Rat Uterine Contractions Research Articles

Nocistatin inhibits pregnant rat uterine contractions in vitro: Roles of calcitonin gene-related peptide and calcium-dependent potassium channel

The endogenous neuropeptide nociceptin/orphanin FQ, translated from the prepronociceptin gene, exerts a contraction-inhibitory effect on the rat uterus. As nocistatin has been reported to cause functional antagonism of the pro-nociceptive effects of nociceptin, we set out to investigate its effects on the pregnant rat uterus and to elucidate its signalling pathway. The expression of prepronociceptin mRNA in the uterus and nocistatin levels in the uterus and the plasma were confirmed by RT-PCR and radioimmunoassay. The uterine levels of prepronociceptin mRNA and nocistatin were significantly increased by the last day of pregnancy, while the plasma nocistatin levels remained unchanged. In the isolated organ bath studies nocistatin inhibited the prostaglandin- and the KCl-evoked contractions in the uterus dose-dependently. This latter effect was decreased by preincubation with capsaicin. Incubation with calcitonin gene-related peptide after capsaicin treatment caused an elevation in the contraction-inhibitory effect of nocistatin. The effect of nocistatin was also decreased by the Ca2+-dependent K+ channel inhibitor paxilline, against spontaneous uterine contractions. Nociceptin potentiated the action of nocistatin. Naloxone decreased the effect of nocistatin administered either alone or in combination with nociceptin. In Ca2+-poor environment, this effect of naloxone was suspended. Enzyme immunoassay for the uterine intracellular cAMP levels partially confirmed the results of in vitro contractility studies. We conclude that nocistatin, generated locally in the uterus, exerts an inhibitory effect, the mechanism being mediated in part by Ca2+-dependent K+ channels, the elevation of cAMP levels and sensory neuropeptides.

Effect of leonurine hydrochloride on endothelin and the endothelin receptor-mediated signal pathway in medically-induced incomplete abortion in rats

ObjectiveEndothelin (ET) is involved in uterine contractions. Our previous study showed that leonurine hydrochloride (LH) inhibits abnormal bleeding caused by incomplete abortion through an increase in uterine contractions in rats. The present study was conducted to show that LH treatment regulates the ET-mediated signal pathway in abortion in rats. Study designEarly pregnancies in rats had incomplete abortions induced using mifepristone in combination with misoprostol. After the abortions, the rats were treated with LH orally for 7 days and surgery was performed. The sinistro-uterus was dissected for measurement of ET and nitric oxide (NO); the dextro-uterus was stored at −80°C for ET receptor (ETA and ETB) analysis. Myometrial cells from the dextro-uterus were cultured for measurement of phospholipase C (PLC) activity, intra-cellular Ca2+ concentration ([Ca2+]i), and protein kinase C (PKC) activity. ResultsIn in vivo experiments, LH treatment elevated the ET level and ET/NO ratio in rats with induced abortions and up-regulated ETA mRNA expression (P<0.01 vs. the model group), but there was no change in ETB mRNA. LH significantly increased the [Ca2+]i, PLC activity, and relative production of PKC protein in myometrial cells. ConclusionLH increased uterine contractions in rats with incomplete abortions by modulating the ET receptor-mediated signal pathway.

Differences in direct pharmacologic effects and antioxidative properties of mature breast milk and infant formulas

ObjectiveEarly-onset and exclusive breast-feeding provides a significant health benefit to infants compared with infant formulas. The aim of this study was to compare mature breast milk with standard infant formulas by examining their effects on non-vascular smooth muscle contraction and their antioxidative properties. MethodsThe pharmacologic effects of breast milk and formulas were examined using a model system of the rat uterine smooth muscle contraction. Electron paramagnetic resonance spin-trapping spectroscopy was used to compare the antioxidative capacities of breast milk (obtained in the ninth week of lactation) with commercial infant formulas against hydroxyl radical production in the Fenton reaction. The activities of superoxide dismutase, glutathione peroxidase, and the sulfhydryl group were determined in the breast milk and infant formulas. ResultsIn contrast to the infant formulas, breast milk exerted a relaxing effect on isolated non-vascular smooth muscle. In general, breast milk showed higher antioxidative activity compared with the infant formulas. In all samples, the generation of hydroxyl radicals led to the formation of carbon-centered and ascorbyl radicals. ConclusionsHuman milk exerts direct pharmacologic relaxation effects and provides better antioxidant protection compared with infant formulas because of the presence of specific enzymatic components, such as human superoxide dismutase. We propose that these effects should be advantageous to an infant's gastrointestinal tract by supporting the normal work of the smooth musculature and maintaining redox homeostasis and may represent one of the mechanisms by which breast-feeding benefits health.

