Relaxin positively regulates matrix metalloproteinase expression in human lower uterine segment fibroblasts using a tyrosine kinase signaling pathway

Despite the importance of relaxin to normal parturition in various species and its potential as an etiological agent in preterm delivery in women, knowledge regarding the mechanisms by which relaxin alters cervical connective tissue is extremely limited. An established in vitro model for human pregnancy cervix, human lower uterine segment fibroblasts, was used to determine the effects of relaxin as well as those of progesterone on the expression of matrix metalloproteinases and tissue inhibitor of metalloproteinase-1. The results demonstrate that relaxin is a positive regulator of matrix metalloproteinase expression, as it stimulates the expression of procollagenase protein and mRNA levels, stimulates prostromelysin-1 protein and mRNA levels, and inhibits tissue inhibitor of metalloproteinase-1 protein expression. Stimulation of procollagenase and prostromelysin-1 expression by relaxin does not involve phorbol-12-myristate-13-acetate- sensitive PKCs. Relaxin-stimulated tyrosine phosphorylation of the putative receptor and inhibition by a receptor tyrosine kinase inhibitor suggest that the relaxin receptor is probably a tyrosine kinase receptor. Inhibition of c-Raf protein expression using an antisense oligonucleotide inhibits relaxin regulation of matrix metalloproteinase and tissue inhibitor of metalloproteinase-1, suggesting that a signaling pathway involving c-Raf kinase mediates relaxin action.

The preterm prediction study: maternal serum relaxin, sonographic cervical length, and spontaneous preterm birth in twins

OBJECTIVE

The risk of spontaneous preterm birth has been related to decreased cervical length and to increased serum relaxin. To explore a relationship between these findings, we used data collected from two prior studies to correlate relaxin levels with cervical length and risk of spontaneous preterm birth in women with twin pregnancies.

METHODS

In a secondary analysis of data collected in two previous observational studies of risk factors for preterm birth, relaxin levels in maternal serum and cervical length were measured at 24 (n= 188) and 28 (n= 145) weeks in women with spontaneous twin pregnancies. Relaxin, as a continuous variable, was related by logistic regression analysis to risk of spontaneous preterm birth before 37, 35, and 32 weeks' gestation, and by Spearman correlation coefficients to cervical length at 24 and 28 weeks. Cervical length at 24 weeks was known to be correlated with spontaneous preterm birth before 37, 35, and 32 weeks (P =.03,.01, and.002, respectively) in this study population.

RESULTS

Cervical length did not correlate with relaxin levels at 24 (P=.601) or 28 (P=.304) weeks. Relationships between relaxin and spontaneous preterm birth were observed at 24 weeks for births before 37 weeks (odds ratio [OR] 1.56, 95% confidence interval [CI] 1.00, 2.44; P=.05), and at 28 weeks for births before 35 weeks (OR 1.97, 95% CI 1.05, 3.70; P=.034) and 32 weeks (OR 2.43, 95% CI 1.01, 5.83; P=.048).

CONCLUSION

The absence of an association between relaxin and cervical length suggests that increased relaxin does not explain the inverse correlation between cervical length and spontaneous preterm birth in women with spontaneous twin pregnancies.

Luteal progesterone relates to histological endometrial maturation in fertile women

To examine the relationship between endometrial histological maturation and reproductive hormones, we studied 11 fertile women, aged 18-37 yr. All participants had had at least 1 previous pregnancy and cycled regularly, every 25-35 days. Women collected daily, first morning voided urine for measurement of estradiol and progesterone metabolite excretion, estrone conjugates (E1c), and pregnanediol glucuronide (Pdg), respectively, throughout the cycle of study. Hormones were normalized for creatinine. Between 7-9 days after home detection of a LH surge (Sure Step), participants underwent an endometrial biopsy using a small bore (Pipelle) catheter. Tissue was prepared for histological and biochemical analyses. The histological analysis is reported herein. Endometrium was dated by 3 authors (N.S., D.H., and S.P.), all of whom were blinded to the participant's identity or timing of biopsy within her cycle. Final dating was agreed upon based upon the method of Noyes et al. E1c and Pdg were integrated throughout the cycle using the trapezoidal rule, and correlations were sought between deviation from expected histology (based upon urinary hormones and LH surge) and integrated hormone values. E1c varied over a 2-fold range in these normal women, from 1196-2040 ng/cycle. Pdg excretion was much more variable, ranging from 22-119 microg/cycle. No relationship could be found between histological lagging of endometrial maturation and lower excretion of E1c. A moderate correlation was observed (Spearman's r = 0.6; P < 0.05) between degree of histological maturation and integrated Pdg. Of two women with evidence of a disparity between gland and stromal development (glands lagging behind stroma by >2 days), one excreted 24 microg Pdg/cycle, the next to lowest value. We conclude that normal fertile women experience a wide range of hormone concentrations in the face of normal endometrial maturation. Progesterone appears to exert a dose-related effect on endometrial maturation, and the techniques we used, although relatively crude clinical measures, appeared to be sufficient to detect this relationship.

Endothelin stimulation of rat uterine segment contractility is estrogen-dependent

To determine whether the effect of endothelin upon in vitro uterine contractility requires estrogen, immature female Long Evans rats were subcutaneously injected daily for 3 days with either estradiol benzoate or vehicle. The uterine contractile response to endothelin (5 or 100 nM) was measured. A response to endothelin in vehicle-treated animals exposed to physiologic (5.6 mM) or high (70.6 mM) potassium levels was also noted. Vehicle-treated uteri did not respond to endothelin; the contractions in estrogen-treated uteri increased by 288%. With high potassium, and without estrogen, no response to endothelin was seen. These data indicate that the contractile effect of endothelin on the uterus requires estrogen.

Elevated maternal serum relaxin concentrations throughout pregnancy in singleton gestations after superovulation

OBJECTIVE

To test the hypothesis that superovulation results in elevated maternal circulating relaxin concentrations throughout the second and third trimesters of pregnancy, independent of the pattern of hCG secretion.

METHODS

Two groups of women with singleton gestations were studied: a group of nine women who achieved pregnancy after stimulation with human menopausal gonadotropin and a group of six women who achieved pregnancy without prior stimulation. Peripheral blood samples were drawn approximately every 5 weeks throughout the second and third trimesters. Serum relaxin concentrations were measured using a human relaxin-specific enzyme-linked immunosorbent assay; hCG was measured by an immunofluorometric assay.

