Shakuyaku-kanzo-to inhibits smooth muscle contractions of human pregnant uterine tissue in vitro.

AIM: Shakuyaku-kanzo-to (SK) is a herbal medicine and is known to possess an antispasmodic effect on skeletal muscle and intestinal smooth muscle. However, it is unclear whether SK is effective in antagonizing uterine smooth muscle contractions. Herein, we investigated the effects of SK on smooth muscle contractions of human pregnant uterine samples. MATERIAL AND METHODS: We prepared myometrial strips from uterine tissues of pregnant women who underwent cesarean section for obstetrical indications, and examined the inhibitory effects of SK and its components, shakuyaku (S) and kanzo (K), on agonist-induced and spontaneous contractions in vitro. Oxytocin, prostaglandinF(2α) , and high KCl were utilized as agonists in this study. RESULTS: SK inhibited agonist-induced and spontaneous contractions in a dose-dependent manner. Inhibition of SK on oxytocin-induced contractions occurred at a concentration of 100 µg/mL and reached maximum effect at a concentration of more than 1000 µg/mL. The half max inhibitory concentration of SK was approximately 440 µg/mL in oxytocin-induced contractions. SK at 1000 µg/mL completely inhibited the oxytocin- and prostaglandinF(2α)-induced contractions but not the high KCl-induced contractions. The inhibitory effects on agonist-induced contractions of K, but not S, matched those of SK. CONCLUSION: These results suggest that the inhibitory effect of SK on smooth muscle contractions is due to K. The mechanism of the inhibitory effects of SK on oxytocin- and prostaglandinF(2α) -induced contractions may differ from that on KCl-induced contractions.

Relaxant effect induced by wogonin from Scutellaria baicalensis on rat isolated uterine smooth muscle.

CONTEXT: Wogonin is a flavone derivative isolated from Scutellaria baicalensis Georgi (Labiatae) root, which is a traditional Chinese drug used as an anti-inflammatory and for management of dysmenorrhea. OBJECTIVE: The effect of wogonin on the uterus has not yet been examined. We investigated the relaxant effects of wogonin on contractile activity of isolated uterine strips of rats. MATERIALS AND METHODS: The effect of wogonin on spontaneous uterine contraction, and uterine contraction induced by agonists, K⁺-depolarization and oxytocin in Ca²âº-free solution was observed. To clarify the type of potassium channel, we tested the effects of 4-aminopyridine, tetraethylammonium and glibenclamide. RESULTS: Wogonin reduced the contractile amplitude of uterine strip smooth muscle of rats in a dose-dependent manner. The concentration of wogonin for reducing the contraction amplitude by 50% (IC50) on spontaneous contractions was 60.5 µM. Wogonin also inhibited the contraction induced by three agonists (oxytocin, prostaglandin F(2α) and acetylcholine). For the uterine strips pretreated with oxytocin in Ca²âº-free solution or K⁺-depolarization, wogonin showed relaxant effect on the induced uterine contractions. In addition, whereas the inhibitive effect of wogonin on the contraction of uterine smooth muscle in rats could be partly blocked by 4-aminopyridine and tetraethylammonium, it was not influenced by glibenclamide. DISCUSSION AND CONCLUSION: Wogonin significantly inhibited the contraction of rat uterine smooth muscle probably through the inhibition of the inflow of extracellular calcium into cells via cell membrane, and intracellular release of calcium ions. In addition, the relaxant effect induced by wogonin might be due in part to the opening of voltage-dependent and large conductance Ca²âº-activated K⁺ channels.

Pharmacokinetic-pharmacodynamic modeling of the inhibitory effects of naproxen on the time-courses of inflammatory pain, fever, and the ex vivo synthesis of TXB2 and PGE2 in rats.

