The protective effects of ritodrine against hypoxia/reoxygenation-induced injury in endometrial stromal cells.

Endometriosis (EMS) is often observed in women of childbearing age and significantly impacts patients' quality of life. Ritodrine is a ß2 receptor agonist applied for relaxing the uterine smooth muscle. Its inhibitory effects on inflammation have recently been noted. The present study explored the protective impact of Ritodrine on hypoxia/reoxygenation (H/R)- induced injury in endometrial stromal cells (ESCs). Human ESCs (HESCs) were treated with Ritodrine (0.1, 0.5 µM) for 24 h, followed by exposure to H/R for 6 h. Ritodrine ameliorated H/R-induced higher reactive oxygen species (ROS), declined glutathione (GSH) concentration and increased production of tumor necrosis factor-α (TNF-α), interleukin- 6 (IL-6), and monocyte chemotactic protein 1 (MCP-1) in HESCs. Furthermore, Ritodrine ameliorated the H/R-induced higher nuclear level of nuclear factor κ-B (NF-κB) p65 expression and increased luciferase activity of the NF-κB promoter. In addition, we show that Ritodrine mitigated H/R-induced higher estrogen receptor α (ER-α) expression in HESCs. Interestingly, overexpressing ER-α abolished the regulatory effects of Ritodrine on oxidative stress and the NF-κB pathway-mediated inflammation. Collectively, our data reveal that Ritodrine alleviated H/R-induced injury in ESCs by inhibiting the ER-α/NF-κB pathway.

Atosiban Combined with Ritodrine for Late Threatened Abortion or Threatened Premature Labor Patients with No Response to Ritodrine: A Clinical Trial.

BACKGROUND Premature labor is an important cause of infant death and long-term disability. This study aimed to explore the safety and effectiveness of combining the tocolytic agents atosiban and ritodrine to extend gestation. MATERIAL AND METHODS The study included 52 patients with late threatened abortion and threatened premature labor between 20°â¸7 and 336⸍7 weeks' gestation who were administrated continuous tocolytic agents for 48 h. Patients were divided into a research group receiving ritodrine combined with atosiban, owing to having no response to ritodrine alone (n=30), and a control group receiving ritodrine alone (n=22). The mean infusion rate and duration of tocolytic administration, gestation extension, pregnancy outcomes, and adverse effects were recorded. Routine blood tests, including C-reactive protein, and cultures for leukorrhea, candida, and mycoplasma were performed before and 1 week after treatment. RESULTS Patients receiving ritodrine with atosiban had a mean gestation extension of 42.53±31.70 days. The extension of gestation of the research group was statistically shorter than that of the control group (P<0.05). The fetal loss rate, newborn birth weight, and Apgar score at 1 min were similar between the 2 groups (all, P>0.05). The research group had a lower incidence of palpitations than the control group (P<0.05). CONCLUSIONS For patients with late threatened abortion or threatened premature labor not controlled with ritodrine alone, ritodrine combined with atosiban extends gestation and improves pregnancy outcomes. For patients with abnormal uterine contractions, routine testing for reproductive tract infection should be performed. When infection is present, anti-infective therapy should be administered.

Deleterious genetic variants in ciliopathy genes increase risk of ritodrine-induced cardiac and pulmonary side effects.

BACKGROUND: Ritodrine is a commonly used tocolytic to prevent preterm labour. However, it can cause unexpected serious adverse reactions, such as pulmonary oedema, pulmonary congestion, and tachycardia. It is unknown whether such adverse reactions are associated with pharmacogenomic variants in patients. METHODS: Whole-exome sequencing of 13 subjects with serious ritodrine-induced cardiac and pulmonary side-effects was performed to identify causal genes and variants. The deleterious impact of nonsynonymous substitutions for all genes was computed and compared between cases (n = 13) and controls (n = 30). The significant genes were annotated with Gene Ontology (GO), and the associated disease terms were categorised into four functional classes for functional enrichment tests. To assess the impact of distributed rare variants in cases with side effects, we carried out rare variant association tests with a minor allele frequency ≤ 1% using the burden test, the sequence Kernel association test (SKAT), and optimised SKAT. RESULTS: We identified 28 genes that showed significantly lower gene-wise deleteriousness scores in cases than in controls. Three of the identified genes-CYP1A1, CYP8B1, and SERPINA7-are pharmacokinetic genes. The significantly identified genes were categorized into four functional classes: ion binding, ATP binding, Ca2+-related, and ciliopathies-related. These four classes were significantly enriched with ciliary genes according to SYSCILIA Gold Standard genes (P < 0.01), thus representing ciliary genes. Furthermore, SKAT showed a marginal trend toward significance after Bonferroni correction with Joubert Syndrome ciliopathy genes (P = 0.05). With respect to the pharmacokinetic genes, rs1048943 (CYP1A1) and rs1804495 (SERPINA7) showed a significantly higher frequency in cases than controls, as determined by Fisher's exact test (P < 0.05 and P < 0.01, respectively). CONCLUSIONS: Ritodrine-induced cardiac and pulmonary side effects may be associated with deleterious genetic variants in ciliary and pharmacokinetic genes.