RESULTS

The stimulated group had significantly higher relaxin levels throughout pregnancy (P=.007, multivariate analysis of variance) than did nonstimulated controls. The mean relaxin level in stimulated patients was 1.78 ng/mL (95% confidence interval [CI] 1.5, 2.17) and in nonstimulated subjects the level was 0.73 ng/mL (95% CI 0.59, 1.25). Spline fits demonstrated that stimulated patients had higher relaxin levels throughout the second and third trimesters. There was no significant difference in hCG concentrations between the two groups (P=.61).

CONCLUSION

In singleton gestations after superovulation, maternal serum relaxin concentrations are significantly higher throughout the second and third trimesters of pregnancy. These differences are independent of the pattern of hCG secretion. It appears that luteal relaxin secretion is controlled by factors in addition to hCG.

Demonstration of a relaxin receptor and relaxin-stimulated tyrosine phosphorylation in human lower uterine segment fibroblasts

To elucidate the mechanism of relaxin action, we studied the binding characteristics of human relaxin and its effects on intracellular concentrations of cAMP and tyrosine phosphorylation of cellular proteins in a model system of human cervix, human lower uterine segment fibroblasts. Human relaxin labeled with 125I bound specifically to a single class of high-affinity relaxin binding sites, distinct from insulin receptors, with a mean (+/-SEM) dissociation constant (Kd) of 4.36 +/- 1.7 x 10(-9) M and a mean of 3220 +/- 557 binding sites per cell in human lower uterine segment fibroblasts. Relaxin, in quantities that were shown previously to stimulate intracellular levels of cAMP in other cell types, had no effect on intracellular levels of cAMP in human lower uterine segment fibroblasts even in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine (IBMX). Incubation of the cells with relaxin caused a significant increase in tyrosine phosphorylation of a protein with an apparent Mr of approximately 220 kDa in these cells. In concert with results of recent studies that demonstrated that the Mr of the relaxin receptor is approximately 220 kDa, our data suggest that the phosphorylated protein is likely to be the relaxin receptor.

Dogfish shark (Squalus acanthias) testes contain a relaxin

Relaxin is a 6-kd polypeptide that exerts important hormonal effects in many female mammals. Relaxin is produced by the ovary, placenta, or uterus in many mammalian species. The functions of relaxin in the male mammal are not yet firmly established, but there is some evidence suggesting an exocrine effect on sperm motility and fertilizability. In the male mammals that have been studied, relaxin is produced by the prostate gland (human) or seminal vesicles (boar). However, in the bird, the testis is the likely source of relaxin. Among the elasmobranchs, ovaries obtained from dogfish sharks have been shown to contain a polypeptide hormone that is structurally, biologically, and immunologically similar to mammalian relaxins, but the male reproductive tract of this species has not previously been investigated as a potential source of relaxin. Extracts of testes obtained from mature dogfish sharks have now been tested by a specific relaxin bioassay and by a homologous porcine radioimmunoassay for the presence of relaxin. Both crude and partially purified testicular extracts contained unmistakable guinea pig pubic symphysis-"relaxing" activity and relaxin-like immunoactivity. Following immunoaffinity purification, the shark testis polypeptide had an apparent specific activity of 88 microg porcine relaxin equivalents per milligram in the radioimmunoassay, which is similar to the immunoactivity of pure shark ovarian hormones. These data, therefore, strongly support the view that in dogfish sharks, the male as well as the female gonad produces relaxin. Furthermore, as the dogfish shark has existed as a species for about 200 million years, the data suggest that testicular relaxin appeared early in vertebrate evolution.

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.

Use of synthetic canine relaxin to develop a rapid homologous radioimmunoassay

Canine relaxin (cRlx) was synthesized by a combination of solid-phase methods and sequential site-directed disulfide bond formation. Proof that the intended molecule had been synthesized was obtained by analytical HPLC of the intact and reduced molecule, by amino acid and sequence analysis, and by receptor binding and in vivo mouse interpubic ligament bioassays. Antisera to synthetic cRlx were raised in six male rabbits; these cross-reacted with relaxins of other species, but not with insulin, LH, FSH, hCG, or prolactin (PRL). Three of the antisera neutralized relaxin-induced interpubic ligament formation in estrogen-primed mice in vivo. A new homologous cRlx RIA was developed through the use of rabbit antiserum 79888, synthetic cRlx for standards and 125l-labeled trace, and a goat anti-rabbit lgG-polyethylene glycol precipitant. The new RIA can be completed in 26 h and has a sensitivity of 0.195-0.39 ng cRlx/tube. Intra- and interassay coefficients of variation were 3% and 12.5%. During pregnancy in bitches, serum cRlx rose to about 10 micrograms/ml. Immunoactive cRlx was also detected in serum, colostrum, and milk of lactating bitches, but not in large volumes (100-300 microliters) of serum of pseudopregnant or estrous bitches. Immunoreactive cRlx was also found in seminal plasma, but not in serum, of male dogs. The new homologous cRlx RIA is simple, rapid, sensitive, and specific, and will be used in future studies of canine relaxin physiology.

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 effect of multifetal pregnancy reduction on serum relaxin

OBJECTIVE

To determine the effect of multifetal pregnancy reduction on circulating relaxin levels.

METHODS

Patients with multifetal pregnancies had relaxin levels determined on the day of multifetal pregnancy reduction, after the procedure, and late in pregnancy.

RESULTS

Forty-eight women (26 presenting with three fetuses and 22 with four or more) were studied. All pregnancies followed some form of ovulation induction. All pregnancies (except for one, which was reduced to a singleton) were reduced to twins. Pre-procedure, post-procedure and late-pregnancy relaxin levels were significantly higher in the in vitro fertilization (IVF)-gamete intrafallopian transfer (GIFT) group compared with the human menopausal gonadotropin (hMG)-alone group (P < .05). The initial number of fetuses had no significant effect on relaxin levels. Although post-procedure relaxin levels were significantly lower than pre-procedure levels (P = .002), relaxin levels continued to decrease throughout pregnancy, as evidenced by even lower levels later on (P = .0001).

CONCLUSIONS

Serum relaxin levels were significantly higher in the IVF-GIFT group than in the hMG-alone group, which probably reflects more aggressive ovulation induction in the former. Because relaxin levels continued to decrease throughout pregnancy, the difference observed between pre- and post-procedure levels are not considered to be due to the procedure itself.