PURPOSE: To quantify and compare the time-course and potency of the analgesic and antipyretic effects of naproxen in conjunction with the inhibition of PGE(2) and TXB(2). METHODS: Analgesia was investigated in a rat model with carrageenan-induced arthritis using a gait analysis method. Antipyretics were studied in a yeast-induced fever model using telemetrically recorded body temperature. Inhibition of TXB(2) and PGE(2) synthesis was determined ex vivo. Pharmacokinetic profiles were obtained in satellite animals. Population PKPD modeling was used to analyze the data. RESULTS: The IC(50) values (95% CI) of naproxen for analgesia (27 (0-130) µM), antipyretics (40 (30-65) µM) and inhibition of PGE(2) (13 (6-45) µM) were in similar range, whereas inhibition of TXB(2) (5 (4-8) µM) was observed at lower concentrations. Variability in the behavioral measurement of analgesia was larger than for the other endpoints. The inhibition of fever by naproxen was followed by an increased rebound body temperature. CONCLUSION: Due to better sensitivity and similar drug-induced inhibition, the biomarker PGE(2) and the antipyretic effect would be suitable alternative endpoints to the analgesic effects for characterization and comparisons of potency and time-courses of drug candidates affecting the COX-2 pathway and to support human dose projections.

Hypothalamic oxytocin mediates adaptation mechanism against chronic stress in rats.

Accumulation of continuous life stress (chronic stress) often causes gastric symptoms. Although central oxytocin has antistress effects, the role of central oxytocin in stress-induced gastric dysmotility remains unknown. Solid gastric emptying was measured in rats receiving acute restraint stress, 5 consecutive days of repeated restraint stress (chronic homotypic stress), and 7 consecutive days of varying types of stress (chronic heterotypic stress). Oxytocin and oxytocin receptor antagonist were administered intracerebroventricularly (icv). Expression of corticotropin-releasing factor (CRF) mRNA and oxytocin mRNA in the paraventricular nucleus (PVN) of the hypothalamus was evaluated by real-time RT-PCR. The changes of oxytocinergic neurons in the PVN were evaluated by immunohistochemistry. Acute stress delayed gastric emptying, and the delayed gastric emptying was completely restored after 5 consecutive days of chronic homotypic stress. In contrast, delayed gastric emptying persisted following chronic heterotypic stress. The restored gastric emptying following chronic homotypic stress was antagonized by icv injection of an oxytocin antagonist. Icv injection of oxytocin restored delayed gastric emptying induced by chronic heterotypic stress. CRF mRNA expression, which was significantly increased in response to acute stress and chronic heterotypic stress, returned to the basal levels following chronic homotypic stress. In contrast, oxytocin mRNA expression was significantly increased following chronic homotypic stress. The number of oxytocin-immunoreactive cells was increased following chronic homotypic stress at the magnocellular part of the PVN. Icv injection of oxytocin reduced CRF mRNA expression induced by acute stress and chronic heterotypic stress. It is suggested that the adaptation mechanism to chronic stress may involve the upregulation of oxytocin expression in the hypothalamus, which in turn attenuates CRF expression.

Oxytocin both increases proliferative response of peripheral blood lymphomonocytes to phytohemagglutinin and reverses immunosuppressive estrogen activity.

BACKGROUND: It has been shown that the neurohypophyseal peptide oxytocin is present in the human thymus and in vitro it can mimic interleukin (IL)-2 action in the induction of interferon-gamma production. In the present study, we tested the capacity of oxytocin to modulate the response of peripheral blood mononuclear cells (PBMCs) to phytohemagglutinin (PHA) and its ability to change the membrane expression of IL-2 receptor CD25 and the CD95 activation marker. Furthermore, whether oxytocin was able to reverse the inhibition of PBMC blastic response and CD25 expression induced by estradiol benzoate (E(2)B) was studied. PATIENTS AND METHODS: Fifteen healthy women were studied with a mean age of 33.8 years, no previous pregnancies, all in the early follicular phase of the cycle with normal values of circulating estrogens. RESULTS: The addition of oxytocin (1x10(-10) M, 1x10(-11) M, 1x10(-12) M) significantly increased the PBMC blastic response to PHA as well as the expression of both CD25 and CD95. These results were due to interaction of oxytocin with its specific receptor since the addition of an oxytocin antagonist completely reversed the oxytocin activity. In contrast, E(2)B induced a marked decrease of PHA-stimulated PBMC cell cycle progression and CD25 expression: the inhibitory effect of E(2)B was significantly counteracted by low concentrations of oxytocin. CONCLUSION: The present results support the hypothesis that neuropeptides may act as a link in the network between the immune and the neuroendocrine systems.