Inhibitory action on rat uterine muscle contraction in vitro and acute toxicity in rats of the Thai traditional preparation Prasaplai

The activity of an aqueous extract of Prasaplai, a Thai traditional medicine, was studied on the isolated rat uterus in the oestrus stage. The results showed that the extract inhibited the contraction induced by a submaximal dose of acetylcholine (2.04 × 10−4 mg mL−1), oxytocin (1.54 × 10−4mg mL−1) and prostaglandin E2 (PGE2) (6.00 × 10−4 mg mL−1). The inhibition was concentration-dependent and reversible by tissue washing. The IC50 of Prasaplai extracts expressed as milligram of powdered preparation per millilitre of perfusion solution for acetylcholine, oxytocin and PGE2 were 11.70, 10.00 and 5.75 mg mL−1, respectively. These data reveal that Prasaplai has an antispasmodic effect against uterine contraction by different mechanisms and corroborate the traditional use in the treatment of dysmenorrhoea. Oral administration of single dose of the water extract, calculated as powdered Prasaplai up to 20 g kg−1 in rats, showed no sign and symptom of acute toxicity, and no rat died even at the maximum dose.

Effects of Oxytocin Antagonist (dTVT) and Ritodrine on Spontaneous and Oxytocics-Induced Uterine Contractions in Pregnant Rats

The effect of a recently developed oxytocin antagonist dTVT, i.e. deamino-[2-D-tyrosine(OEt)-4-threonine-8-ornithine] oxytocin on uterine contraction of pregnant rats was studied in vitro. The following results were obtained. 1. dTVT treatment did not affect spontaneous PGE2- or PGF2 alpha-stimulated contraction, while it slightly suppressed PGE1 analogue (Gemeprost)-stimulated contraction of the uterus. 2. Following treatment with dTVT (5-50 micrograms/ml), oxytocin-stimulated uterine contraction was gradually and slowly suppressed, resulting in an attenuation curve. Ritodrine treatment, on the other hand, rapidly suppressed spontaneous uterine contraction as well as contraction stimulated by various oxytocics. Suppression of oxytocin-stimulated uterine contraction by dTVT took much longer (14.8 +/- 1.1 min) to take effect than that by ritodrine (less than 1 min).

Structural requirement of spirostanol glycosides for rat uterine contractility and mode of their synergism

Total steroidal saponins extracted from the rhizome of Paris polyphylla (TSSP) have been used in China for the treatment of abnormal uterine bleeding. The aim of this study was to analyse the structure-activity relationship of steroidal saponins purified from P. polyphylla Sm. var. yunnanensis on rat myometrial contractions, and investigate the synergism among themselves as well as with known inherent agonists, such as Prostaglandin F(2alpha) (PGF-2alpha). In this study, 22 steroidal saponins purified from TSSP were screened for their contractile activity in isolated uterine strips from estrogen-primed rats. It was shown that spirostanol glycosides exhibited inducible or inhibitory activity in rat uterine contraction based on the difference of their structures, which was not only attributed in part to the number, the length and the position of sugar side chains attached by a glycoside, but also related to the structure of the aglycone. Furthermore, synergistic actions were observed among pennogenin or diosgenin glycosides as well as with the known inherent agonist PGF-2alpha, indicating they may share, at least in part, similar pathways with PGF-2alpha in stimulating myometrial contractions. Finally, the contractile response of rat myometrium to spirostanol glycosides was significantly enhanced with advancing pregnancy. Together, these data support the possibility that some spirostanol glycosides may represent a new type of contractile agonist for the uterus and their synergism may be responsible for the therapeutic effect of TSSP on abnormal uterine bleeding.