Relaxin and its role in pregnancy

Relaxin is a 6000-d polypeptide, structurally related to insulin and the insulin-like growth factors. Unlike insulin, the structure of which is remarkably well conserved among the vertebrates, relaxin sequences can vary by more than 50% between different species. Despite these large sequence variations, relaxins (with few exceptions) have very similar biologic activities in animal test systems. The reason for this has recently come to light: the receptor binding region of the B chain, in contrast to the rest of the molecule, is highly conserved between species. Relaxin is measured by bioassays employing interpubic ligament formation in mice and guinea pigs, and by inhibition of uterine motility. A more sensitive and efficient bioassay is urgently needed. In women, the target organs for relaxin are the uterine cervix, myometrium, endometrium, and decidua. Other presumptive but unproven targets are the pubic symphysis and sacroiliac joints, mammary glands, and pituitary gland. Circulating relaxin is secreted by the corpus luteum. The placenta, decidua, or both also produce relaxin, which does not enter the circulation but may act in an autocrine or paracrine fashion. hCG is a stimulus to luteal relaxin secretion. Other regulatory factors are poorly defined. Aluteal women are hyporelaxinemic, and yet are capable of normal vaginal delivery of their infants. Local effects of placental or decidual relaxin cannot be discounted in such subjects. Hyperrelaxinemia may occur in women with multiple gestations and ovarian stimulation, and may be associated with increased premature births. Serum relaxin also is elevated in pregnant diabetics, but its role in this condition has not been defined. Clearly, further investigations are needed to delineate the precise role of relaxin in human pregnancy.

Transmission of relaxin from lactating bitches to their offspring via suckling

The 6-kDa polypeptide hormone relaxin (Rlx) has been identified in human and bovine milk, and we recently reported its presence in canine milk. We postulated that Rlx might be transferred via suckling to the newborn pups, where, by virtue of its known effects to increase the distensibility of the pelvic connective tissues, it could play a role in causing the excessive laxity of the capsule and ligaments of the coxofemoral joint that precedes the development of hip dysplasia in genetically predisposed animals. Rlx was found in the serum of dysplastic (HD+) bitches for up to 6 wk of lactation, whereas it was detected in the serum of nondysplastic (HD-) bitches for only 1-2 wk of lactation. Rlx concentrations in milk were up to 60-fold greater than in serum. Milk Rlx levels varied markedly, but were highest during the first week of lactation and decreased thereafter. There were no significant differences in milk Rlx concentrations between HD+ and HD- bitches. Although the source of Rlx in milk is unknown, it cannot be the ovary or uterus, since hystero-ovariectomy performed at the time of cesarean section did not eliminate Rlx from milk during subsequent lactation. In serum samples taken from newborn pups before suckling, there were significant quantities of Rlx, demonstrating that the hormone enters the fetus in utero. However, Rlx rapidly disappears from serum of pups prevented from suckling for five hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Relaxin secretion into human semen independent of gonadotropin stimulation

To investigate the control of relaxin (Rlx) secretion in men, we studied seminal plasma Rlx concentrations after physiologic and supraphysiologic gonadal stimulation. In the first experiment, 14 men with idiopathic hypogonadotropic hypogonadism provided semen samples at various time points before and during therapy with pulsatile GnRH. These data were compared to seminal plasma Rlx values in 5 normal men. In a second experiment, pharmacologic doses of hCG were administered in a fashion similar to that previously shown to have stimulated Rlx secretion from the CL of women. In men with idiopathic hypogonadotropic hypogonadism, no relationship was detected by linear regression analysis between seminal plasma Rlx and testosterone, testicular volume, ejaculate volume, or the appearance of sperm in the ejaculate. Rlx concentrations varied considerably between subjects (6-120 ng/ml) but remained fairly consistent within the same individual over time. Supraphysiologic gonadal stimulation with hCG similarly failed to alter seminal plasma Rlx (n = 5, mean +/- SEM; 48 +/- 9 ng/ml, 42 +/- 7 ng/ml, and 56 +/- 9 ng/ml on Days 1, 3, and 6, respectively; p < 0.05) in normal men despite dramatic increases in serum testosterone (763 +/- 25 ng/dl, 1702 +/- 136 ng/dl, and 1494 +/- 97 ng/dl on Days 1, 3, and 6, respectively; p < 0.05 vs. Day 1). Taken together, these data suggest that Rlx in men is secreted independently from direct gonadotropin control.

Elevated first-trimester serum relaxin concentrations in pregnant women following ovarian stimulation predict prematurity risk and preterm delivery

OBJECTIVE

To determine whether ovarian stimulation would result in higher circulating relaxin concentrations and whether this hyperrelaxinemia would be associated with prematurity.

METHODS

Two groups of women were studied: 1) women achieving pregnancy after ovarian stimulation (n = 114) and 2) women achieving pregnancy without treatment (n = 37). Serum was obtained at 6-12 weeks' gestational age; fetal number was determined by transvaginal ultrasound. Prematurity risk or preterm delivery was determined from the obstetric record. A specific human relaxin enzyme-linked immunosorbent assay was used to measure serum relaxin concentrations. Hyperrelaxinemia was defined as levels greater than 3 standard deviations above the weighted mean of levels in normal unstimulated singleton pregnancies at 6-12 weeks' gestation.

RESULTS

An association was found between prematurity risk or premature delivery and peripheral relaxin concentrations during weeks 6-12 of pregnancy in women having ovarian stimulation and in women having multiple gestations. Circulating relaxin concentrations greater than 16 ng/mL in women having ovarian stimulation and levels greater than 7 ng/mL in women who had multiple gestations predicted prematurity risk or premature delivery in 50% of the women.

CONCLUSIONS

These data demonstrate that after ovarian stimulation, some women have highly elevated circulating first-trimester relaxin concentrations. First-trimester hyperrelaxinemia identifies a group of women at risk for prematurity who can be monitored aggressively.

Human chorionic gonadotropin stimulation of relaxin secretion by luteinized human granulosa cells

OBJECTIVE

To determine the effect of human chorionic gonadotropin (hCG) on relaxin secretion by long-term cultures of luteinized human granulosa cells (GC).

DESIGN

Luteinized human GC were collected from 10 women undergoing in vitro fertilization (IVF) cycles. Luteinized human GC from each woman were plated in replicate wells at 1 x 10(5) cells/well and exposed to medium 199 (GIBCO, Grand Island, NY), medium 199 with 1 IU/mL hCG, and/or medium 199 with 100 IU hCG/mL. Luteinized human GC were maintained for up to 40 days in culture. Spent media were changed every 2 days and assayed for relaxin and progesterone (P) at the conclusion of each experiment.

SETTING

Tertiary care center.

PATIENTS, PARTICIPANTS

Luteinized human GC were obtained from women undergoing controlled ovarian hyperstimulation for IVF with one of the following regimens: (1) clomiphene citrate with human menopausal gonadotropins (hMG); (2) hMG alone; or (3) hMG with leuprolide acetate. All women were less than 40 years of age, in good health, and were not taking medications other than those used in the ovulation-induction regimen.