Sulfation of ritodrine by the human cytosolic sulfotransferases (SULTs): Effects of SULT1A3 genetic polymorphism.

Previous studies have demonstrated the metabolism of ritodrine through sulfation. The current study was designed to identify the human SULTs that are capable of sulfating ritodrine and to investigate how genetic polymorphism of the major ritodrine-sulfating SULT, SULT1A3, may affect its sulfating activity. A systematic analysis revealed that of the 13 known human SULTs, SULT1A1, SULT1A3, and SULT1C4, were capable of mediating the sulfation of ritodrine, with SULT1A3 displaying the strongest sulfating activity. Effects of genetic polymorphism on the sulfating activity of SULT1A3 were examined. By employing site-directed mutagenesis, 4 SULT1A3 allozymes were generated, expressed, and purified. Purified SULT1A3 allozymes were shown to exhibit differential sulfating activity toward ritodrine. Kinetic studies further demonstrated differential substrate affinity and catalytic efficiency among the SULT1A3 allozymes. Collectively, these results provided useful information concerning the differential metabolism of ritodrine through sulfation in different individuals.

Ritodrine sulphation in the human liver and duodenal mucosa: interindividual variability.

The beta2-adrenoceptor agonist ritodrine has a bioavailability of 30% due to its presystemic metabolism and sulphation is an important metabolic route. The interindividual variability in the rate of ritodrine sulphation in 100 specimens of human liver and duodenum is reported. The final concentrations of ritodrine were 2 mM (duodenum) and 20 mM (liver). The mean estimates of ritodrine sulphation rate were 490 pmol x min(-1) x mg(-1) (duodenum) and 140 pmol x min(-1) x mg(-1) (liver). There was a 4-5-fold variation within +/- 2 SD units in the hepatic and duodenal rates of ritodrine sulphation. Statistical analysis revealed the presence of at least two subgroups of ritodrine sulphation. In the liver, 30% and 70% of the population fell into two subgroups with the mean estimates of ritodrine sulphation rate of 114 and 149 pmol x min(-1) x mg(-1), respectively (P < 0.05). In the duodenum, 25% and 75% of the population fell into two subgroups and the mean estimates of ritodrine sulphation rate were 332 and 538 pmol x min(-1) x mg(-1), respectively (P < 0.05). The rates of ritodrine and 4-nitrophenol sulphation correlated highly in the liver (r = 0.865; P < 0.001) and the rates of ritodrine and dopamine sulphation correlated highly (r = 0.914; P < 0.001) in the duodenum. In both tissues, the rates of ritodrine and (-)-salbutamol sulphation underwent a similar extent of variation and correlated highly. The intrinsic clearance of ritodrine sulphation was over one order of magnitude higher in the duodenum than in the liver suggesting that the duodenum is an important site of ritodrine sulphation.

Sulphation and glucuronidation of ritodrine in human foetal and adult tissues.

Ritodrine is a beta 2-adrenoceptor agonist used for the management of preterm labour. It is inactivated by conjugation with sulphate and glucuronic acid. There is more ritodrine sulphate than ritodrine glucuronide in urine from the newborn whereas equal amounts of ritodrine glucuronide and sulphate are excreted in maternal urine [Clin. Pharmacol. Ther 44, 634-641, 1988]. We show that, in the mid-gestational human fetal liver, ritodrine sulphotransferase is well expressed, whereas the glucuronidation of ritodrine is little developed compared to the adult liver. The average sulphotransferase activity was 308 pmol.min-1 per mg protein in fetal (N = 48) and 145 pmol.min-1 per mg protein in adult (N = 32) liver. The rates of ritodrine sulphation in fetal gut, lung and kidney were higher than in the corresponding adult tissues. The development and tissue distribution patterns of ritodrine sulphotransferase are consistent with those of dopamine sulphotransferase. Ritodrine and dopamine are sulphated by thermolabile enzymes. The activity of glucuronyl transferase was measurable in only 5 of the 48 foetal livers assayed, and in those in which could be assayed, the average activity was 44.6 pmol.min-1 per mg protein, one-tenth of that in adult livers (524 pmol.min-1 per mg protein).

