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

Signaling Pathways Regulating Human Cervical Ripening in Preterm and Term Delivery

At the end of gestation, the cervical tissue changes profoundly. As a result of these changes, the uterine cervix becomes soft and vulnerable to dilation. The process occurring in the cervical tissue can be described as cervical ripening. The ripening is a process derivative of enzymatic breakdown and inflammatory response. Therefore, it is apparent that cervical remodeling is a derivative of the reactions mediated by multiple factors such as hormones, prostaglandins, nitric oxide, and inflammatory cytokines. However, despite the research carried out over the years, the cellular pathways responsible for regulating this process are still poorly understood. A comprehensive understanding of the entire process of cervical ripening seems crucial in the context of labor induction. Greater knowledge could provide us with the means to help women who suffer from dysfunctional labor. The overall objective of this review is to present the current understanding of cervical ripening in terms of molecular regulation and cell signaling.

Co-option and evolution of non-olfactory proteinaceous pheromones in a terrestrial lungless salamander

Gene co-option is a major force in the evolution of novel biological functions. In plethodontid salamanders, males deliver proteinaceous courtship pheromones to the female olfactory system or transdermally to the bloodstream. Molecular studies identified three families of highly duplicated, rapidly evolving pheromones (PRF, PMF, and SPF). Analyses for Plethodon salamanders revealed pheromone mixtures of primarily PRF and PMF. The current study demonstrates that in Desmognathus ocoee--a plesiomorphic species with transdermal delivery--SPF is the major pheromone component representing >30% of total protein. Chromatographic profiles of D. ocoee pheromones were consistent from May through October. LC/MS-MS analysis suggested uniform SPF isoform expression between individual male D. ocoee. A gene ancestry for SPF with the Three-Finger Protein superfamily was supported by intron-exon boundaries, but not by the disulfide bonding pattern. Further analysis of the pheromone mixture revealed paralogs to peptide hormones that contained mutations in receptor binding regions, such that these novel molecules may alter female physiology by acting as hormone agonists/antagonists. Cumulatively, gene co-option, duplication, and neofunctionalization have permitted recruitment of additional gene families for pheromone activity. Such independent co-option events may be playing a key role in salamander speciation by altering male traits that influence reproductive success.

Endocrinology of parturition

The myometrium must remain relatively quiescent during pregnancy to accommodate growth and development of the feto-placental unit, and then must transform into a highly coordinated, strongly contracting organ at the time of labour for successful expulsion of the new born. The control of timing of labour is complex involving interactions between mother, fetus and the placenta. The timely onset of labour and delivery is an important determinant of perinatal outcome. Both preterm birth (delivery before 37 week of gestation) and post term pregnancy (pregnancy continuing beyond 42 weeks) are both associated with a significant increase in perinatal morbidity and mortality. There are multiple paracrine/autocrine events, fetal hormonal changes and overlapping maternal/fetal control mechanisms for the triggering of parturition in women. Our current article reviews the mechanisms for uterine distension and reduced contractions during pregnancy and the parturition cascade responsible for the timely and spontaneous onset of labour at term. It also discusses the mechanisms of preterm labour and post term pregnancy and the clinical implications thereof.

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

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

Recombinant human relaxin as a cervical ripening agent

OBJECTIVE

The aim of this study was to investigate the efficacy and safety of recombinant human relaxin (rhRIx) as a cervical ripening agent in women with an unfavourable cervix before induction of labour at term.

DESIGN

A multi-centre, double-blind, placebo-controlled trial performed in Edinburgh, Glasgow and Oxford. Women were treated with 0, 1, 2 or 4 mg of rhRIx in a gel vehicle administered intravaginally. Analysis of variance tests were performed on all continuous variables, and Cochran Mantel-Haenszel tests employed for all discrete variables.

PARTICIPANTS

Ninety-six women at 37 to 42 weeks of gestation with a singleton pregnancy and a modified Bishop score of < or = 4 were recruited.