MAIN OUTCOME MEASURES

Levels of P and relaxin in spent media.

RESULTS

Relaxin secretion by luteinized human GC was dependent on hCG stimulation and was detected only after a time lag in culture. After relaxin secretion was detected, it was maintained throughout the culture period (10 to 22 days). Luteinized human GC produced P immediately under both basal and stimulated conditions. Progesterone production continued throughout the culture period with hCG-stimulated cells producing significantly greater P after 4 to 8 days in culture.

CONCLUSIONS

Luteinized human GC obtained at the time of oocyte retrieval secrete relaxin in response to hCG stimulation and secrete P under both basal and hCG-stimulated conditions, thereby serving as a model to explore luteal function and control.

Human seminal relaxin is a product of the same gene as human luteal relaxin

Unlike that of other species, which have only one gene encoding relaxin, the human genome contains two nonallelic genes for relaxin, designated H1 and H2, which encode markedly different relaxin peptides. Whereas human relaxin gene H2 is selectively expressed in the ovary, no ovarian expression of gene H1 has been detected. Since relaxin is actively produced in the human male, it is possible to postulate divergent gene expression of relaxin in the male and female. We examined this question directly through the structural determination of human seminal relaxin and its comparison with the structure of human luteal relaxin. Partially purified relaxin, prepared from pooled human seminal plasma which had been delipidated by extraction with acid acetone and hexane, subjected to two cycles of HPLC and an additional purification step by ion-exchange chromatography, was further purified by immunoaffinity chromatography, using a monoclonal antibody to the H2 relaxin A chain which cross-reacts with synthetic H1 relaxin, followed by an additional HPLC step performed on a C4 reverse-phase column. The recovered, purified relaxin was then analyzed by N-terminal gas-phase sequencing and fast atom bombardment mass spectroscopy for determination of the amino acid sequence and molecular ions of the A and B chains, respectively. The results demonstrate that the structure of the predominant relaxin in human semen plasma is derived from the product of the H2 gene, consisting of a N-terminal pyroglutamic acid A-24 A chain and a mixture of B-26 and B-27 B chains. With the exception of degradation of the seminal relaxin B chain C-terminus, this structure is identical to the structure of human luteal relaxin. Therefore, both human seminal and luteal relaxin are products of the H2 gene.

Ovarian expression of cellular Ki-ras p21 varies with physiological status

To elucidate the potential role of the ras protooncogene proteins in a specific tissue, the present study determined the levels of individual c-ras-encoded p21 proteins in the rat ovary during various stages of physiological function. p21 protein was extracted from ovaries taken from immature normal female rats, mature nonpregnant animals in the metestrus stage of the estrus cycle, rats at various stages of pregnancy, and actively lactating animals. Levels of individual p21s were evaluated by immunoblot analysis with specific antibodies to the p21 proteins encoded by the Kirsten, Harvey, and neuroblastoma c-ras protooncogenes, c-Ki-ras, c-Ha-ras, and N-ras. Results showed that c-Ki-ras p21 is at its lowest level in the immature ovary and increases with development of the corpora lutea to its highest levels at day 16 of pregnancy, after which levels decline and then rise again during lactation. This pattern, which mimics that of circulating progesterone levels, suggests that ovarian c-Ki-ras p21 levels are regulated and that c-Ki-ras p21 plays a role in the differentiated function of the rat ovary, likely the luteal compartment. In contrast, levels of c-N-ras p21 did not appear to vary with changes in the physiological function of the ovary but appeared to be constitutive. A preferential role for the c-Ki-ras p21 may be due to the documented unique differences in the structure of the carboxyl terminus of this particular c-ras p21.

Effects of endothelin and relaxin on rat uterine segment contractility

In order to determine the effects of endothelin (ET) and relaxin on uterine contractility, immature female rats were treated with estrogen (E, 1 microgram s.c., Days 1-3) or estrogen and progesterone (2 mg s.c. [E + P], Days 2 and 3), and killed; the uterine horns were removed and suspended in muscle baths. Initially, we determined the contractile response to varying doses of ET and how this response was altered by pretreatment with progesterone. Uterine strips from animals treated with E + P (n = 10) were less sensitive to the stimulatory effects of ET than were strips from E-treated animals (n = 10). This difference was significant at ET doses above 2.5 nM. After completion of the dose-response studies, contractile patterns in response to ET and relaxin were then studied in animals treated with E (n = 10) or E + P (n = 9). ET (5 nM) significantly increased uterine contractility, mostly through an effect on the frequency of contractions (p less than 0.01). Relaxin (25 ng/ml) decreased contractility, affecting all contractile parameters measured (p less than 0.01). ET stimulated contractility in uterine horn segments previously inhibited by relaxin (p less than 0.01), and relaxin reduced the increased contractility produced by earlier exposure to ET (p less than 0.01). These data indicate that ET and relaxin can interact reversibly to control contractility in uterine horn segments in vitro, and that progesterone pretreatment can diminish the contractile response to the stimulatory effects of ET.

Detection of Ki-ras proto-oncogene protein by a specific monoclonal antibody

We have used a commercially available mouse monoclonal antibody and shown it to bind specifically to cellular Ki-ras p21 proteins and not to cellular N- and Ha-ras p21 proteins. In conjunction with electrophoresis and Western blotting, this antibody can be used, with further detailing, to assess levels of the cellular Ki-ras p21 against a background of total p21s.

The role of estrogen and relaxin in the reproductive abnormalities of mice with Hertwig's anemia

Mice homozygous for a mutant allele (an/an) causing a lifelong macrocytic anemia (Hertwig's anemia) also demonstrate an inability to deliver their offspring, despite normal ovulation, conception, implantation, and fetal development. We investigated the roles of estrogen and relaxin in the etiology of the reproductive defect in the Hertwig's anemia mice. Immunoreactive relaxin levels were undetectable in the nonpregnant controls, whereas levels in both timed-pregnant controls and timed-pregnant affected mice were significantly higher than in nonpregnant controls, but not significantly different from each other. Mean interpubic ligament length in the pregnant Hertwig's anemia mice was significantly greater than that in nonpregnant controls, but significantly less than that in the pregnant controls on Day 18 of pregnancy. Porcine relaxin was administered to nonpregnant affected and unaffected littermates and to nonpregnant controls. Whereas controls showed a significant response to porcine relaxin, neither the Hertwig's anemia mice nor their unaffected littermates responded to the porcine relaxin. Additional study was performed to determine estradiol effects in the affected and control animals utilizing detailed computerized morphometric analysis of uterine horns and cervices from immature, estradiol-injected controls and Hertwig's anemia mice. Results demonstrated a statistically significant trophic effect of estradiol upon uterine horn and cervical enlargement, as assessed by weight and volume, in controls. Only a slight, non-significant effect was seen in Hertwig's anemia mice. Additional histological effects of estradiol, including endometrial enfolding observed in controls, were not present in Hertwig's anemia mice. Lack of response to both estrogen and relaxin is responsible for the parturitional defect in Hertwig's anemia mice.