A Functional Role for Nicotinic Acid Adenine Dinucleotide Phosphate in Oxytocin-Mediated Contraction of Uterine Smooth Muscle from Rat

Conventionally, G protein-coupled receptors are thought to increase calcium via inositol 1,4,5-trisphosphate (InsP(3)). More recent evidence shows that an alternative second messenger, nicotinic acid adenine dinucleotide phosphate (NAADP), also has a role to play, causing researchers to question established calcium releasing pathways. With the recent development, by our group, of cell-permeant NAADP (NAADP-aceteoxymethyl ester) and a selective NAADP receptor antagonist (Ned-19; 1-(3-((4-(2-fluorophenyl)piperazin-1-yl)methyl)-4-methoxyphenyl)-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole-3-carboxylic acid),the ability to investigate this signaling pathway has improved. Therefore, we investigated a role for NAADP in oxytocin-mediated responses in the rat uterus. Oxytocin- and NAADP-mediated effects were investigated by using contractile measurements of whole uterine strips from rat in organ baths. Responses were correlated to calcium release in cultured rat uterine smooth muscle cells measured by fluorescence microscopy. Inhibition of both oxytocin-induced contraction and calcium release by the traditional NAADP-signaling disrupter bafilomycin and the NAADP receptor antagonist Ned-19 clearly demonstrated a role for NAADP in oxytocin-induced signaling. A cell-permeant form of NAADP was able to produce both uterine contractions and calcium release. This response was unaffected by depletion of sarcoplasmic reticulum stores with thapsigargin, but was abolished by both bafilomycin and Ned-19. Crucially, oxytocin stimulated an increase in NAADP in rat uterine tissue. The present study demonstrates directly that NAADP signaling plays a role in rat uterine contractions. Moreover, investigation of this signaling pathway highlights yet another component of oxytocin-mediated signaling, stressing the need to consider the action of new components as they are discovered, even in signaling pathways that are thought to be well established.

The Effects of Pomegranate Seed Extract and β-Sitosterol on Rat Uterine Contractions

The aim of this study was to investigate the effects of pomegranate (Punica granatum L., Punicaceae) seed extract on uterine contractility. Pomegranate seeds were methanolic extracted and their constituents analyzed using gas chromatography and mass spectrometry. Isometric force was measured in strips of longitudinal rat myometrium and the effects of pomegranate seed extract studied. We found beta-sitosterol to be the main constituent of the extract (16%) and its effects were also investigated. Pomegranate seed extract and beta-sitosterol increased spontaneous contractions in a concentration-dependent manner with a maximum effect at 250 mg/100 mL and 1 mg/100 mL, respectively. The amplitude and frequency of the phasic contraction were significantly increased along with basal tension. The effects of pomegranate seed extract were very similar to those of beta-sitosterol. Force produced in the presence of pomegranate seed extract was abolished by the inhibition of L-type calcium channels or myosin light chain kinase (MLCK). Contractions were not potentiated by pomegranate extract following the inhibition of K channels or inhibition of the sarcoplasmic reticulum calcium ATPase (SERCA). The actions of beta-sitosterol and the extract were not blocked by the estrogen receptor blocker, fulvestrant. We conclude that pomegranate seed extract is a potent stimulator of phasic activity in rat uterus. Our data suggest that the uterotonic effect is due to nonestrogenic effects of beta-sitosterol acting to inhibit K channels and SERCA and thereby increasing contraction via calcium entry on L-type calcium channels and MLCK. We suggest that pomegranate extract and beta-sitosterol may be a useful uterine stimulant.

