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PubMed1993

[Delivery after 2 previous cesarean sections. A series of 41 uterine trials].

It has been possible to consider how delivery should be carried out in view of the progress that has been made handling scarred uteruses. Over 21 months 41 tests of uterine function have been authorized in our department out of 67 cases where there were two scars in the uterus (67%). 26 patients delivered vaginally (63.4%) and 5 had Caesarean sections because of failure of the test of the scar. When the relationship between the fetus and the pelvis was satisfactory, the fact that the cervix was not ripe and the presenting part was not engaged, did not prevent carrying out a trial of scar in 78% of cases. It is important to assess conditions continuously during labour and this assessment should include fetal heart monitoring, internal tokometry, fetal pH assessment and ultrasound of the scar at the onset of labour. Oxytocics had to be used in 96.2% of cases because there was at the outset marked dynamic dystocia. Epidural anaesthesia was used in 90.2% of cases. A full obstetric team must be present throughout the whole labour so that the conduct of the labour can be observed, and if necessary corrected quickly if anything in its progress is becoming abnormal. It has become reasonable to carry out tests of uterine scars even after two scars have been made in the uterus because of the absence of any maternal or fetal complications in this series or in the literature.

Anesthesia, Epidural↗
PubMed1995

An analysis of risk factors for the prediction of shoulder dystocia in 16,471 consecutive births.

This paper is a univariate analysis of the demographic, antepartum and intrapartum risk factors in a series of 16,471 consecutive deliveries in a tertiary obstetric and gynaecological unit in Singapore. In total, 12,229 term vaginal cephalic deliveries with 77 cases of shoulder dystocia were entered into the study for analysis. The incidence of shoulder dystocia was found to be 0.63% of all term vaginal cephalic deliveries. There is a direct relationship between increasing infant birthweight and incidence of shoulder dystocia. The critical birthweight for the prediction of shoulder dystocia is 3600 g. In order of decreasing relative risks, the factors which appear to be predictive of shoulder dystocia are a birthweight in excess of 3600 g, diabetes in pregnancy, lower social class, of Indian origin, maternal weight in excess of 70 kg, parity more than 4, and the use of oxytocics during labour. The local birthweight distribution is very different from the West. A policy for elective caesarean section for birthweights in excess of 4000 g (97% tile) would prevent 44% of shoulder dystocias, increase the caesarean section rate by 2% and half the perinatal mortality among births with shoulder dystocia.

Adult↗
PubMedDate not supplied

Double-blind, randomized comparison of the effect of carbetocin and oxytocin on intraoperative blood loss and uterine tone of patients undergoing cesarean section.

OBJECTIVES: A double-blind randomized study involving pregnant women undergoing cesarean section was conducted to compare the effectiveness of a single 100 micrograms intravenous injection of the long-acting oxytocin analog, carbetocin, with that of a standard infusion of oxytocin with respect to intraoperative blood loss. The two treatments also were compared for safety and ability to maintain adequate uterine tone. STUDY DESIGN: The study drug was administered to 57 women during elective cesarean section after placental delivery; blood was collected until abdominal closure. Intraoperative blood loss was calculated with a sensitive colorimetric method. Position, tone of the fundus, and vital signs were assessed up to 24 hours after the operation. The need for additional uterotonic agents was recorded. RESULTS: A single 100 micrograms intravenous injection of carbetocin was as effective as a continuous 16 hour infusion of oxytocin in controlling intraoperative blood loss after placental delivery. Mean blood loss after carbetocin administration was 29 ml less than after oxytocin administration (p = 0.3). Subset analysis deleting two patients who received oxytocic intervention in the operating room and one extreme outlier revealed a mean blood loss of 41 ml less in the carbetocin group (p = 0.14) with lower variances (p = 0.02). The percentage of patients with blood loss of 200 ml or less was greater with carbetocin (79% vs 53%; p = 0.041). Carbetocin enhanced early postpartum uterine involution. The fundus was below the umbilicus in more patients who received carbetocin at 0, 2, 3, and 24 hours on the ward (p < 0.05). There were no significant differences in uterine tone or type or amount of lochia. Additional oxytocin was used to treat three patients for postpartum hemorrhage or persistent uterine atony. All interventions were in the oxytocin group. Vital signs and hematologic values were comparable in each group, confirming similar safety profiles. CONCLUSIONS: A single 100 micrograms intravenous injection of carbetocin is as effective and more reliable than a standard continuous infusion of oxytocin in maintaining adequate uterine tone and preventing excessive intraoperative blood loss during cesarean section after delivery of the placenta. Patients receiving carbetocin required less intervention. Carbetocin was well tolerated.