Atosiban and nifedipin for the treatment of preterm labor.

OBJECTIVE: To perform a comparison between atosiban (oxytocin antagonist) and nifedipin (calcium channel blocker) for acute treatment of preterm labor and their maternal safety. METHODS: A randomized controlled trial study was performed on 80 pregnant women with preterm labor, between 26 and 34 weeks of pregnancy, in Akbar Abadi Teaching Hospital in Tehran, Iran. 40 women (the atosiban group) were compared with another 40 women (the nifedipin group) for the drugs' efficacy in delaying delivery for more than 48 h in order to undergo steroid therapy, and for more than 7 days or more, and also to assess their maternal safety. The duration between the drugs' administration and delivery were compared. The statistical analysis was performed using the Statistical Package for Social Science (SPSS). RESULTS: There was no statistically significant difference between the two groups in the treatment of preterm labor. Atosiban was effective in 82.5% of cases, and nifedipin in 75% of the cases (p=1.000), for delaying delivery for 48 h. Atosiban was effective in 75% of the cases, and nifedipin in 65% of the cases, for delaying delivery for more than 7 days. The maternal side effects in the atosiban group were 17.5%, and in the nifedipin group they were 40%, which had a statistically significant difference (p=0.027). The duration between treatment and delivery was 29.03+/-16.12 days in the atosiban group and 22.85+/-13.9 days in the nifedipin group with no statistically significant difference (p=0.79). CONCLUSION: Atosiban is an effective and safe drug for the acute treatment of preterm labor with minimal side effects, and it can be an option in the treatment of preterm labor, especially in patients with heart disease and multi-fetal pregnancies.

The pharmacology of a new oxytocic principle from ox hypothalamus.

1. An oxytocic substance has been isolated from ox hypothalamus by successive gel filtration on Sephadex G-25 and Sephadex G-50, and its pharmacology has been examined on three smooth muscle preparations.2. The substance has the same order of potency on rat uterus, guinea-pig ileum, and hen rectal caecum.3. The action of the substance on rat uterus was not abolished by thioglycollate.4. Atropine (1.0 mug/ml.), phenoxybenzamine (0.1 mug/ml.) and mepyramine (1.0 mug/ml.) did not block the smooth muscle action of the substance.5. Drug action, relative potency, and log dose-response relationships distinguish the substance from 5-hydroxytryptamine, acetylcholine, oxytocin, vasopressin, angiotensin amide, bradykinin, and purified preparations of substance P.

Effect of polyphloretin phosphate on the response of non-gravid rat uterus to folkloric and standard oxytocics in vitro.

Polyphloretin phosphate (PPP) has been reported by previous workers to be a specific antagonist of prostaglandin (PGE(1), PGE(2) & PGF(2 alpha))-induced contractions of isolated jird colon, gerbil colon, guinea pig ileum, and rabbit jejunum. In the present study, we examined the effect of PPP on uterotonic activities of crude papaya latex (a folkloric oxytocic), PGF(2 alpha), oxytocin, acetylcholine, and 5-hydroxytryptamine (standard oxytocics) on non-gravid, oestrogen-primed (50 microg/kg) rats in vitro. The effect of PPP on the oxytocics was evaluated qualitatively by incubating the tissues in PPP (25 - 400 microg/ml) for 20 min prior to the addition of a constant concentration of each oxytocic. PPP concentration dependently inhibited the contractile response of the uterine muscles to all the oxytocics. The inhibition was reversible after washing out the drugs. Results of the present study suggest that PPP is a non-specific and reversible antagonist of the response of non-gravid rat uterine smooth muscle to oxytocics in vitro. The specificity of PPP as a prostaglandin antagonist could therefore be species/tissue dependent.

Mitogen-activated protein kinase inhibitors suppress prostaglandin F(2alpha)-induced myosin-light chain phosphorylation and contraction in iris sphincter smooth muscle.