Modification of the effect of nifedipine in the pregnant rat myometrium: The influence of progesterone and terbutaline

Aims The aims of the study were to investigate the effects of nifedipine on potassium chloride (KCl)-evoked rat uterine contractions on different days of pregnancy in vitro, and the alterations in the effects of nifedipine on combination with terbutaline or progesterone. Main methods In rat myometrial rings taken on different days of pregnancy, rhythmic contractions were evoked with KCl in an isolated organ bath. Key findings The relaxing effect of nifedipine was most expressed in the 25 mM KCl-induced uterine contractions, reaching the maximum on the last day of pregnancy (day 22). This effect was decreased by progesterone pretreatment in vivo. Synergism was observed in the uterus-relaxing effect of nifedipine +terbutaline, though the extent of potentiation depended on the sequence of administration of the two compounds. When terbutaline was added first in a single dose, the maximal inhibitory effect of nifedipine was lower. This decrease in the inhibition was suspended by a Ca 2+-poor buffer, indicating the role of Ca 2+ channel activating effect of terbutaline. Significance It is concluded that the uterus-relaxing effect of nifedipine is weakened by progesterone and may be enhanced by low concentrations of β-mimetics. However, the administration of terbutaline cannot precede the administration of nifedipine.

Stimulatory effects of a microbially dechlorinated polychlorinated biphenyl (PCB) mixture on rat uterine contraction in vitro

Microbially mediated reductive dechlorination has been advocated as the first part of a two-stage (anaerobic/aerobic) biotreatment process for polychlorinated biphenyls (PCBs) in sediments, and is generally viewed as a detoxication process. However, previous studies suggest that microbial dechlorination increases the ability to stimulate uterine contractions compared with the original PCB mixtures. Here, we investigate the composition and uterotonic activity of the commercial PCB mixture Aroclor 1260 before and after incubation with microorganisms eluted from PCB-contaminated sediment of the Hudson River. Incubation with microorganisms resulted in a partially dechlorinated mixture (HR1260) dominated by ortho-substituted PCBs with four or fewer chlorines per biphenyl. Aroclor 1260 that had not been incubated with microorganisms had no significant effect on contraction frequency of rat uterine strips (gestation day 10) in vitro, whereas HR1260 dramatically increased contraction frequency to 718±134% of the basal rate at a total PCB concentration of 70 μM ( p<0.05). The microbial dechlorination increased 2,2′,4,4′-tetrachlorobiphenyl and one or more of four congeners that co-eluted during chromatography (2,3,3′,5-tetrachlorobiphenyl, 2,3′,4,5-tetrachlorobiphenyl, 2,2′,4,4′,6-pentachlorobiphenyl and 2,2′,4,5′,6-pentachlorobiphenyl) to 24 and 8 mol%, respectively. However, the uterotonic activities of the latter congeners were modest when evaluated either solely or in a reconstituted mixture and could not fully account for the uterotonic activity of HR1260. Nonetheless, the relative abundance of congeners with three or fewer chlorines increased to 14 mol% as a group in HR1260, suggesting that these congeners collectively contribute to the uterotonic activity even though the abundance of any one congener in this group was less than 5 mol%.

Arrest of preterm labor in rat and mouse by an oral and selective nonprostanoid antagonist of the prostaglandin F2α receptor (FP)

The purpose of this study was to assess the tocolytic effect of AS604872, an orally active, potent, and selective prostanoid prostaglandin F2alpha receptor (FP) antagonist. Compound AS604872 was characterized and tested for its ability to block uterine contraction and delay preterm parturition in rodent models. AS604872 inhibited spontaneous uterine contractions in pregnant rat near term. In pregnant mouse, AS604872 delayed parturition induced by either the antiprogesterone RU-486 or the endotoxin lipopolysaccharide. Pups from treated mothers were delivered alive. The efficacy of AS604872 was superior to the beta-mimetic drug ritodrine. Combination of AS604872 and ritodrine showed an additive inhibitory effect on spontaneous uterine contractions in rat. A selective antagonist of the FP receptor suppresses uterine contractility and delays labor. Our findings identify a new potential modality for the pharmacological management of preterm labor.

