively. Clinically, curettage for patients with values less than these discriminatory zones would have given unacceptable rates for termination of a potentially normal pregnancy (38%). Clinical comparison of abnormal (ectopic or abortion) and normal (term pregnancy) outcomes in two populations of women presenting with first-trimester bleeding revealed that progesterone levels would accelerate the workup in only a small percentage (27%, 15 of 56) of patients with ectopic pregnancies. The rate of ruptured ectopic pregnancies in the observed patients was similar (20%, 3 of 15) to studies using progesterone levels prospectively. Therefore in this retrospective analysis progesterone levels would have given no greater benefit than conventional management.

COOH-terminally-extended processing forms of oxytocin in human ovary

Human granulosa cells synthesize and secrete the oxytocin hormone. We have already shown that oxytocin-Gly, the last post-translational maturation intermediate of pro-hormone, is largely secreted by cultured granulosa cells deprived of ascorbate (Plevrakis et al. (1990) J. Endocrinol. 124, R5-R8). Using a combination of high performance liquid chromatography and radioimmunoassay, the oxytocin-like material present in human granulosa cell extracts, in follicular fluid, in cultured granulosa cell supernatants and in corpora lutea extracts was identified. We have demonstrated the presence of oxytocin-Gly, oxytocin-Gly-Lys and oxytocin-Gly-Lys-Arg, the same post-translational maturation intermediates as those we identified in bovine corpus luteum secretory granules. Thus we conclude that post-translational maturation of pro-oxytocin/neurophysin in human ovary proceeds by the same proteolytic events as those we described in bovine post-pituitary gland and corpus luteum.

The endocrinology of parturition in the human

Current evidence suggests that oestrogens, progesterone, relaxin, the prostaglandins, and oxytocin are all hormones concerned to a major degree with the onset and maintenance of parturition. Oestrogens, relaxin, and the prostaglandins are particularly involved with cervical ripening, while prostaglandins, progesterone and oxytocin are more involved in regulating myometrial contractility. Catecholamines may also have some regulatory function in relation to uterine contractions. Progesterone dominance during pregnancy is associated with a firm closed cervix, few myometrial gap junctions, low calcium levels in the cells, and a quiescent myometrium. At term, a change in the oestrogen/progesterone balance favours cervical ripening and increased uterine activity. Of particular importance at the level of the muscle cell are changes in the number of oxytocin receptors; a complex interaction between cAMP and phosphoinositide metabolism governs the intracellular level of calcium, thus regulating contractile activity.

Spontaneously resorbing ectopic pregnancy: preservation of human chorionic gonadotropin bioactivity despite declining steroid hormone levels

We compared serum hormone profiles of patients with normal intrauterine pregnancies (n = 14), spontaneously resorbing ectopic pregnancies (n = 10), and viable ectopic pregnancies (n = 26). Hormone profiles were evaluated at 5 to 8 weeks' gestational age. Ectopic pregnancies were diagnosed by laparoscopy; intrauterine gestations were confirmed by ultrasonography. Immunoreactive beta-human chorionic gonadotropin, progesterone, estradiol, and 17-hydroxyprogesterone were measured by radioimmunoassay. Bioactive human chorionic gonadotropin was measured by a modified mouse Leydig cell bioassay. Diminished steroid production was noted in ectopic pregnancies; levels in serum of patients with resorbing ectopic pregnancies were lower than values expressed in viable ectopic pregnancies (p less than 0.01). Serum levels of human chorionic gonadotropin bioactivity correlated closely with immunoreactive human chorionic gonadotropin in all three groups (r = 0.81, p less than 0.01). Ratios of bioactive human chorionic gonadotropin to immunoreactive beta-human chorionic gonadotropin were similar (0.93 +/- 0.26 in resorbing ectopic pregnancies, 1.11 +/- 0.16 in viable ectopic pregnancies, and 0.90 +/- 0.10 in intrauterine pregnancies). We conclude that although reduced serum levels of steroids noted in ectopic pregnancy suggest an impairment in corpus luteum activity, diminished steroid production was not attributable to lower human chorionic gonadotropin bioactivity.

Expression of the human relaxin gene in the corpus luteum of the menstrual cycle and in the prostate

DNA-RNA hybridization has been used to assess the presence of relaxin gene transcripts in human luteal tissues of pregnancy and the menstrual cycle, as well as in the human testis and prostate. The results imply a substantial capacity for hormone biosynthesis in the mid to late luteal phase of the ovary in non-pregnant women. In men the prostate has been shown also to express relaxin gene transcripts, though levels are low. The testis appears negative. The results suggest that functions for relaxin must be sought also outside pregnancy.