Ritodrine: a beta-adrenergic receptor antagonist in human amnion.

OBJECTIVE: Human amnion is important in the initiation of labor. Ritodrine, when administered as a tocolytic, is found unchanged in amniotic fluid. We characterized effects of ritodrine binding to beta-adrenergic receptors in amnion and amniocytes. STUDY DESIGN: Iodine 125-iodopindolol, beta-adrenergic receptor agonists, and beta-adrenergic receptor antagonists were used to describe binding characteristics. Experiments were designed with and without isoproterenol and ritodrine to study intracellular cyclic adenosine 3'5'-monophosphate and prostaglandin E2 release. RESULTS: Scatchard analysis revealed a single class of saturable binding sites, with maximum binding capacity of 70.0 +/- 17.2 fmol/mg protein (n = 12) and with high-affinity dissociation constant of 458.9 +/- 72.1 pmol/L. Agonists and antagonists competed for the 125I-iodopindolol binding site consistent with a beta 2-adrenergic receptor. Hill coefficients were 0.6 to 0.8 for agonist competition and 1.0 for antagonist competition and ritodrine. Stimulation with isoproterenol resulted in dose-dependent increases in cyclic adenosine 3'5'-monophosphate and prostaglandin E2. Ritodrine failed to stimulate cyclic adenosine 3'5'-monophosphate and inhibited isoproterenol-stimulated cyclic adenosine 3'5'-monophosphate and prostaglandin E2 production. CONCLUSION: In human amnion binding of ritodrine to beta 2-adrenergic receptors and lack of ritodrine-mediated postreceptor effects are characteristic of a beta 2-adrenergic antagonist.

Transplacental transfer of ritodrine and its effect on placental glucose and oxygen consumption in an in vitro human placental cotyledon perfusion.

Maternofetal transfer of ritodrine and its effect on placental glucose and oxygen consumption were studied using a recycling perfusion of maternal and fetal circulations of an isolated cotyledon of a term human placenta. 3H-labeled ritodrine was introduced into the maternal side of the perfusion system. Transfer was calculated from the linear rise of ritodrine concentrations on the fetal side and was found to be 7.31 +/- 1.02 ng/g placental wet weight/min (SEM) when 1.4 micrograms/ml of ritodrine was used (n = 3) and 14.7 +/- 1.06 ng/g placental wet weight/min when the concentration was 2.8 micrograms/ml (n = 5). The antipyrine transfer rate, 4.1 +/- 0.51 mg/kg/min (n = 8), was used to demonstrate perfusion adequacy and served as an internal standard. Upon computing the mass balance of ritodrine and antipyrine at the end of the experiment, it was found that 17% of ritodrine disappeared from the perfusion system compared to 0.7% of antipyrine (p less than 0.01). The introduction of ritodrine into the perfusion system did not affect placental glucose and oxygen consumption rates of 0.35 +/- 0.01 mumol/g/min (n = 7) and 0.19 +/- 0.013 mumol/g/min (n = 5), respectively.

Structural determination of the conjugated metabolites of ritodrine.

Ritodrine is a beta-2 adrenergic agonist which is used clinically for the management of preterm labor. Since ritodrine is resistant to the action of monoamine oxidase and catecholamine-O-methyltransferase, conjugation is a major route of metabolism. Glucuronide and sulfate conjugates of ritodrine are found in maternal urine. However, the structure of these metabolites has not been determined. The purpose of this study was to determine the structure of these conjugates. Urine from patients on ritodrine therapy was purified by QAE Sephadex ion exchange chromatography. The partially purified conjugates were derivatized and analyzed by GC/MS. The data did not indicate an exclusive site of conjugation. Analysis of both the glucuronide and sulfate conjugates indicates that either of the two phenolic hydroxyl groups may be involved in the formation of conjugated metabolites. However, conjugation of the [2-(p-hydroxyphenyl)-2-hydroxy-1-methylethyl]amine phenolic hydroxyl is more prevalent for both conjugates. This phenolic hydroxyl group is unique since it is located on the portion of the ritodrine molecule which more closely resembles the structure of endogenous catecholamines.

Ritodrine pharmacokinetics.

