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At least 19 recordsLinked to original sources
PubMed1959

The effect of oxytocics on the "Ca-deficient" uterus. A measure of oxytocic potency.

If the excised, parturient rabbit uterus is repeatedly treated with a Krebs solution free from Ca, its tension in a tetanus drops gradually, and in 15 to 30 minutes becomes zero. We call such a uterus "Ca-deficient." The uterus in this condition has a high threshold, it is non-propagating, "inexcitable," fails to respond to oxytocics in a characteristic fashion, but retains maximum contractility. As Ca is gradually restored to the Krebs, these lost qualities return in a graded fashion and tension of the tetanized uterus becomes a log function of the [Ca]. If the [Ca] is kept low, i.e. 1/10 to 1/20 of the normal, tetanic tension is small but steady, and the preparation offers a full scale of tension increment for the measurement of oxytocic potency. Keeping the stimulus and the [Ca] constant, excitability (measured by tension increment) is a log function of the drug concentration. The recovery of excitability by restoring Ca to the Ca-deficient uterus is strongly temperature-dependent. The Ca-deficient uterus is a useful preparation for the study of the mechanism of regulation. When its excitability is partially recovered by Ca, the electrically stimulated uterus becomes an excellent tool for the quantitative measurement of oxytocic potency.

Animals↗
PubMed1995

Oxytocics in developing countries.

OBJECTIVES: A prospective multicenter study of obstetric practices was conducted in three developing countries (Benin, Congo and Senegal) to analyze oxytocic use during labor. One of the objectives was to assess the possible negative effects of the treatment regimens instituted during the labor monitoring phase. METHODS: Four health districts participated in the study. All women who gave birth in one of the participating health facilities over a 6-month period in Benin and Congo, and over a 3-month period in Senegal, were recruited. The number of deliveries studied in each district varied from 457 to 1048. For each case a partogram was used to assess the progress of labor and the onset of dysfunctional labor. Information was collected on the risk factors for dysfunctional labor, stillbirths and resuscitation of the neonate. RESULTS: Each of the four collaborating centers used oxytocics preferentially to treat dysfunctional labor, but even in normal labor (i.e. with a normal partogram) oxytocics were used in 4.4-21.5% of cases. In normal labor the incidence of neonatal resuscitation was higher in cases with than in those without oxytocic use: the relative risks (R.R.) varied from 1.9 to 5.6; the odds ratios varied from 2.4 to 7.0, and both were statistically significant in the four settings. In addition the stillbirth rate was always higher, though not significantly, when oxytocics were used in normal labor (R.R. 1.2-2.2). When the data of the four centers were pooled, the global relative risk for stillbirths was 1.9, and the 95% confidence interval was 1.1-3.4. Logistic regression analysis was carried out for five confounding factors (primiparity, a previous complicated delivery, presence of meconium, ruptured membranes and educational level) to adjust the odds ratio for the risk of neonatal resuscitation when oxytocics were used in normal labor. Except in the case of Abomey in Benin, where the variable 'presence of meconium' decreased the odds ratio from 6.4 to 3.4, the adjusted odds ratios remained similar to their non-adjusted values. In cases of non-dysfunctional labor, nurses and midwives used oxytocics more often than lesser trained health personnel (R.R. 4.0 [3.2-5.1]). CONCLUSION: Our results show that an obstetric treatment which is safe when used in certain well-defined indications, may have significant negative effects when used in situations where the same technical quality of care cannot be guaranteed.

Developing Countries↗
PubMed1976

Synthesis and some pharmacological properties of [1-(L-2-hydroxy-3-mercaptopropanoic acid), 4-threonine]oxytocin (hydroxy [4-thr]oxytocin), a peptide with strikingly high oxytocic potency and of [1-(L-2-hydroxy-3-mercaptopropanoic acid)]oxytocin (hydroxy-oxytocin).