Ovarian control of pituitary hormone secretion in early human pregnancy

To determine the influence of ovarian relaxin on the secretion of pituitary GH and PRL in vivo, we evaluated circulating serum hormone levels in 17 pregnant patients with functional corpora lutea (group I) and compared them to levels in 10 patients with premature ovarian failure (POF; group II) who became pregnant with egg donation and did not have corpora lutea. Group II patients had exogenous hormonal support. Serum relaxin (RLX), GH, PRL, estradiol (E2), and progesterone levels were measured weekly by RIA from weeks 4-8 of pregnancy. Analysis of variance and covariance were used to determine hormonal relationships. Serum RLX was present in the natural pregnancy group, with a mean of 1.94 micrograms/L over the study period. Serum RLX was undetectable in the POF patients (less than 0.16 micrograms/L). No significant difference in PRL or progesterone levels between the two groups was noted. E2 levels showed an upward trend in both groups with time and were significantly higher in patients of the POF group than in group I women (P = 0.001). GH levels were significantly higher in the natural cycle patients (P = 0.02) despite lower E2 levels. These data provide additional support for the concept that RLX production in early pregnancy originates from the corpus luteum. They suggest that a luteal product, probably RLX, stimulates GH secretion in early pregnancy. This is a previously undescribed role for RLX in pituitary physiology during human pregnancy.

Evidence for luteal cell hyperplasia during pregnancy

The pronounced increase in luteal size and weight that occurs during rat pregnancy has been largely attributed to luteal cell hypertrophy. It is generally believed that hyperplasia does not play a role in luteal growth, since it is thought that luteal cell division in vivo does not occur. Recent data suggest that this may not be the case. Thus, to determine whether luteal cell hyperplasia occurs during rat pregnancy, osmotic minipumps filled with 3H-thymidine were implanted in timed-pregnant rats on Day 6 or Day 11 of pregnancy. These pumps provided a continuous infusion of 10 microCi 3H-thymidine per hour for up to 7 days. Seven days later (Day 13 and Day 18 respectively), rats were killed, and the ovaries were removed and prepared for autoradiography. Labeled cells, which have the morphological characteristics of luteal cells, were clearly observed in autoradiographs of ovaries exposed to 3H-thymidine. The labeling index of these cells from ovaries exposed to 3H-thymidine on Days 6-13 of pregnancy was 6.0% and from ovaries exposed to 3H-thymidine on Days 11-18 of pregnancy was 1.2%. Whether the presence of labeled cells signifies proliferation of luteal cells or whether these cells are derived from another cell type that develops into cells morphologically similar to luteal cells is not known at present. However, regardless of origin, these data clearly demonstrate that the number of parenchymal cells in the corpus luteum does increase during pregnancy.

Diurnal variation of serum progesterone, but not relaxin, prolactin, or estradiol-17 beta in the pregnant bitch

The concentrations of progesterone (P), relaxin (Rlx), estradiol (E2) and PRL were measured by specific RIAs in serum samples collected twice daily at 8:00 am and 3:00 pm at weekly intervals after mating and until whelping in five Labrador Retriever bitches. From weeks 3 to 6 of pregnancy, P exhibited a conspicuous and statistically significant diurnal pattern (P less than 0.05), its serum concentration being approximately twice as high at 8:00 am as at 3:00 pm. A similar but nonsignificant trend was observed weeks 2, 7, and 8, and the overall ratio of the am/pm P concentrations was 2.4 +/- 0.28 (P less than 0.001). Rlx, E2, and PRL did not show a diurnal pattern at any time during pregnancy. The glandular sources and regulation of secretion of Rlx were further investigated. Rlx bioactivity was detected in canine placentas and ovaries, providing supportive evidence that these organs may be a dual source of the hormone in canine pregnancy. Injection of ovine PRL in three pseudopregnant bitches significantly increased serum P concentration as compared with seven untreated pseudopregnant controls, but Rlx was not detectable in serum before, during or after PRL treatment. The data support the view that Rlx and P are independently regulated in the bitch; PRL may be a regulator of P, but not of Rlx secretion. However, as PRL showed no diurnal changes in concentration, it does not appear to be directly responsible for the diurnal pattern exhibited by P.

Human chorionic gonadotropin and relaxin concentrations in early ectopic and normal pregnancies

The present study was performed to investigate whether determination of serum relaxin concentrations would allow assessment of the gestation further than that provided by determination of hCG. Serum relaxin concentrations were quantified in women with resorbing ectopic gestations (as documented by declining titers of beta-hCG). The control group consisted of individuals with intrauterine pregnancies. As an additional control, we studied pregnancies conceived through ovulation induction, which usually have an increased volume of relaxin-secreting luteal tissue. On days 39-70 of gestation, the mean serum relaxin concentrations were significantly lower in ten resorbing ectopic gestations (P less than .001, permutation test) than in the normal control group of 13 intrauterine pregnancies. The median serum relaxin concentrations in patients who had ovulation induction with Pergonal were substantially higher than the median for all normal controls; values in clomiphene citrate-treated patients were within the normal range. These data suggest that relaxin secretion correlates with luteal function in both normal and abnormal gestations and reflects the status of the pregnancy. Thus, relaxin may serve as a useful clinical marker.

The antagonistic effect of oxytocin and relaxin on rat uterine segment contractility

To test the interaction of various hormones on the myometrium, the following experiments were done studying in vitro contractile activity of uterine segments from immature rats. The rats were divided into two groups: group 1 animals were treated with estrogen (n = 9) and group 2 animals were treated with both estrogen and progesterone (n = 11). Uteri from animals in each group were removed and segments were maintained in a temperature- and pH-controlled organ bath. After baseline contractions were established, uterine segments were treated with either oxytocin and then relaxin, or relaxin and then oxytocin. The dose of relaxin used, 20 ng/ml, was previously shown to be effective in inhibiting uterine contractions of animals treated with either estrogen or estrogen plus progesterone. The dose of oxytocin, 2.5 mlU/ml, was the maximal effective dose shown not to produce prolonged tetany. Estrogen plus progesterone treatment increased the frequency of contractions and resulted in contractions of greater duration of the maximal contractile force, as compared with treatment with estrogen alone. Oxytocin caused a stimulation of contractions in relaxin-inhibited uterine strips. Relaxin decreased the hypertonic contractions produced by oxytocin treatment, resulting in contractions similar to baseline. These data demonstrate that oxytocin and relaxin are directly antagonistic in their effects on uterine contractility. This suggests that labor may occur as a result of increased sensitivity to oxytocin or a decreased sensitivity to relaxin.