The purpose of this study was to investigate the potential role of mitogen-activated protein (MAP) kinase in contraction by monitoring MAP kinase phosphorylation (activation) and contraction during agonist stimulation of cat iris sphincter smooth muscle. Changes in tension in response to prostaglandin F(2alpha), latanoprost, a prostaglandin F(2alpha) analog used as an anti-glaucoma drug, and carbachol were recorded isometrically, and MAP kinase activation was monitored by Western blot using a phosphospecific p42/p44 MAP kinase antibody. We found that treatment of the muscle with 2'-Amino-3'-methoxyflavone (PD98059) (10 microM), a specific inhibitor of MAP kinase kinase (MEK), inhibited significantly prostaglandin F(2alpha)- and latanoprost-induced phosphorylation and contraction, but had little effect on those evoked by carbachol. Prostaglandin F(2alpha) increased MAP kinase phosphorylation in a concentration-dependent manner with EC(50) value of 1.1 x 10(-8) M and increased contraction with EC(50) of 0.92 x 10(-9) M. The MAP kinase inhibitors PD98059, Apigenin and 1,4-Diamino-2,3-dicyano-1, 4bis(2-aminophenylthio)butadiene (UO126) inhibited prostaglandin F(2alpha)-induced contraction in a concentration-dependent manner with IC(50) values of 2.4, 3.0 and 4.8 microM, respectively. PD98059 had no effect on prostaglandin F(2alpha)- or on carbachol-stimulated inositol-1,4,5-trisphosphate (IP(3)) production. In contrast, the MAP kinase inhibitor inhibited prostaglandin F(2alpha)-induced myosin-light chain (MLC) phosphorylation, but had no effect on that of carbachol. N-[2-(N-(4-Chloro-cinnamyl)-N-methylaminomethyl)phenyl]-N-[2- hydroxyethyl]-4-methoxybenzenesulfonamide (KN-93) (10 microM), a Ca(2+)-calmodulin-dependent protein kinase inhibitor, and Wortmannin (10 microM), an MLC kinase inhibitor, inhibited significantly (by 80%) prostaglandin F(2alpha)- and carbachol-induced contraction. It can be concluded that in this smooth muscle p42/p44 MAP kinases are involved in the mechanism of prostaglandin F(2alpha)-, but not in that of carbachol, induced contraction. In addition, these data clearly indicate that the stimulation of the iris sphincter with prostaglandin F(2alpha) and carbachol activate two distinct pathways, the MAP kinase pathway and the Ca(2+) mobilization pathway.

Uterotonic properties of the methanol extract of Monechma ciliatum.

The oxytocic activity of the hot methanol extract (HME) of the leaves of Monechma ciliatum was compared with other uterine stimulants like ergometrine, oxytocin, 5-hydroxytryptamine (5-HT), acetylcholine (ACh) and prostaglandins (PGs) E2 and F2alpha (PGE2 and PGF2alpha) in the presence of some antagonists in an attempt to explain the mechanism of action of the extract. The effects of the reference drugs on uteri isolated from rats pretreated with HME for 2 weeks were also observed. Atropine blocked the effect of ACh and partially blocked those of HME while L-366-948 blocked only the effect of oxytocin. Indomethacin inhibited the effects of HME as well as all the other drugs, except the PGs and ACh. D-600 blocked the effect of all the drugs including HME. Methysergide antagonised only the effect of 5-HT and partially blocked ergometrine. Prolonged treatment altered the uterine musculature and the activity profile of the reference drugs. These results suggest that the HME may be acting by more than one mechanism to contract the uterus and explains the mechanism of the anti-implantation activity of the plant.

Management of methylergonovine induced respiratory depression in a newborn with naloxone.