Adult↗
PubMedDate not supplied

Position three in vasopressin antagonist tolerates conformationally restricted and aromatic amino acid substitutions: a striking contrast with vasopressin agonists.

We report the solid-phase synthesis and some pharmacological properties of 12 position three modified analogues (peptides 1-12) of the potent non-selective antagonist of the antidiuretic (V2-receptor), vasopressor (V1a-receptor) responses to arginine vasopressin (AVP) and of the uterine contracting (OT-receptor) responses to oxytocin (OT), [1(-beta mercapto-beta,beta-pentamethylenepropionic acid)-2-O-ethyl-D-tyrosine 4-valine] arginine vasopressin [d(CH2)5D-Tyr(Et)2VAVP] (A) and two analogues of (B) (peptides 13,14), the 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid3 (Tic3) analogue of (A). Peptides 1-12 have the following substituents at position three in (A): (1) Pro; (2) Oic; (3) Atc; (4) D-Atc; (6) D-Phe; (7) Ile; (8) Leu; (9) Tyr; (10) Trp; (11) Hphe; (12) [HO]Tic; Peptide (13) is the Tyr-NH2(9) analogue of (B): Peptide (14) is the D-Cys(6) analogue of (B). All 14 new peptides were evaluated for agonistic and antagonistic activities in in vivo V2 and V1a assays and in vitro (no Mg2+)n oxytocic assays. With the exception of the D-Phe3 peptide (No. 6), which exhibits very weak V2 agonism (approximately 0.0017 U/mg), none of the remaining 13 peptides exhibit any agonistic activities in these assays. In striking contrast to their deleterious effects on agonistic activities in AVP, the Pro3, Oic3, Tyr3 and Hphe3 substitutions in (A) are very well tolerated, leading to excellent retention of V2, V1a and OT antagonistic potencies. All are more potent as V2 antagonists than the Ile3 and Leu3 analogues of (A). The Tyr-NH2(9) and D-Cys(6) substitutions in (B) are also well tolerated. The anti-V2 pA2 values of peptides 1-5 and 7-14 are as follows (1) 7.77 +/- 0.03; (2) 7.41 +/- 0.05; (3) 6.86 +/- 0.02; (4) 5.66 +/- 0.09; (5) approximately 5.2; (7) 7.25 +/- 0.08; (8) 6.82 +/- 0.06; (9) 7.58 +/- 0.05; (10) 7.61 +/- 0.08; (11) 7.59 +/- 0.07; (12) 7.20 +/- 0.05; (13) 7.57 +/- 0.1; (14) 7.52 +/- 0.06. All analogues antagonize the vasopressor responses to AVP, with anti-V1a pA2 values ranging from 5.62 to 7.64, and the in vitro responses to OT, with anti-OT pA2 values ranging from 5.79 to 7.94. With an anti-V2 potency of 7.77 +/- 0.03, the Pro3 analogue of (A) is surprisingly equipotent with (A), (anti-V2 pA2 = 7.81 +/- 0.07). These findings clearly indicate that position three in AVP V2/V1a antagonists, in contrast to position three in AVP agonists, is much more amenable to structural modification than had heretofore been anticipated. Furthermore, the surprising retention of V2 antagonism exhibited by the Pro3, Oic3, Tyr3, Trp3 and Hphe3 analogues of (A), together with the excellent retention of V2 antagonism by the Tyr-NH2(9) and D-Cys6 analogues of (B) are promising new leads to the design of potent and possibly orally active V2 antagonists for use as pharmacological tools and/or as radioiodinatable ligands and for development as potential therapeutic agents for the treatment of the hyponatremia caused by the syndrome of the inappropriate secretion of the antidiuretic hormone (SIADH).

Administration, Oral↗
PubMed1999

Synthesis and structure-activity investigation of novel vasopressin hypotensive peptide agonists.