Human corpus luteum secretion of relaxin, oxytocin, and progesterone

To determine whether the human corpus luteum is a source of relaxin and oxytocin, we measured the concentrations of these peptides in plasma obtained from the ovarian veins of ovaries with and without a corpus luteum and compared these to peripheral plasma levels. Peripheral and ovarian venous blood samples were obtained from 34 nonpregnant women, 13 during the luteal phase and 21 during the follicular phase of their cycles, and from a 6-week pregnant woman. Plasma relaxin, oxytocin, and progesterone concentrations were determined by sensitive and specific RIAs. Plasma relaxin levels were not detectable (less than 0.16 microgram/L) in peripheral or ovarian venous plasma not draining a corpus luteum. The mean relaxin concentration in plasma draining an ovary with a corpus luteum was 0.41 +/- 0.09 (+/- SE) microgram/L. Oxytocin levels also were significantly higher in plasma draining an ovary with a corpus luteum (6.70 +/- 1.86 pmol/L) than in that draining the ovary with no corpus luteum (1.58 +/- 0.09 pmol/L; P less than 0.01) or in peripheral plasma (1.58 +/- 0.09 pmol/L; P less than 0.025). The mean progesterone concentration also was highest in plasma draining an ovary with a corpus luteum (210.2 +/- 50.5 nmol/L) compared with those in plasma from the contralateral ovarian vein (40.3 +/- 16.5 nmol/L P less than 0.005) and peripheral plasma (30.2 +/- 5.7 nmol/L; P less than 0.005) during the luteal phase. In a woman who was 6 weeks pregnant, plasma draining the ovary with a corpus luteum had 1.9 micrograms relaxin/L, but only 0.49 pmol/L oxytocin; the latter was similar to concentrations in noncorpus luteum-bearing ovarian venous plasma. These findings indicate that the human corpus luteum secretes relaxin, oxytocin, and progesterone. Both ovarian oxytocin and relaxin may function as paracrine or autocrine modulators of luteal function.

Serum relaxin and progesterone concentrations in pregnant, pseudopregnant, and ovariectomized, progestin-treated pregnant bitches: detection of relaxin as a marker of pregnancy

Serum concentrations of relaxin and progesterone were measured by specific radioimmunoassays in pregnant, pseudopregnant, or ovariectomized (between gestation weeks 4 and 5) pregnant Labrador Retriever bitches. Daily administration of 17 alpha-ethyl-19-nortestosterone was performed to maintain gestation in the ovariectomized pregnant bitches. This synthetic gestagen was selected because it did not interfere with the assay for endogenously secreted progesterone concentration in serum. Serum progesterone concentration was high in ovarian-intact pregnant or pseudopregnant bitches, but the mean progesterone concentration in pseudopregnant bitches (evaluated at 4 weeks after mating) was only 56% of the concentration in pregnant bitches. After ovariectomy, serum progesterone concentration decreased to undetectable values. Unlike progesterone, serum relaxin concentration increased during the latter half of pregnancy in the ovarian-intact and in the ovariectomized pregnant bitches, but relaxin was not detectable at any time in the pseudopregnant bitches. The amount of relaxin measured in the ovariectomized pregnant bitches was less (P less than 0.05) than that in ovarian-intact bitches, suggesting that the ovaries may have contributed to the total circulating relaxin concentration in the latter. Placental production of relaxin might have accounted for the serum relaxin concentration after ovariectomy; thus, the ovary and placenta each may secrete relaxin during gestation in bitches. Regardless of its source, measurement of serum relaxin concentration may offer a useful way of distinction between pregnancy and pseudopregnancy in dogs.

Synergistic effect of relaxin and progesterone on cyclic adenosine 3',5'-monophosphate levels in the rat uterus

Cyclic adenosine 3',5'-monophosphate is known to modulate smooth muscle contractility. Because both relaxin and progesterone have been demonstrated to affect myometrial cyclic adenosine monophosphate activity, we questioned whether the previously observed synergism of these two hormones in inhibiting uterine contractility is mediated via cyclic adenosine monophosphate. Immature rats were treated with estradiol benzoate (n = 7) or a combination of estradiol benzoate and progesterone (n = 7). Uterine horns were isolated, each horn was divided into two segments, and these horn segments were incubated in Ringer-Locke solution, either alone (control) or with 3-isobutyl-1-methylxanthine (MIX) 0.5 mM, MIX 0.5 mM + relaxin 10 ng/ml, or MIX 0.5 mM + relaxin 50 ng/ml. When compared with uterine segments incubated in MIX alone, treatment with MIX + relaxin 50 ng/ml significantly increased cyclic adenosine monophosphate levels in animals treated with estradiol benzoate alone or in combination with progesterone. Relaxin 10 ng/ml was sufficient to significantly elevate mean (+/- SEM) uterine cyclic adenosine monophosphate levels above that of control MIX-treated uteri in animals receiving both estradiol benzoate and progesterone (2.49 +/- 0.39 pm/micrograms deoxyribonucleic acid [DNA] versus 1.08 +/- 0.16 pm/microgram DNA, p less than 0.05) but not in animals receiving estradiol benzoate alone (2.08 +/- 0.32 pm/micrograms DNA versus 1.28 +/- 0.16 pm/micrograms DNA, NS). Compared with treatment with MIX only, MIX + relaxin 10 ng/ml and MIX + relaxin 50 ng/ml produced greater increases in uterine cyclic adenosine monophosphate in the steroid combination group than in the estradiol benzoate controls (144.8% and 233.7% versus 71.7% and 156.6%, respectively). These results suggest that the synergism of relaxin and progesterone in inhibiting uterine contractility may be mediated by intracellular cyclic adenosine monophosphate.