INTRODUCTION: We report a case of a female neonate who developed respiratory depression following the unintentional administration of methylergonovine. The respiratory depression appeared to improve after the administration of bag mask ventilation, stimulation, and naloxone; and the baby was able to be managed without endotracheal intubation and prolonged positive-pressure ventilation. CASE: A full-term female neonate was delivered vaginally without issue. Approximately 10 min after delivery, the infant was inadvertently administered 0.1 mg of methylergonovine intramuscularly instead of vitamin K. Thirty minutes later the child developed cyanotic extremities and respiratory depression with an oxygen saturation of 75%. Naloxone, 0.4 mg IM, was recommended to mitigate respiratory depression. Within 5 min the patient's respirations improved to 40 breaths per minute, cyanosis improved, and she began resisting ventilations and crying loudly. The child continued to improve and was back to baseline that evening. DISCUSSION: Methylergonovine toxicity in neonates has been commonly associated with respiratory depression necessitating ventilatory support. In consideration of chemical structural similarity between methylergonovine and morphine, as well as signs/symptoms consistent with opioid-induced respiratory depression, naloxone was suggested. CONCLUSION: It appears that naloxone may reverse methylergonovine toxicity in neonates. The identification of a safe and potentially useful antidote to mitigate respiratory depression, potentially avoiding the need for intubation and more invasive interventions in this patient population is important.

Erythromycin inhibits prostaglandin F2alpha-induced contractions of myometrium isolated from non-pregnant rats.

OBJECTIVE: The aim of this study was to investigate the effects of erythromycin on prostaglandin F2alpha (PGF2alpha)-induced contractions of isolated myometrial strips from non-pregnant rats. DESIGN: In vitro pharmacological study. SETTING: Firat University Faculty of Medicine. SAMPLE: Myometrium samples were taken from 55 adult Wistar rats. METHODS: Myometrial strips were isolated from mature, non-pregnant Wistar rats. Isometric contractions of these strips were induced with 1 microM PGF2alpha. Effects of 0.01, 0.1, 0.2, 0.5 and 1 mM erythromycin on the frequency and amplitude of these PGF2alpha-induced contractions were recorded. MAIN OUTCOME MEASURES: The inhibition of prostaglandin F2alpha-induced contractions in vitro. RESULTS: Application of 0.01 mM erythromycin had no effect on either amplitude or frequency of contractions. However, 0.1, 0.2, 0.5 and 1 mM erythromycin decreased the frequency and amplitude of PGF2alpha-induced contractions. The inhibitory effect of erythromycin on amplitude was 27%, 38%, 54% and 83% (P < 0.05), and that on frequency was 10%, 16%, 32% and 61% (P < 0.05) at 0.1, 0.2, 0.5 and 1 mM concentrations, respectively. CONCLUSION: The results of this study demonstrate that erythromycin inhibits PGF2alpha-induced contractions in rat myometrium. Because PGF2alpha-induced contractions have been suggested to be involved in the pathogenesis of primary dysmenorrhoea, effects of erythromycin in this clinical entity may present a new approach for the treatment.

Inhibitory effect of 2,5-dimethylpyrazine on oxytocic agent-induced uterine hypercontraction of normal or pregnant female rats.

Intraperitoneal administration of 2,5-dimethylpyrazine (2,5-DMP) was found to inhibit oxytocin- and prostaglandin F2alpha-induced tetanic uterine contractions in normal or pregnant female rats. This suggests that 2,5-DMP may be used as a countercontraction agent or relaxant for preventing oxytocic agent-induced medical accident including uterine rupture or pressure death of the fetus due to uterine contractions.

Prostaglandin-induced protection of cultured rat gastric cells against ethanol is inhibited by a microtubule inhibitor.

Prostaglandins reduce damage by noxious agents to isolated gastric cells. The mechanism remains unexplained. This study was done to examine involvement of microtubules with prostaglandin-mediated cell protection. Cultured mucus-producing cells of rat gastric mucosa were used. Cultured cells were incubated with 16, 16-dimethyl-prostaglandin E2 (dmPGE2), colchicine, or vehicle alone in calcium-containing (1.3 mM) and calcium-free medium. The cells were then exposed to 8% ethanol. Cell integrity and damage were assessed by 51Cr release and in part by transmission electron microscopy (TEM). Specific 51Cr release was closely related to percentage change of necrotic cells assess by TEM. Cell damage caused by 8% ethanol was greater in medium-containing calcium than in calcium-free medium. dmPGE2 at 10(-5) M inhibited cell damage in calcium-containing medium. Colchicine itself at concentrations up to 10(-5) M did not affect cell integrity, but at 10(-5) M concentration potentiated damage caused by 8% ethanol in calcium-containing medium. Pretreatment with 10(-5) M colchicine abolished the protective effect of dmPGE2. Microtubules may mediate protection by dmPGE2 of cultured gastric cells against ethanol damage.