The purpose of this study was to add to the limited information available regarding the pharmacology of ritodrine in the peripartum period when treatment fails and labor is not inhibited. Plasma or urine samples from eight parturients and 13 infants were studied; in addition plasma samples at delivery were obtained from a total of 26 mothers and infants. All the mothers received ritodrine in the 24 hours before delivery. Plasma and urine ritodrine (free and conjugated) were determined with HPLC by electrochemical detection. In maternal plasma, an apparent rapid distribution phase with a t1/2 of 32 +/- 21 minutes was followed by a prolonged equilibrium phase with a t1/2 of 17 +/- 10 hours. Seventy-six percent of the ritodrine excreted by the mother was in the form of a conjugate. Ninety percent of the ritodrine excreted by the neonate was also excreted in the form of a conjugate.

Interspecies variation in ritodrine metabolism.

The metabolism of ritodrine has been studied in the rat, both in vitro and in vivo, and in the in vivo pregnant baboon, with the use of tritium-labeled drug as a probe. Combined enzymatic degradation and radiochromatography of the radioactive components of bile and urine show that ritodrine undergoes significant Phase l metabolism in addition to conjugation to both sulfate and glucuronide, as previously reported. The presence of more than one conjugate is shown, and evidence for major interspecies variation in patterns of metabolism and conjugation is presented, with comments on the applicability of results to human clinical use.

Metabolism and disposition of ritodrine in a pregnant baboon.

Relatively little is known about the detailed metabolism of ritodrine. The aim of this study was to examine ritodrine metabolism and pharmacokinetics in the maternal and fetal baboon. A fetal-maternal model was made with use of Papio anubis at 144 days of gestation. Tritiated ritodrine was injected as an intravenous bolus into the mother. Maternal and fetal blood samples, amniotic fluid, and maternal urine were collected at time intervals. Samples were analyzed by a combination of high-pressure liquid chromatography and radiochromatography. Conjugated metabolites were recovered and characterized by cleavage studies with use of beta-glucuronidase and sulfatase. The distribution half-life of ritodrine in the mother was 6 minutes and the elimination half-life was 61 minutes. Metabolites were found in both fetal serum and amniotic fluid. The concentrations of ritodrine and its metabolites in fetal serum were at or above the concentrations in maternal serum at 2 hours after maternal intravenous injection. The principal metabolite identified was the sulfate conjugate. The fetus appears to accumulate metabolites. These data indicate that ritodrine crosses the placenta and, in the baboon, achieves levels in the fetus equal to or higher than those in the mother.

Glucuronidation of morphine and six beta 2-sympathomimetics in isolated rat intestinal epithelial cells.

The metabolism of morphine and six beta 2-sympathomimetics (orciprenaline, terbutaline, fenoterol, salbutamol, ritodrine, and bamethan) in isolated rat intestinal epithelial cells was investigated. Only conjugates with glucuronic acid were detected. With regard to observed Vmax values the beta 2-sympathomimetics can be divided in two groups. The three resorcinols (orciprenaline, terbutaline, fenoterol) have a Vmax value comparable to that of morphine (70-230 pmol/min X mg cell protein). The phenolic beta 2-sympathomimetics (salbutamol, ritodrine, bamethan) exhibit a Vmax value comparable to the Vmax value of 1-naphthol (500-1100 pmol/min X mg cell protein). Calculation of intestinal intrinsic (metabolic) clearance and intestinal first pass extraction ratios from Vmax and Kappm values suggests that most of these drugs may undergo substantial intestinal first pass metabolism after oral administration. The glucuronidation of morphine in isolated mucosal cells could be completely inhibited by addition of 1-naphthol (50 microM), salicylamide (5 mM), or fenoterol (5 mM). Glucuronidation of fenoterol could be partially inhibited by 1-naphthol, salicylamide, and morphine. Preliminary data obtained with microsomes suggest that 1-naphthol and morphine are metabolized by different forms of the intestinal microsomal UDP-glucuronosyltransferase. Fenoterol and ritodrine are probably glucuronidated by the form, which also glucuronidates morphine. The results demonstrate that rat intestinal epithelial cells can be used to predict intestinal metabolism of morphine and other drugs at least qualitatively and that phenolic food constituents (e.g. 1-naphthol) and non-prescription drugs (e.g. salicylamide) may affect the intestinal first pass metabolism of morphine and fenoterol.

Plasma protein binding of ritodrine at parturition and in nonpregnant women.