The effect of relaxin on calcium fluxes in the rat uterus

Relaxin is a polypeptide hormone that inhibits rat uterine contractions. To test the hypothesis that the mechanism of action of this effect may involve shifts in calcium ions, the biologic action of relaxin on isolated rat uterine horns was directly correlated with measurements of 45Ca2+ efflux from and uptake into the tissues. Kinetic analysis demonstrated that the efflux of 45Ca2+ from rat uterine horns was significantly faster when tissue was incubated with 25 ng/ml relaxin as compared with control tissues incubated with no relaxin. In addition, at the end of the efflux experiments, control uteri contained 3.9% of the starting 45Ca2+, whereas the relaxin-treated uteri contained only 2.55%, indicating greater total Ca2+ efflux from the relaxin-treated horns (p less than 0.05). The effect of relaxin on 45Ca2+ uptake by uterine tissue was also studied. Analysis of uptake curves by linear regression demonstrated that relaxin treatment leads to less total uptake of 45Ca2+ in the uterine tissue, although the differences are not statistically significant. These experiments demonstrate that relaxin inhibition of rat uterine contractions in vitro is associated with a decrease in intracellular free Ca2+, caused, at least in part, by the promotion of Ca2+ efflux. These results represent the first step in defining the mechanism of action of this hormone.

Peripheral relaxin levels during pregnancy in a woman with homozygous familial hypobetalipoproteinemia

A case of a normal pregnancy conceived spontaneously in a 22-year-old woman with hypobetalipoproteinemia evidenced peripheral levels of relaxin in the range of uncomplicated singleton pregnancies in conjunction with low peripheral levels of progesterone. The establishment and maintenance of uterine quiescence in this hypoprogestational pregnancy may be attributable to these "normal" relaxin concentrations or to local uterine factors, including decidual relaxin production, which would not be reflected in circulating relaxin levels.

The source of relaxin in pregnant Syrian hamsters

Serum immunoreactive relaxin (IR) was measured on days 8, 10, and 14 of gestation in intact and ovariectomized (day 8 of pregnancy) hamsters. In intact hamsters, IR increased from 3-4 ng/ml on day 8 to 20 ng/ml by day 14 of pregnancy. After ovariectomy on day 8, pregnancy failed, and IR decreased rapidly to 0.29 ng/ml on day 14. However, when pregnancy was maintained in ovariectomized hamsters by daily injections of 0.1 microgram 17 beta-estradiol and 4 mg progesterone, serum IR rose to levels similar to those in intact hamsters on days 10 and 14 of pregnancy (i.e. 15 and 20 ng/ml, respectively). Placentas were obtained from other groups of hamsters on days 11, 14, and 15 of pregnancy and homogenized for bioassay by the classical guinea pig pubic symphysis palpation bioassay. Homogenates of placentas obtained on days 14 and 15 contained, respectively, 4 and 10 micrograms eq porcine relaxin/serum relaxin/g fresh tissue. The placenta, rather than the ovary, appears to be the source of during pregnancy in the hamster.

Plasma relaxin levels in pregnant and lactating dogs

The pattern of plasma relaxin has been studied during pregnancy and following parturition in two breeds of dogs, Labrador retrievers and beagle hounds. Blood samples were collected at weekly intervals following mating and during pregnancy, parturition, and lactation. Relaxin, progesterone, and estradiol-17 beta were determined by specific double antibody radioimmunoassays. Immunoreactive relaxin (IR) was not detectable in plasma of male dogs, bitches in anestrous, or pseudopregnant bitches that had undergone an infertile mating. IR was first detectable in plasma in the third or fourth week of gestation in retrievers and beagles. IR levels rose to a peak of 4-5 ng/ml in both breeds. The peak plasma levels were reached 2-3 wk before whelping and declined significantly prior to that event. IR then persisted during lactation at a level of 0.5-2 ng/ml for 4-9 wk, but was significantly higher (p less than 0.01) at all time periods and persisted longer in labradors than in beagles. The secretion of relaxin did not parallel that of progesterone, which was highly elevated in the first samples drawn (during the first week of pregnancy), remained high through 5 or 6 wk of gestation, then slowly declined until the time of parturition, becoming undetectable during lactation. Plasma estradiol-17 beta was low after the second week of pregnancy in both breeds of dogs and became undetectable during lactation. The source of relaxin in the dog is not known currently, and its sites of secretion and role in pregnancy are currently under investigation in our laboratories. The dog is the first species in which plasma IR is detectable during lactation using antibody R6.(ABSTRACT TRUNCATED AT 250 WORDS)

Human semen relaxin and its correlation with the parameters of semen analysis

The relaxin content of 92 normal semen samples and 85 semen samples selected at random was correlated to the parameters measured on routine semen analysis in those samples. The concentration of immunoactive relaxin in a sample of semen plasma did not correlate with any of the parameters commonly used for semen analysis: count, percent motility, grade of forward progression, volume, and morphology.

The effect of relaxin and prostaglandin E2 on the motility of human spermatozoa

Relaxin and prostaglandin E2 (PGE2) are present in human semen and have been shown to affect sperm motility. The authors further examined the effects of porcine relaxin and PGE2 on the motility of human spermatozoa. A dose-response study revealed that PGE2 at a concentration of 25 micrograms/ml is most effective in improving the motility of washed human sperm. Relaxin (100 ng/ml), PGE2 (25 micrograms/ml), or the two combined have no effect on the motility of spermatozoa in fresh, normal semen, suggesting that the constituents of fresh semen are optimal for motility. Relaxin and PGE2 individually improve the motility of washed spermatozoa. However, relaxin, but not PGE2, improves the motility of sperm in semen incubated at 37 degrees C for 5 hours (aged). In contrast to the individual substances, a combination of relaxin + PGE2 has no effect on the motility of washed spermatozoa or aged spermatozoa, suggesting that these two substances antagonize each other's actions on sperm motility. The presence of both relaxin and PGE2 in seminal plasma with normal motility spermatozoa suggests that other factors in seminal plasma regulate the effects of these substances on sperm motility.

Effect of relaxin on human spermatozoa

To study its effect on the motility of human spermatozoa, relaxin was added at different concentrations to human semen samples of various qualities as well as to washed spermatozoa. Relaxin in physiologic concentrations (10-100 ng/mL) had no significant effect on sperm motility in normal semen samples. However, the addition of relaxin to semen samples with low sperm motility significantly increased the motility. Addition of relaxin similarly increased the motility of spermatozoa from normal semen samples that were either aged or washed; the treatment resulted in a decrease in motility. When sperm motility was optimal, as in normal samples, addition of relaxin did not increase motility. However, in some situations of decreased motility, addition of relaxin resulted in improvement of spermatozoan motility. Relaxin may have clinical value in the treatment of male infertility.

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.