Tocolytic effect of a selective FP receptor antagonist in rodent models reveals an innovative approach to the treatment of preterm labor

BackgroundManagement of preterm labor by tocolysis remains an unmet medical need. Prostaglandins play a major role in regulation of uterine activity and in molecular mechanisms of human labor and parturition. There is some circumstantial evidence that prostaglandin F2α by action through the prostaglandin receptor subtype FP is effective in key events during labor uterine contraction, rupture of membranes and cervical dilation. This role of FP is briefly reviewed. In this study, we tested the hypothesis that an orally active and selective FP antagonist may arrest labor and delay parturition in animal models.MethodsWe examined the effects of a small molecule selective antagonist of the FP receptor (AS604872) in inhibition of spontaneous uterine contraction in pregnant rat near term. We tested AS604872 for its ability to delay preterm birth in a mouse model in which the anti-progestin agent RU486 triggered parturition.ResultsBy oral or intravenous dosing AS604872 reduced markedly and dose-dependently the spontaneous uterine contractions in late-term pregnant rats at gestational days 19–21. In pregnant mice, AS604872 delayed the preterm birth caused by RU486 administration. The effect was dose-dependent with a significant increase in the mean delivery time of 16 and 33 hours at oral doses of 30 mg/kg and 100 mg/kg, respectively, in the case of labor triggered at gestational day 14. In both models AS604872 appeared more effective than the β-agonist ritodrine.ConclusionThe tocolytic activity displayed by a selective FP receptor antagonist supports a key role for the FP receptor in the pathophysiology of premature birth and demonstrates the therapeutic potential of an FP antagonist for the treatment of preterm labor cases in which uterine hyperactivity plays a dominant role.

Use of a novel and highly selective oxytocin receptor antagonist to characterize uterine contractions in the rat

Spontaneous and induced uterine contractions in the rat were found to be inhibited by a novel and selective oxytocin receptor antagonist GSK221149A (3R,6R)-3-Indan-2-yl-1-[(1R)-1-(2-methyl-1,3-oxazol-4-yl)-2-morpholin-4-yl-2-oxoethyl]-6-[(1S)-1-methylpropyl]-2,5-piperazinedione. GSK221149A displayed nanomolar affinity (K(i) = 0.65 nM) for human recombinant oxytocin receptors with >1,400-fold selectivity over human V1a, V1b, and V2 receptors. GSK221149A had similar affinity (K(i) = 4.1 nM) and selectivity for native oxytocin receptors from rat and produced a functional, competitive block of oxytocin-induced contractions in isolated rat myometrial strips with a pA(2) value of 8.18. Intravenous administration of GSK221149A produced a dose-dependent decrease in oxytocin-induced uterine contractions in anesthetized rats with an ID(50) = 0.27 +/- 0.60 mg/kg (corresponding plasma concentrations were 88 ng/ml). Oral administration of GSK221149A (5 mg/kg) was effective in inhibiting oxytocin-induced uterine contractions after single and multiple (4-day) dosing. Spontaneous uterine contractions in late-term pregnant rats (19-21 days gestation) were significantly reduced by intravenous administration of 0.3 mg/kg of GSK221149A. These results provide further evidence that selective oxytocin receptor antagonism may offer an effective treatment for preterm labor.

Effects of pomegranate extracts on rat uterine contraction

Effects of pomegranate extracts on rat uterine contraction

The Effects of Ginger Oils on Rat Uterine Contraction

Ginger, the rhizome of Zingiber officinale Roscoe (Zingiberaceae), has been extensively studied for its pharmacological activities [1]. It produced inhibitory effects on vascular and gut contractility [2, 3]. However, its effects on uterine contractility have not been elucidated. The aims of the study were to investigate the effects of ginger on rat uterine contraction. We examined the effects of ginger oils on phasic contractions arising either spontaneously or PGF2α stimulation and the mode of action. Ginger oils were obtained by water distillation. Rats were killed by asphyxiation with CO2 and longitudinal uterine smooth muscles isolated. Isometric force was measured and the effects of ginger oils studied. The results showed that at each concentration (10–100 microL/100mL) ginger oils reduced spontaneous contractions, and that the effect was dose dependent. The PGF2α-induced contractions were significantly reduced by ginger oils. Increases in external calcium concentration completely reversed the relaxant effects of ginger oils. In conclusion, ginger oils are potent inhibitors of phasic activity in rat uterus, irrespective of how it is produced, and our data suggest their effects lie at the surface membrane.