The binding of ritodrine HCl in whole plasma from healthy nonpregnant women, parturients and matched umbilical venous plasma and in solutions of HSA and alpha 1-AGP has been studied by equilibrium dialysis. Binding to plasma from nonpregnant subjects and HSA was independent of ritodrine concentration over a wide range. The free fraction in plasma was high and significantly different between groups of nonpregnant (alpha = 0.64), parturient (alpha = 0.68) and matched umbilical venous plasma (alpha = 0.75). It would seem that variability in transplacental transfer of ritodrine, as a result of plasma binding fluctuations, will be minor.

Transplacental transfer of beta-adrenergic drugs studied by an in vitro perfusion method of an isolated human placental lobule.

A study was made of the transfer across an in vitro perfused human placenta of four beta-mimetics commonly used in obstetric practice. Between 2% and 3% of fenoterol, ritodrine, and salbutamol appeared on the fetal side after bolus injection into the maternal circulation. For hexoprenaline, the transfer (1%) was significantly lower than that observed with other beta-mimetics studied. With constant infusion of fenoterol into the maternal circulation and recycling of a small volume of perfusate on the fetal side, a fairly rapid rise in the concentration was seen. Some sulfate conjugation of fenoterol during its diffusion from the maternal to the fetal side of the placenta could be seen. In the in vitro perfused human placental lobule there is no apparent effect of synthetic beta-mimetics on the transfer of antipyrine or glucose and no stimulation of the production of lactate and pyruvate.

Ritodrine concentrations in maternal and fetal serum and amniotic fluid.

Ritodrine hydrochloride concentrations were measured by radioimmunoassay in maternal and fetal sera and amniotic fluid from eight, pregnant, volunteers. Each patient agreed to have 420 micrograms . kg-1 of ritodrine infused intra-venously over two hours prior to elective cesarian section. During infusion a blood sample was taken every 30 minutes from a maternal peripheral vein. Once anesthesia was established the infusion was discontinued. During surgery, samples were drawn from maternal peripheral vein, uterine vein, umbilical artery and vein, and amniotic fluid. All the children delivered were healthy and had a normal course during the neonatal period. Ritodrine concentrations in maternal and fetal compartments at the time of cesarian section were 54.2 +/- 11.8 ng/ml (mean +/- S.D.) in maternal peripheral vein, 37.5 +/- 10.3 ng/ml in uterine vein, 15.8 +/- 4.8 ng/ml in umbilical artery, 16.6 +/- 8.9 ng/ml in umbilical vein, and 15.2 +/- 8.7 ng/ml in amniotic fluid. There was a statistically significant difference (p less than 0.02, paired-t test) between the mean ritodrine concentrations in sera from the maternal peripheral vein and uterine vein. This difference probably reflects transplacental passage. The mean ratio of fetal vein and peripheral maternal vein serum ritodrine concentrations was 0.30 +/- 0.13 (mean +/- SD). The similarity between mean ritodrine concentrations in amniotic fluid, and sera from umbilical arterial and venous blood was striking. These results suggest that the fetus does not conjugate the drug.

Transfer of ritodrine and norepinephrine in human placenta: in vitro study.

The placental transfer from maternal to fetal circulation of ritodrine, a tocolytic agent used in obstetrics and of a structurally related physiologic catecholamine, norepinephrine was studied in vitro using dual perfusion of isolated human placental lobules. The clearances of ritodrine and norepinephrine represent 34 and 24% respectively of tritiated water clearance taken as reference. The relatively low ritodrine clearance may be explained by its small molecular weight and hydrosoluble nature, but not that of norepinephrine. For the latter, a strong membrane limitation and efficient placental catabolism may be implicated. We conclude that some of the fetal effects of maternal infusion of these amines are the result of the method in which the drug is transferred.

Ritodrine hydrochloride: a betamimetic agent for use in preterm labor. I. pharmacology, clinical history, administration, side effects, and safety.

Ritodrine hydrochloride has become the first drug approved in the United States specifically for use in preterm labor. The drug is a beta-sympathomimetic agent with predominant effects upon beta 2 receptors of the uterus. In this report, the pharmacology, distribution, disposition, and excretion are briefly reviewed. Recommendations for selecting patients most likely to benefit from ritodrine are given, together with the dosage and administration schedules that have been found most effective. Although this drug is not without side effects, it has been more thoroughly evaluated in prospective double-blind controlled trials than any of the other agents commonly used in preterm labor. In comparison with these agents, it seems relatively safe and the side effects are usually well tolerated. Part 2 of the paper discusses the evidence for efficacy.