RESULTS

There was no significant difference in the change in modified Bishop score between the four treatment groups. The lengths of the first and second stages of labour were similar in all 4 groups. PGE2 and oxytocin requirements were similar in all groups, as was the mode of delivery. There was no evidence that relaxin was absorbed systemically when given in this way.

CONCLUSION

Recombinant human relaxin 1 to 4 mg, administered as an intravaginal gel, has no effect as a cervical ripening agent before induction of labour at term.

Effect of leuprolide acetate in patients with functional bowel disease. Long-term follow-up after double-blind, placebo-controlled study

We initially investigated the effects of a gonadotropin-releasing hormone analog, leuprolide acetate, in 28 patients with moderate to severe functional bowel disease in a phase-II, randomized, double-blind, and placebo-controlled study using Lupron Depot 3.75 mg (which delivers a continuous low dose of drug for one month) or placebo given intramuscularly. After completing that 12-week study period during which their symptoms had improved significantly (P < 0.01-0.5), the 28 patients were allowed to continue receiving leuprolide acetate; they were monitored for an additional 40 weeks. Of those 28, 25 (89%) finished the 52-week treatment. Drug administration was changed from the monthly low-dose form of leuprolide acetate to a daily subcutaneous dose that was gradually increased from 0.5 mg daily to an effective therapeutic dose (1.0-1.5 mg). All subjects received estrogen replacement during this period. Continued use of leuprolide acetate at maximum therapeutic dosage and over longer periods of time produced even more striking and significant changes in the disabling and debilitating symptoms of functional bowel disease. Nausea, abdominal pain, early satiety, anorexia, and abdominal distension decreased markedly (P < 0.0001) and vomiting was also reduced (P < 0.01) more than in the short-term, low-dosage, double-blind study. Combined total symptom scores and overall assessment also changed significantly in the long-term phase (both P < 0.0001).

Effects of porcine relaxin on contraction, membrane response and cyclic AMP content in rat myometrium in comparison with the effects of isoprenaline and forskolin

1. The longitudinal muscle from the uterus of oestrogen-treated rats was quiescent in Mg-free Krebs solution. Electrical stimulation generated phasic contraction, which was depressed to 35% and 18% by 50 mu and 150 mu porcine relaxin, respectively. 2. The phasic contractions were more strongly depressed to 26% by 50 mu relaxin in solution containing 0.6 mM Mg, and the depression lasted for more than 4 h after the removal of relaxin. During the persisting depression, raising the external Ca to 7.5 mM did not restore the contraction, but the contraction was restored by removal of Mg. 3. The depression of the phasic contraction by relaxin, examined in Mg-free solution, was enhanced and reduced by pretreatment of the tissue with 0.6 mM Mg and 0.6 mM Mn, respectively, for about 15 min. In contrast, the depression of contraction by isoprenaline or forskolin was enhanced by pretreatment with either Mg or Mn. 4. The cellular content of cyclic AMP was measured in Krebs solution containing 0.6 mM Mg. The values were 1.24 (pmol mg-1 protein) in control solution, and 2.31 and 1.56 when the tissues were treated with 150 mu relaxin and 10(-9) M isoprenaline, respectively. 5. The cyclic AMP production in response to 10(-7) M forskolin measured in Mg-free solution was enhanced when the tissue was pretreated with either 0.6 mM Mg or Mn for 15 min. The cyclic AMP production in response to 100 mu relaxin was increased when the tissue was pretreated with 0.6 mM Mg, and was unchanged by pretreatment with Mn. The cyclic AMP production in response to 10(-9) M isoprenaline was unchanged by pretreatment with the divalent cations. 6. The membrane potential of the muscle was -60.8 mV in Krebs solution containing 0.3 mM Mg, and electrical stimulation induced an action potential which consisted of spike and plateau components. Application of 150 mu relaxin reduced the duration of the plateau; the contractions were progressively depressed. The resting membrane potential and membrane resistance were unchanged by application of 150 mu relaxin. The membrane was hyperpolarized by 2.8 mV, accompanied by a decrease in membrane resistance, when 10(-9) M isoprenaline was applied. 7. Although there were several differences between the effects of relaxin and isoprenaline, it is probable that some process, which is cyclic AMP-dependent, accelerated by Mg and depressed by Mn, is involved in the depressant action of relaxin on contraction.