We report the solid phase synthesis and vasodepressor potencies of the novel hypotensive peptide [1(-beta-mercapto-beta,beta-pentamethylene propionic acid)-2-O-ethyl-D-tyrosine, 3-arginine, 4-valine] arginine vasopressin, d(CH2)5[D-Tyr(Et)2, Arg3, Val4]AVP (A), its related Lys3 (B), Tyr-NH(9)2 (C), [Lys3, Tyr-NH(9)2 (D) analogs and in a preliminary structure-activity study of positions 2-4 and 7-9, 24 analogs (1-24) of A-C. Peptides 1-6, 9-14 have the following single substituents at positions 2, 3, 4, 8 and 9 in (A): 1, D-Tyr(Me)2; 2, L-Tyr(Et)2; 3, Orn3; 4, N-Me-Arg3; 5, Glu3; 6, Arg4; 9, D-Arg8; 10, Eda9; 11, Arg-NH(9)2; 12, Ala-NH(9)2; 13, desGly9; 14, desGly-NH(9)2. Peptides 15 and 16 are analogs of B which possess the following single modifications: 15, Arg-NH(9)2; 16, desGly9. Peptides 7 and 8 are analogs of (C) with the following single modification: 7, Gln4; 8, Lys8. Peptides 17-24 are analogs of A possessing the following multiple modifications: 17, [Sar7, Eda9]; 18, [Arg7, Eda9]; 19, [Arg7, Eda9<--Tyr10]; 20, [Arg4, Arg-NH(9)2]; 21, [Ile4, desGly9]; 22, [Arg4, desGly9]l; 23, [Arg7, desGly9]; 24, [Arg7, Lys8, desGly9]. All 24 new peptides were evaluated for agonistic and antagonistic activities in in vivo antidiuretic (V2-receptor), vasopressor (V1a-receptor) and in in vitro (no Mg2+) oxytocic (OT-receptor) assays and like the parent peptides (A-D) (Chan et al. Br. J. Pharmacol. 1998; 125: 803-811) were found to exhibit no or negligible activities in these assays. Vasodepressor potencies were determined in anesthetized male rats with baseline mean arterial blood pressure maintained at 110-120 mmHg. The effective dose (ED), in microg 100 g(-1) i.v., required to produce a vasodepressor response of 5 cm2, area under the vasodepressor response curve (AUC) during the 5-min period following the injection of the test peptide, was determined. Therefore, the EDs measure the relative vasodepressor potencies of the hypotensive peptides. The following ED values were obtained for A-D and for peptides 1-24: A, 4.66; B, 5.75; C, 10.56; D, 11.60; 1, approximately 20; 2, approximately 30; 3, 6.78; 4, non-detectable (ND); 5, ND; 6, approximately 32; 7, ND; 8, 8.67; 9, ND; 10, 2.43; 11, 3.54; 12, 10.57; 13, 4.81; 14, ND; 15, 4.47; 16, 9.78; 17, 5.72; 18, 1.10; 19, 1.05; 20, 10.41; 21, 9.13; 22, approximately 33; 23, 3.01; 24, 1.71. A is clearly the most potent of the four original hypotensive peptides A-D. These data provide insights to which modification of A enhance, retain or abolish hypotensive potencies. Six of the new hypotensive peptides are significantly more potent than A. These are peptides 10, 11, 18, 19, 23 and 24. Peptide 19, a radioiodinatable ligand, is ten times more potent than C or D. The Gln4 modification of C and the N-Me-Arg3, Glu3, D-Arg8 and desGly-NH(9)2 modifications of A abolished hypotensive potency. By contrast, the Eda9, Arg-NH(9)2, [Sar7, Eda9], [Arg7, Eda9<- -Tyr10], [Arg7, desGly9], [Arg7, Lys8, desGly9] modifications of A all led to enhancements of hypotensive potency. This initial structure-activity exploration provides useful clues to the design of (a) more potent vasodepressor peptides and (b) high affinity radioiodinatable ligands for the putative AVP vasodilating receptor. Some of the peptides here may be of value as pharmacological tools for studies on the complex cardiovascular actions of AVP and may lead to the development of a new class of anti-hypertensive agents.

Arginine Vasopressin↗
PubMed1999

Uterine muscle reactivity to repeated administration and phytochemistry of the leaf and seed extracts of Piper guineense.