[1-(L-2-Hydroxy-3-mercaptopropanoic acid), 4-threonine]oxytocin (hydroxy[4-Thr]oxytocin) and [1-(l-2-hydroxy-3-mercaptopropanoic acid)]oxytocin (hydroxy-oxytocin) were synthesized by a combination of solid phase and classical methods of peptide synthesis. Protected octapeptides were synthesized by the solid-phase method and 1 + 8 couplings in solution were then employed to furnish the required key protected intermediates. Hydroxy[4-Thr]oxytocin has oxytocic potency as measured in the rat uterus suspended in a Mg2+-free solution, of about 4200 units/mg, eight times the potency of oxytocin, while its antidiuretic potency is approximately equal to that of oxytocin. It thus exhibits a significantly favorable oxytocic-antidiuretic sleectivity. Hydroxy-oxytocin has an oxytocic potency of approximatels 1300 units/mt, 2.5 times that of oxytocin. Threonine substitution in hydroxy-oxytocin has thus caused a significant enhancement in both oxytocic potency and selectivity. The enhancement in oxytocic potency of these two peptides relative to oxytocin and [4-Thr]oxytocin appears to correlate with their lipophilic characteristics, suggesting a significant role of lipophilicity in the interplay of oxytocin-like peptides with oxytocic receptors.

Animals↗
PubMedDate not supplied

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.

Animals↗
PubMed1977

Synthesis and some pharmacological properties of [4-threonine, 7-glycine]oxytocin, [1-(L-2-hydroxy-3-mercaptopropanoic acid), 4-threonine, 7-glycine]oxytocin (hydroxy[Thr4, Gly7]oxytocin), and [7-Glycine]oxytocin, peptides with high oxytocic-antidiuretic selectivity.

[4-Threonine, 7-glycine]oxytocin and [1-(L-2-hydroxy-3-mercaptopropanoic acid), 4-threonine, 7-glycine]oxytocin (hydroxy[Thr4, Gly7]oxytocin) were synthesized by a combination of solid-phase and classical methods of peptide synthesis. A protected octapeptide was synthesized by the solid-phase method and following ammonolysis and purification 1 + 8 couplings in solution were employed to furnish the required key nonapeptide and acyl octapeptide intermediates, respectively. [7-Glycine]oxytocin was prepared from a sample of the protected nonapeptide intermediate used in the original synthesis of this peptide. [7-Glycine]oxytocin has an oxytocic potency (O) of 93 +/- 4 units/mg and an antidiuretic potency (A) of 0.0056 +/- 0.0003 units/mg. It has an O/A ratio of 16 000. [4-Threonine, 7-glycine]oxytocin has an oxytocic potency of 166 +/- 4 units/mg and an antidiuretic potency of 0.002 +/- 0.0004 units/mg. Its O/A ratio is 83 000. Threonine substitution has thus brought about a substantial enhancement in oxytocic activity and a fivefold enhancement in O/A selectivity. Hydroxy [Thr4, Gly7]oxytocin has an oxytocic potency of 218 +/- 8 units/mg and antidiuretic potency of 0.0040 +/- 0.0005 units/mg. Its O/A ratio is thus 54 500. All three 7-glycine-substituted analogues exhibit a marked sensitivity to Mg2+ on the rat uterus assay ststem and in the presence of 0.5 mM Mg2+ had oxytocic potencies in the range of 900-1000 units/mg. Should these peptides exhibit enhanced oxytocic selectivity in humans, they might offer a greater margin of safety than oxytocin in those clinical stiuations in which the latter is currently employed.

Amino Acids, Sulfur↗
PubMedDate not supplied

Plasma oxytocic activity after ovariectomy and stilboestrol or progesterone implantation in female rats.