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.

Antenatal serum levels of relaxin in patients having preterm labour

This study is the first report of antenatal levels of relaxin measured by homologous radioimmunoassay in peripheral serum from patients who subsequently had a preterm delivery. Serial blood samples were collected antenatally from a group of subjects known to be at increased risk of preterm labour because of a past history of shortened pregnancy. Serum relaxin was measured using an homologous radioimmunoassay based on a synthetic bioactive analogue of the native hormone. In women whose pregnancies ended preterm most measurements were within the range of values previously established in normal antenatal patients although some measurements early in pregnancy were above the normal range. These findings suggest that low serum levels of relaxin are not causatively related to the onset of labour before term.

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

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

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

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

Relaxin inhibits the plateau component of the action potential in the circular myometrium of the rat

The effects of relaxin on contractility and membrane potential of the longitudinal and circular smooth muscle layers of the uterus have been studied in vitro using oestrogen-treated, non-pregnant rats and pregnant rats. Relaxin decreased the amplitude of contractions induced by electrical stimulation of longitudinal myometrium by decreasing the duration of the bursts of action potentials. This effect was transient and tachyphylaxis always developed and was observed following injection of steroids and up to day 17 of pregnancy. There was no inhibition of tissues from rats from day 18 of pregnancy to term. The peptide had no effect on resting membrane potential, space constant or time constant. Action potentials recorded from circular myometrium of non-pregnant rats pre-treated with oestrogen consisted of an initial spike or short burst of spikes followed by a prolonged plateau of depolarization. Spontaneous action potentials and associated contractions were abolished within 2 min of exposure to relaxin (10(-8) g/ml) while contractions of much smaller amplitude could be evoked with depolarizing current pulses. This effect was associated with depression of the plateau component of the action potential whereas the spike component was left intact. Relaxin had no effect on passive membrane properties. The action potentials of circular myometrium of rats up to day 21 of pregnancy were qualitatively similar to those recorded in the same muscle layer from oestrogen-treated, non-pregnant rats and the plateau component was also blocked by relaxin in these tissues. Bursts of spikes were observed in circular strips 24-36 h before parturition, and the effect of the peptide on these was a transient inhibition similar to that observed in longitudinal myometrium. Oxytocin increased the amplitude of the spike and the amplitude and duration of the plateau. Relaxin abolished the plateau in the presence of 10(-11) and 10(-10) M-oxytocin but was ineffective when the concentration of the spasmogen was increased further. Prostaglandin F2 alpha increased the amplitude and duration of the plateau. Relaxin abolished the responses to 10(-10) and 10(-9) M-prostaglandin F2 alpha. The results of this study demonstrate that relaxin specifically inhibits contractions in the circular layer of the myometrium by abolishing the plateau component of the action potential. This action appears to be different from that of other smooth muscle relaxants tested in these experiments (isoprenaline, papaverine and verapamil). All of these abolished simultaneously both the spike and plateau components of the action potential.

The effect of in vivo progesterone administration on relaxin-inhibited rat uterine contractions

Progesterone pretreatment in vitro was previously shown to sensitize myometrium to the inhibiting effect of relaxin. The following experiments were performed to control for possible artifacts of the in vitro system and to place these studies on a more physiologic basis. Immature rats were treated with estrogen and either progesterone or vehicle only. Uterine horn segments were isolated and mounted in a muscle bath. After a baseline contraction pattern was established by means of electrical stimulation, porcine relaxin was added to the bath. At all dose levels of relaxin, greater inhibition of contraction amplitude occurred in uterine segments of progesterone-treated animals. Since both progesterone and relaxin are present in the circulation from the time of the missed menses in human pregnancy, this interaction suggests a physiologic synergism in the maintenance of early human pregnancy.

Synergistic effect of human relaxin and progesterone on human myometrial contractions

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

Relaxin--a review

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