The leaf and seed of Piper guineense were separately extracted and the effects of repeated treatments on rat uterine contractions and their chemical composition were investigated. Repeated treatments with the extracts enhanced spontaneous uterine muscle contractions in a dose related pattern for up to 14 days which was followed by a marked decrease in uterine response in those treated for 30 days. Similarly, the pretreatment with the extracts maximally enhanced oxytocin induced uterine contraction in those rats treated for 3 days, this was followed by a gradual reversal of the effect when treatment was repeated for up to 14 days. This enhanced uterine contraction was inhibited following treatment for 30 days. In a further study, treatment with the extracts induced a significant increase in the uterine weight similar to that seen with oestradiol. It is therefore concluded that the leaf and seed extracts of Piper guineense possess oestrogenic and oxytocic properties which might justify their usage in Nigerian traditional medicine.

Animals↗
PubMed1999

Effects of ethanol extract of Moringa stenopetala leaves on guinea-pig and mouse smooth muscle.

The fresh leaf ethanol (LE) extract of Moringa stenopetala was tested in guinea-pig ileum and mouse duodenum and in uterus strips. There were significant dose and time dependent reductions of the acetylcholine (AC) response with initial stimulatory effects in both the guinea-pig ileum and the mouse duodenum preparations. Spontaneous rhythmic contractions were greatly reduced, suggesting an antispasmodic property of the crude LE extract. The LE extract showed some oxytocic activity on uterus strips of guinea-pigs and mice. The results are indicative of the traditional use of the leaves of Moringa stenopetala for stomach pain and to expel retained placentae by women.

Animals↗
PubMed2005

Placental cord drainage after spontaneous vaginal delivery as part of the management of the third stage of labour.

BACKGROUND: Cord drainage in the third stage of labour involves unclamping the previously clamped and separated umbilical cord and allowing the blood from the placenta to drain freely into an appropriate receptacle. Currently there are no systematic reviews of the effects of placental cord drainage on the management of the third stage of labour. OBJECTIVES: The objective of this review was to assess the specific effects of placental cord drainage on the third stage of labour, with or without the prophylactic use of oxytocics. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group Trials register (July 2005), CINAHL (1982 to December 2004) and the National Research Register (December 2004). SELECTION CRITERIA: Randomised trials involving placental cord drainage as a variable within the package of interventions as part of the management of the third stage of labour. DATA COLLECTION AND ANALYSIS: Two review authors independently assessed the quality of trials and extracted data. MAIN RESULTS: Two studies met our inclusion criteria in terms of quality and relevance. Cord drainage could impact the third stage of labour as the results show a statistically significant reduction in the length of third stage of labour (one trial, n = 147, weighted mean difference (minutes) -5.46, 95% confidence interval (CI) -8.02 to -2.90). In the incidence of retained placenta at 30 minutes after birth (one trial, n = 477, relative risk 0.28, 95% CI 0.10 to 0.73) a significant difference was found, but this should be interpreted with caution due to potential intervention bias. AUTHORS' CONCLUSIONS: It is difficult to draw conclusions from such a small number of studies, especially where the review outcomes were presented in a variety of formats. However, there does appear to be some potential benefit from the use of placental cord drainage in terms of reducing the length of the third stage of labour. More research is required to investigate the impact of cord drainage on the management of the third stage of labour.

Constriction↗
PubMed1992

Changes in annexin (lipocortin) content in human amnion and chorion at parturition.