Plasma oxytocic activity after ovariectomy and stillboestrol or progesterone implantation in female rats. Acta Physiol. Pol. 1977, 28 (2): 135--142. The purpose of this work was to compare the oxytocic activity of plasma in the intact rats, after ovariectomy, and in ovariectomized rats after subcutaneous implantation of stilboestrol or progesterone tablets. On the 22nd day after ovariectomy and implantation of hormones 2 ml of blood were obtained under urethane anaesthesia from the cephalad portion of the right external jugular vein. Plasma oxytocic activity was determined by the method of Van Dongen and Hays in Fragments of the rat mammary tissue at the time of lactation. The plasma oxytocic activity of ovariectomized female rats did not differ significantly from that found in the rats with implanted hormones. Cytological analysis of vaginal smears demonstrated stimulation of vaginal epithelium by exogenous hormones which lasted up to 10 days after implantation. Ovariectomy caused a threefold rise in the plasma oxytocic activity as compared with the control values.

Animals↗
PubMed1999

Bioassay-directed isolation of oxytocic principles from the methanol extract of Monechma ciliatum.

The hot methanol extract (HME) of Monechma ciliatum which has been reported to have potent oxytocic activity was purified by fractionation in an attempt to isolate the oxytocic principle. Thin layer analysis indicated that the oxytocic fraction was very polar. A positive reaction with ninhydrin-spray suggested that it is an amino acid/protein. Repeated column chromatography (CC) on silica gel followed by sephadex LH-20 column, accompanied by bioassay of the fractions on the rat isolated uterus enabled partial isolation of the oxytocic principle (P3) to be achieved. Although the exact structure of P3 could not be identified from the present study, various spectral analyses suggest that it is a small peptide made up of tyrosine, leucine and a third component which is probably serine. It is interesting to note that the parent compound, oxytocin, is also a peptide with tyrosine and leucine in its structure.

Animals↗
PubMed2004

Oxytocic activity of thrombin: modulation of thrombin-induced gravid rat myometrial contractions by 5-hydroxytryptamine receptor antagonists.

BACKGROUND: Thrombin possesses potent oxytocic activity in vitro and in vivo. This activity has been proposed to play a role in post-parturitional uterine contractions and possibly, preterm birth related to intrauterine hemorrhage. Previous workers have demonstrated that cyclo-oxygenase pathway may not play a significant role in oxytocic activity of thrombin. However, the role of 5-hydroxytryptamine (a mediator of some of the biological activities of thrombin) in the oxytocic activity of thrombin is unknown. The present study therefore aimed to examine the possible involvement of 5-hydroxytryptamine in thrombin-induced myometrial contractions. METHODS: Effect of 5-hydroxytryptamine receptor antagonists on thrombin-induced contractions of isolated gravid rat myometrium was studied using isolated tissue bath system. RESULTS: Thrombin-induced myometrial contractions were significantly and concentration-dependently inhibited by ketanserin and methysergide. Furthermore, 12 +/- 2% increase in the force of contractions of gravid rat myometrium pre-contracted with 5-hydroxytryptamine (1 microM) was provoked by 1 U/ml of thrombin. Thrombin-induced augmentation of the uterine stimulating effect of 5-hydroxytryptamine was characterized by pronounced increase in the contractile tone. CONCLUSIONS: 5-hydroxytryptamine may possibly play a role in oxytocic activity of thrombin. Uterine hyperactivity associated with intrauterine hemorrhage could hence involve thrombin-induced 5-hydroxytryptamine production in the uterus.

Animals↗
PubMed1988

Plasma levels of immunoreactive mesotocin and vasotocin during oviposition in chickens: relationship to oxytocic action of the peptides in vitro and peptide interaction with myometrial membrane binding sites.