Discovery and Development of a New Class of Potent, Selective, Orally Active Oxytocin Receptor Antagonists

We report a novel chemical class of potent oxytocin receptor antagonists showing a high degree of selectivity against the closely related vasopressin receptors (V1a, V1b, V2). An initial compound, 7, was shown to be active in an animal model of preterm labor when administered by the intravenous but not by the oral route. Stepwise SAR investigations around the different structural elements revealed one position, the arenesulfonyl moiety, to be amenable to structural changes. Consequently, this position was used to introduce a variety of substituents to improve the physicochemical properties. Some of the resulting analogues were found to be superior to 7 both in terms of potency in vitro and aqueous solubility, which translated into significantly improved efficacy in the animal model after intravenous and oral administration. The best compound, 73, potently inhibited oxytocin-induced uterine contractions in nonpregnant rats and reduced spontaneous uterine contractions in late-term pregnant rats.

Mechanisms of lipopolysaccharide-induced changes in effects of contractile agonists on pregnant rat myometrium

ObjectiveThe study was undertaken to investigate the mechanisms underlying enhanced uterine contractility induced by lipopolysaccharide (LPS) in pregnant rats. Study designWistar rats were administered intrauterine either LPS (50 μg) or normal saline solution (0.05 mL) on day 17 of gestation. On day 19, the animals were killed and uterus was isolated for isometric recording, 45Ca++ influx measurement, and determination of plasma membrane Na+-K+-ATPase. ResultsUterine strips, taken from LPS-treated rats, displayed a marked increase in amplitude of spontaneous rhythmic contractions compared with controls. Enhancement in the sensitivity of uterine strips to agonists such as oxytocin, 5-hydroxytryptamine (5-HT), and BAY K8644 was also observed in rats treated with LPS. Cyclo-oxygenase-2 inhibitor, nimesulide (10 μmol/L) had no significant effect on the LPS-induced increase in spontaneous rhythmic contractions. On the other hand, nimesulide attenuated the increased sensitivity of uterine strips to oxytocin induced by LPS. Nimesulide significantly inhibited 5-HT–induced uterine contractions in both control and LPS-treated rats. However, the enhanced sensitivity of uterine strips to 5-HT was evident even in the presence of nimesulide in rats treated with LPS. Nifedipine-sensitive 45Ca++-influx into uterine strips both in the basal state as well as those stimulated by high K+ (80 mmol/L) and 5-HT (1 μmol/L) was greater in LPS-treated group compared with the controls. LPS treatment caused a marked inhibition in the Na+-K+-ATPase activity of the uterine plasma membrane compared with controls. LPS had no effect on plasma 17β-estradiol levels. ConclusionLPS appears to increase uterine contractility of pregnant rats both through the release of endogenous prostaglandins and increased influx of Ca++ through L-type Ca++ channels. Inhibition of sodium pump by LPS may be an additional mechanism in augmentation of uterine excitability.

Effect of benzyl isothiocyanate on spontaneous and induced force of rat uterine contraction

The present study examines the effect of benzyl isothiocyanate (BITC) on uterine contraction in vitro. BITC (10–320 μM) caused irreversible, concentration-dependent inhibition of the spontaneous, prostaglandin F 2α (PGF 2α) and oxytocin-induced force of gravid and non-gravid rat uterine contractions in contrast to equivalent concentrations of DMSO (solvent control). At 160 μM of BITC, spontaneous, PGF 2α and oxytocin-induced force of gravid rat myometrial contractions were reduced to 16±6%, 15±7% and 17±4% (of the control contractions), respectively. Moreover, at 320 μM of BITC, spontaneous, PGF 2α and oxytocin-induced force of non-gravid rat uterine contractions were reduced to 10±5%, 4±1% and 7±2% (of the control contractions), respectively. Incubation of isolated non-gravid rat uterine strips in Ringer Locke solution containing 100 μM of BITC for 1 h prior to recording their activity also caused significant and irreversible depression of KCl (60 mM)-induced tension development in the uterus relative to the solvent control ( P<0.01). In 56% of BITC-pretreated uterine tissues, spontaneous contractions were totally abolished. Cryosections of BITC-treated uterus (hematoxyline and eosin stained) examined under light microscope revealed structural disintegrity with marked vacuolar degeneration of the endometrium and myometrium. It thus appears that like the vascular smooth muscle (reported by previous workers), BITC is also capable of causing functional aberration of isolated uterus by provoking degeneration of the myometrium.