The use of voided urine temperature in the determination of basal body temperature

The temperature of freshly voided urine has been shown to be a reliable predictor of body temperature. This relationship was confirmed for the measurement of BBT. A method was described for patients to obtain their BBT in a way that they may find more convenient than obtaining either oral or rectal temperature. The BBT graph patterns generated from the temperature of freshly voided urine closely paralleled those generated by oral temperature.

The effect of relaxin on the motility of sperm in freshly thawed human semen

In an attempt to improve the motility of thawed spermatozoa after 1 week of its being frozen, we treated ten normal semen samples with 16.7 nmol relaxin and 6 mmol caffeine. Motility and grade of forward progression were examined after thawing. Caffeine significantly improved motility of spermatozoa. Relaxin, when added to semen at the time of thawing, improved motility and grade of forward progression significantly. This effect was not seen if relaxin was added before freezing. These results suggest that the biologic activity of relaxin is adversely affected by freezing and thawing in seminal plasma. These observations may have clinical importance for the improvement of motility of frozen spermatozoan samples at the time of artificial insemination and for the possible improvement of pregnancy rates.

The role of prolactin in the regulation of the primate corpus luteum

The role of PRL in the control of corpus luteum (CL) function was examined in hyperprolactinemic and euprolactinemic female rhesus monkeys with hypothalamic lesions in which ovulatory menstrual cycles were induced by the pulsatile administration of GnRH, in intact postpartum monkeys nursing their infants, as well as in animals treated with bromocriptine. In the lesioned monkeys, neither markedly elevated nor undetectable (bromocriptine-suppressed) PRL levels influenced the time courses of postovulatory plasma progesterone concentrations compared to those in monkeys with normal PRL concentrations. Plasma progesterone concentrations in the hyperprolactinemic monkeys, however, did not decline to undetectable levels at the end of the luteal phase, as is the case in normal animals, but remained slightly elevated for extended periods, a pattern characteristic of lactating animals. In both lesioned and postpartum animals, bromocriptine administration or removal of suckling infants from the latter resulted in complete functional luteolysis. These observations suggest that PRL does not play a significant role in the control of the CL of the menstrual cycle, but that in high concentrations, this hormone can partially maintain previously established CL.

Steroid effects on relaxin secretion in the rat

These studies were performed to determine if estrogen and/or androgens are involved in the regulation of relaxin secretion in the pregnant rat. Animals were hysterectomized at Day 15 of pregnancy and either untreated or given a) a subcutaneous Silastic capsule containing crystalline testosterone, b) a subcutaneous Silastic capsule containing crystalline dihydrotestosterone, or c) daily subcutaneous injections of 100 micrograms estradiol. A group of sham-operated animals served as controls. Serum samples taken at Days 14, 16, and 18 of pregnancy were assayed for relaxin and progesterone. Treatment with either estradiol or testosterone attenuated the decline in serum relaxin and progesterone concentrations observed following hysterectomy, whereas dihydrotestosterone (a nonaromatizable androgen) had no effect upon either relaxin or progesterone levels. These results suggest that estradiol and testosterone, previously implicated in the control of luteal progesterone production, also stimulate luteal relaxin secretion. The mechanism by which testosterone stimulates relaxin secretion is probably via its aromatization to estradiol within the corpus luteum.

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.

Hormone secretion by monolayer cultures of human luteal cells

To be able to study the control mechanisms for human luteal function, a system was designed to maintain human luteal cells in culture. Collagenase dispersed cells of human corpora lutea of the menstrual cycle and pregnancy were maintained as monolayer cultures for 26 days. Progesterone (P) and relaxin (R) in culture media were measured by radioimmunoassay. Both menstrual cycle and pregnancy luteal cells secreted P for 26 days. hCG increased P secretion by menstrual cycle luteal cells, but not by pregnancy luteal cells. R was not detected in media of menstrual cycle luteal cell controls, nor in media of cells incubated with hCG. R was detected in media of pregnancy luteal cells for 6 days. Addition of hCG caused a significant increase in media R levels only on day 2 of culture. These studies show that human luteal cells can be maintained as viable monolayer cultures for at least 26 days and these cultures can be used to study control of human luteal function.

Placental control of ovarian immunoreactive relaxin secretion in the pregnant rat

To investigate the control mechanisms for the secretion of relaxin in pregnant rats, the effects of the fetus, placenta, and uterus were studied. Plasma immunoreactive relaxin and progesterone were measured in pregnant rats, from days 8--1 post partum. On day 16 of pregnancy, groups of animals were subjected to removal of the fetuses, conceptuses (fetuses and placentae), or uteri. To determine whether there are extraovarian sources of circulating relaxin, a group of pregnant rats was ovariectomized on day 16. Immunoreactive relaxin was undetectable in the plasma of pregnant rats before day 10, and increased to a mean concentration of 0.52 +/- 0.01 (SEM) ng/ml on day 13. In control animals, immunoreactive relaxin levels remained at about this concentration throughout the remainder of pregnancy and declined rapidly post partum. The pattern of secretion of relaxin in fetectomized animals was similar to that in controls. In contrast, a significant decline in immunoreactive relaxin was seen, within 24 h after surgery, in those animals in which removal of the conceptuses or hysterectomy was performed. In these animals, immunoreactive relaxin was undetectable within 48 h after surgery and remained undetectable throughout the experimental period. In animals that were ovariectomized, immunoreactive relaxin was undetectable 24 h after surgery. Progesterone secretion in animals that had fetectomy or removal of the conceptuses performed was similar to that in controls. These groups showed a significant decline in progesterone on day 17 of pregnancy, and progesterone continued to decline until day 1 post partum. Progesterone in hysterectomized animals declined more abruptly than in either controls or other experimental groups. Ovariectomy resulted in a prompt fall in plasma progesterone. These results indicate that in the rat, the fetus is not needed for the maintenance of relaxin secretion throughout pregnancy, the placenta controls the ovarian secretion of relaxin. The uterus does not exert a tropic effect upon relaxin secretion, no extraovarian sources of circulating relaxin exist in the rat, and there is a divergence between progesterone and relaxin secretion during rat pregnancy.

Serial relaxin concentrations in human pregnancy

Relaxin is a peptide hormone produced by the corpus luteum during pregnancy in human beings. There are no extraluteal sites of production of relaxin in women. By means of a heterologous porcine radioimmunoassay, serial serum relaxin concentrations were determined in three women throughout pregnancy and into labor. All three demonstrated a first-trimester elevation followed by a second-trimester decline; values then remained stable throughout the second and third trimesters and into labor. This further confirms the functional activity of the corpus luteum throughout pregnancy and the value of relaxin as an index of luteal function during gestation.