Plasma concentrations of immunoreactive vasotocin (AVT) and mesotocin (MT) were measured periodically before and subsequent to spontaneous oviposition in conscious chickens. The concentrations of AVT and MT approximately an hour prior to oviposition were 5.2 +/- 1.1 microU/ml and 14.7 +/- 5.1 pg/ml, respectively. Plasma AVT levels increased abruptly at oviposition (25.1 +/- 3.3 microU/ml) and decreased to 5.0 +/- 0.6 microU/ml within 30 min postoviposition. Significant changes in MT were not observed. The data indicate that AVT is selectively released during oviposition. The uterus was removed immediately after oviposition and the oxytocic potencies of several peptides were tested on muscle strips in vitro. The order of oxytocic potencies was AVT greater than or equal to arginine vasopressin (AVP) much greater than MT = pressinoic acid. Partially purified membranes were prepared from separate portions of the uteri used in the oxytocic assay. [3H]arginine8 vasopressin, [3H]AVP, bound to membranes saturably (Bmax = 17 fmol/mg protein) and with high affinity (Kd = 0.7 nM). The rank order of potency of the peptides in displacing [3H]AVP from the binding sites was the same as in the oxytocic assay which suggests that the [3H]AVP binding sites in uterine membranes represent physiological receptors that interact with AVT during oviposition.

Animals↗
PubMed1994

Comparison of binding affinity of oxytocin antagonists to human and rat uterine oxytocin receptors and their correlation to the rat uterine oxytocic bioassay.

One of the primary methods used to screen the development of oxytocin antagonists (OTAs) is the rat oxytocic bioassay. The purpose of this study was to determine whether the rat oxytocic bioassay is a good predictor of binding affinity to human and rat uterine oxytocin receptors (OTr). The binding affinities of five OTAs to human and rat uterine OTr were determined and correlated with pA2 values derived from the rat uterine oxytocic bioassay. Human uterine myometrial tissue was obtained from patients at the time of cesarean section. Rat uterine tissue for the OTr assay was taken at Day 21 of pregnancy. OTr assays were accomplished by isolating uterine cell membranes and performing saturation analysis with cold OTAs and tritium-labeled oxytocin. The association constants (Ka; 10(+8)/M) were calculated by nonlinear curve-fitting techniques. The Ka for the five OTAs (Mpa1-OT, Antag I, L366948, Antag II, and Antag III), as estimated from the human OTr assay, were 0.55, 0.60, 2.27, 1.91, and 47.20, respectively. Ka estimates obtained through use of rat uterine membranes were 0.51, 1.16, 5.89, 2.03, and 24.40, respectively. Correlation of the log10 of the rat oxytocic bioassay results with those of the rat and human OTr assay was 0.94 and 0.98, respectively (p < 0.01). Antag III was approximately 55, 48, and 90 times more potent than Mpa1-OT as determined by the rat bioassay and rat and human uterine OTr assays, respectively. Mpa1-OT is an OTA that is currently undergoing clinical evaluation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

The effects of routine oxytocic administration in the management of the third stage of labour: an overview of the evidence from controlled trials.

Recent claims that routine active management of the third stage of labour increases rather than decreases maternal and neonatal morbidity have prompted us to conduct a systematic review of the relevant controlled trials. In this paper we have analysed data derived from a total of nine published reports of controlled trials in which an oxytocic drug was compared with either a placebo or no routine prophylactic. Oxytocic drugs used routinely appear to reduce the risk of postpartum haemorrhage by about 40% (typical odds ratio 0.57, 95% confidence interval 0.44-0.73) implying that for every 22 women given such an oxytocic, one postpartum haemorrhage could be prevented. The available data are insufficient to assess the possible effects of this policy on the incidence of retained placenta, hypertension and other possible adverse effects.

Clinical Trials as Topic↗
PubMed1990

Effect of oxytocics on prostaglandin levels in the third stage of labour.

The levels of prostaglandin F2 alpha metabolites (PGFM) in the peripheral blood were measured during third stage in a group of patients not given any oxytocic and this was compared with the levels produced in other groups given different oxytocics. There was a significant rise in PGFM within 5 min of delivery in all groups but there was no statistical difference in the serum concentrations of PGFM between the different groups. This suggests that oxytocics given during third stage do not act through release of prostaglandins.

Adult↗
PubMed1986

[A basic study of the oxytocic effect of prostacyclin on the uterine muscle in pregnant rats].