The development and introduction of anti-oxytocic tocolytics.

The perfect tocolytic agent, which is completely safe for both the mother and fetus and, which will inhibit uterine contractions and stop preterm labour in every case does not exist and the search continues. Recently, research into a new group of tocolytic agents (the oxytocic antagonists) has led to the introduction of a new licensed drug, atosiban. Since the early 1950s, modifications of the oxytocin molecule have resulted in many analogues and antagonists, though initially none emerged as potentially useful drugs. Further modifications resulted in full uterotonic antagonism in animal models before an analogue was found that inhibited vasopressin-stimulated uterine contractions in non-pregnant healthy women. In vitro and animal models suggested the molecule was fully antagonistic, although it was found to be only partially agonistic in women. Further developments led to two modified oxytocin molecules with higher receptor affinity for human myometrium, both of which lacked agonism in humans. The analogue, atosiban, was found to be more potent and so was chosen for clinical evaluation in dysmenorrhoea and preterm labour. The first clinical reports were open label, observational pilot studies. Randomised, double-blind, phase II placebo-controlled studies followed showing that atosiban was significantly more effective than placebo with very few side effects. Dose-response studies and phase III studies in which study or placebo groups could use alternative tocolytic agents also suggested that atosiban was an effective tocolytic agent with very few adverse events. The recent worldwide comparative study of atosiban versus different beta-agonists represents the largest and most strictly controlled study of tocolytics ever published. Atosiban was found to be at least as effective as the beta-agonists as a tocolytic agent, but significantly less likely to result in maternal cardiovascular side effects or the need to discontinue therapy as a result of unacceptable side effects.

Action of pregnane compounds from Mandevilla illustris against contractions induced by kinins and other oxytocics in the rat isolated uterus.

1. The effects of 5 pregnane compounds isolated from the rhizomes of Mandevilla illustris were examined against bradykinin (BK), Lysyl-bradykinin (L-BK), acetylcholine (ACh) and oxytocin (Ot)-induced contractions in the isolated uteri of the rat. 2. Compounds MI 15 and MI 18 (5-40 micrograms/ml) caused a parallel and concentration-dependent rightward displacement of BK and L-BK concentration-response curves. Compound MI 21 (2.5-10 micrograms/ml) also produced a concentration-dependent displacement to the right of the BK concentration-response curve, but reduced its maximal response. Schild analysis of these data were linear (r close to 1) and furnished the following PA2 values (as G/ml): 6.0, 5.1 and 5.9, respectively. However, the slopes were significantly higher than unity. Compounds MI 25 and MI 27 (10-40 micrograms/ml) caused little or even no effect against BK and ACh responses. 3. In addition, compounds MI 18 and MI 21 (10-40 micrograms/ml) also antagonized in a concentration-dependent manner L-BK concentration-response curves. Schild plot were linear (r close to 1) and yielded the nominal pA2 values (as G/ml) of 5.0 and 5.8, respectively, but the slopes were significantly different from one. 4. Like the results obtained previously with the crude extract from M. illustris, the purified compounds from the rhizome of this plant were not selective towards kinin action since at the same range concentrations they markedly interfered with both the sensitivities and the maximal responses caused by ACh and Ot in this preparation.

Expression of low-molecular-weight kininogen mRNA in human fibroblast WI38 cells.

Expression of the low-molecular-weight kininogen (L-kininogen) mRNA in the human fibroblast cell line WI38 was examined by means of the reverse-transcription polymerase chain reaction and Southern blotting using human L-kininogen cDNA as a probe. The results demonstrated that WI38 fibroblasts expressed L-kininogen mRNA and that the expression was stimulated by 1 mM dibutyryl cAMP or 10 microM prostaglandin E2. Dexamethasone (1 microM) inhibited the stimulatory effect of prostaglandin E2. These results suggest that human fibroblasts supply L-kininogen, a protein precursor of the inflammatory mediator kinins, to connective tissues in response to inflammatory stimuli and that glucocorticoids may exert the antiinflammatory effect in part by inhibiting the local production of L-kininogen.