Effect of 14-deoxyandrographolide on calcium-mediated rat uterine smooth muscle contractility.

In this study, the effect of 14-deoxyandrographolide (14-DAP) on calcium channel-dependent rat uterine smooth muscle contraction was evaluated. Using a tissue bath preparation, 14-DAP was able to reduce the contractile response to 0.3 and 3.0 mm of CaCl(2), with an IC(50) of 1.24 +/- 0.23 x 10(-5) m and 5.94 +/- 0.29 x 10(-5) m, respectively. 14-DAP shifted the CaCl(2) cumulative dose response curve to the right, increasing the EC(50) from 2.08 +/- 0.20 x 10(-4) m to 4.22 +/- 0.22 x 10(-4) m (5 micrometer 14-DAP) and 2.5 +/- 1.0 x 10(-3) m (50 micrometer 14-DAP). In order to determine if 14-DAP had any effect on intracellular calcium, the relaxant response to 14-DAP following contraction by oxytocin, PGF(2alpha) and vanadate in Ca(+2)-free solution was compared with that of isoproterenol and phenylbutazone. While isoproterenol and phenylbutazone relaxed the smooth muscle in a dose-dependent manner, 14-DAP did not have any effect on either the oxytocin, PGF(2alpha) or vanadate-induced smooth muscle contraction. Based on these data, it appears that 14-DAP is an uterine smooth muscle relaxant which produces a selective blockade of voltage operated calcium channels.

Synergistic effects of DL111-IT in combination with mifepristone and misoprostol on termination of early pregnancy in preclinical studies

This study evaluated the effectiveness and acute toxicity of DL111-IT combined with mifepristone (RU486) and misoprostol (MISO) on early pregnancy termination. In the pregnant rats experiments, the ED 50 values of RU486 in two-drug combinations were 0.16 (combined with DL111-IT) and 0.40 (combined with MISO) mg · kg −1 · d −1, while in three-drug combination treatment group (DL111-IT 9.0 mg · kg −1 (<ED 5) + MISO 0.30 mg · kg −1 + RU486 0.012–0.5 mg · kg −1 · d −1), the ED 50 of RU486 was decreased to 0.07 (0.04–0.10) mg · kg −1 · d −1. In guinea pigs, significant enhancement of early pregnancy termination was only observed in three-drug combination treatment with MISO 0.10 mg · kg −1 + RU486 0.05 mg · kg −1 (<minimum effective doses) + high dosages of DL111-IT (0.05–0.10 mg · kg −1). DL111-IT induced pregnant rat uterine contraction in vitro, and the contractive efficacy was 60% of that induced by MISO. Multiple intramuscular injections of DL111-IT in vivo could significantly enhance the MISO-stimulated uterine contractions of pregnant rats in vitro. DL111-IT 600 mg · kg −1 or RU486 1000 mg · kg −1 induced pigeon vomiting, with latent periods of 32.3 ± 12.0 min and 50.4 ± 16.0 min, respectively. In three-drug combination group, the latent period of vomiting was significantly extended to 86.3 ± 36.2 min. MISO also significantly decreased the frequency of vomiting within 4 h after administration of DL111-IT and RU486. In the experiment of mice acute toxicity, the LD 50 values and 95% confidence limit of DL111-IT (i.p.) alone and in combination with RU486 and MISO were 1379.4 (1278.2–1514.7) mg · kg −1 and 1574.1 (1407.8–1762.7) mg · kg −1, respectively. There was no significant difference. All data suggested that DL111-IT in combination with RU486 and MISO significantly increased the effect on early pregnancy termination without increasing acute toxicity compared to the treatment of DL111-IT alone, and this combination may be a promising regimen for early pregnancy termination.