The effects of prostacyclin (PGI2) on the uterine muscle of pregnant rats were studied in terms of uterine contraction and the variation in cyclic nucleotides. The following results were obtained: The administration of PGI2 stimulated the pregnant uterine muscle (in vitro). The oxytocic potency of PGE1-analog (ONO-802) was greatest, followed in order by that of PGF2 alpha and PGI2. The effect of 5-lypoxygenase inhibitor (AA-861) on uterine contraction was greatest under the administration of LTC4, followed in order by PGI2, oxytocin, PGF2 alpha, LTD4 and ONO-802. The effect of AA-861 was greater under the simultaneous administration of LTD4/LTC4 and ONO-802 than under the simultaneous administration of oxytocin and ONO-802. Terbutaline exerted the inhibitory effect on each of the oxytocies within two minutes in all cases. Its inhibitory effect on the oxytocics was slight in the cases to which oxytocin or ONO-802 was administered. Changes in cyclic nucleotides in the bath medium were determined before and after the administration of each drug. When PGI2 was administered, both c-AMP and c-GMP increased and showed a pattern which was different from that for other oxytocics. This tendency was also observed when PGI2 and other drugs (terbutaline, ONO-802 and AA-861) were administered together.

Alprostadil↗
PubMed1985

Relative oxytocic properties of fenprostalene compared with cloprostenol, prostaglandin F2 alpha, and oxytocin in the ovariectomized ewe.

The oxytocic effect of a prostaglandin F2 alpha analogue, fenprostalene, was assessed in 4 ovariectomized ewes fitted with electrodes in both uterine horns and in the cervix. In the absence of estradiol priming, significant motility changes were not elicited by fenprostalene. Conversely, when ewes were primed with 17-beta-estradiol, fenprostalene markedly increased the electrical activity in the uterus and cervix. After a single subcutaneous fenprostalene administration (5 micrograms/kg), activity values remained about twice that of the control values during 8.52 +/- 3.31 hours. When the same dosage was administered IM, similar post-injection activity values were obtained, but only during 5.88 +/- 0.72 hours. Oxytocic effects of fenprostalene were far longer than those elicited by a single IM administration of 50 micrograms of prostaglandin F2 alpha (tham salt)/kg (0.91 +/- 0.32 hours) or by a single IM administration of 1 microgram of cloprostenol/kg (1.88 +/- 0.81 hours). Using the dose-effect relationship curve obtained from the same ewes by continuous IV infusions of oxytocin (OXT), the postinjection activity values reached after a single subcutaneous administration of fenprostalene were equivalent to those of an IV infusion of OXT at an average dose of 4.09 ImU of OXT/kg/hr for 6 to 13 hours, according to the values of the particular ewe concerned. These long-lasting oxytocic properties, in addition to its luteolytic capabilities, would make fenprostalene a suitable drug for promoting effective evacuation of the uterus when required in daily veterinary practice.

Abortifacient Agents↗
PubMed1998

[Parturients are under-treated. Only 21 out of 55 clinics administer oxytocics routinely during the third stage of labor].

A questionnaire answered by all 55 Swedish labour wards in 1995 showed oxytocic treatment to be given routinely to all parturients during the third stage of labour at only 38% (21/55) of the units, and that five of these 21 units were considering cessation of the practice. At a further 25 units the treatment was given routinely only in selected risk cases, the most common risk factors being a history of postpartum haemorrhage (a criterion at 20 units), multiple pregnancy (14 units), prolonged labour (12 units), and a large baby (8 units). Of the remaining nine units, where oxytocic treatment was given only on clinical indications (i.e., postpartum haemorrhage), two were considering the introduction of routine treatment. In view of results obtained in a recent randomised, placebo controlled Swedish study, the authors of the article conclude that, if clinical practice in this respect has remained unchanged since the questionnaire study was performed, Swedish parturients are undertreated with oxytocics during the third stage of labour.

Female↗