Arachidonic acid is mobilized from fetal membrane phospholipids at parturition leading to increased production of oxytocic prostaglandins which may initiate or maintain myometrial contractions. Phospholipid mobilization requires activation of phospholipase A2 or C, both of which require calcium for activity. The annexins (lipocortins) are a superfamily of proteins which bind to calcium and phospholipids and thereby may alter phospholipase activity through two mechanisms: modulation of intracellular free Ca2+ concentrations or regulation of the accessibility of phospholipids to hydrolyzing enzymes. Using Western immunoblotting with monospecific polyclonal antibodies, annexins I-VI were identified in human amnion and chorion/decidua at term in tissues obtained from patients in labor or not in labor. Each annexin was present in two distinct pools: a pool which only associated with the membrane in the presence of calcium (calcium-dependent pool) and a calcium-independent pool that remained membrane bound in the presence of calcium chelators. Annexin I was present as two species, resolving at 36 kDa and 68 kDa. The total concentration of annexin I in both amnion and chorion/decidua was significantly decreased with labor, while the total concentration of annexin V in chorion significantly increased with labor. The size of individual pools of annexins also changed with labor: the calcium-dependent pool of annexins I and II in both amnion and chorion significantly decreased; the calcium-dependent pool of annexin V increased in chorion; and calcium-independent pools of annexin I in amnion and annexins I, II, and V in chorion significantly decreased with labor. The decrease in total annexin I concentration with labor in amnion reflects a substantial decrease (80-90%) in the pool tightly bound to the membrane in a calcium-independent manner. This striking change distinguishes annexin I as a potential candidate inhibitor which is specifically downregulated at parturition, potentially leading to increased access of phospholipases to substrate phospholipids and increased prostaglandin production at labor.

Amnion↗
PubMed1995

Effects of annetocin, an oxytocin-related peptide isolated from the earthworm Eisenia foetida, and some putative neurotransmitters on gut motility of the earthworm.

Annetocin, an oxytocin-related peptide recently isolated from the lumbricid earthworm Eisenia foetida, and putative transmitter substances were examined for their effects on rhythmic, spontaneous contractions of isolated gut preparations of the earthworm. Significant, dose-dependent effects of the following substances were observed: acetylcholine (ACh), gamma-aminobutyric acid (GABA), and dopamine were excitatory, while serotonin (5-HT) and octopamine were inhibitory. Annetocin, oxytocin, and vasotocin stimulated spontaneous contraction of the earthworm gut, annetocin being approximately 10-fold more potent than oxytocin or vasotocin. However, arginine-vasopressin (Arg-vasopressin), lysine-vasopressin (Lys-vasopressin), tocinoic acid (N-terminal hexapeptide fragment of oxytocin), and MSH release-inhibiting factor (MIF; C-terminal tripeptide fragment of oxytocin) did not show any effect on the earthworm gut motility. On the other hand, oxytocin, vasotocin, Arg-vasopressin, Lys-vasopressin, and tocinoic acid caused spontaneous contractions of isolated rat uterine preparations, where the potency was in this order, while annetocin and MIF exerted no oxytocic activity on the uterus. Dose-response relationship of the effects of annetocin and its related peptides on the annelid and mammalian systems shows that amino acid residue at the third position of these peptides is important for exertion of excitatory action on the smooth muscle systems. The results in the present study suggest that receptors for annetocin and for GABA on the earthworm gut, unlike those for ACh, desensitize during continuous exposure to these substances.

Amino Acid Sequence↗
PubMed1976

Pharmacological assessment of 3-tert-butylsydnone.

The pharmacological effects of the mesoionic derivative, 3-tert-butylsydnone, were investigated. Administration to rats caused clonic convulsions. The CD50 of 3-tert-butylsydnone was 0.471 +/- 0.033 mmole/kg. Trimethadione, but not phenytoin sodium or proadifen hydrochloride, protected the rat from the effects of 3-tert-butylsydnone. After administration of this compound, pentobarbital sodium sleeping time was reduced in the rat, but blood pressure and ECG were unchanged in the dog. Pretreatment of the mouse with 3-tert-butylsydnone did not influence the LD50 of epinephrine hydrochloride. The action of methacholine chloride in the rat was not blocked, and the pupil of the rabbit eye was unaffected. Tests for analgesic and oxytocic activity were negative. Chronic administration of a small dose to the rat for 70 days had no effect on blood glucose, blood urea nitrogen, hemoglobin, or microhematocrit values.

Anesthesia↗
PubMed2001

Design of oxytocin antagonists, which are more selective than atosiban.

We report the solid phase synthesis of four pairs of L- and D-thienylalanine (Thi/D-Thi) position two modified analogues of the following four oxytocin (OT) antagonists: des-9-glycinamide [1-(beta-mercapto-beta,beta-pentamethylene propionic acid), 2-O-methyltyrosine, 4-threonine]ornithine-vasotocin (desGly(NH2)9,d (CH2)5[Tyr(Me)2,Thr4]OVT) (A); the Tyr-(NH2)9 analogue of (A), d(CH2)5[Tyr(Me)2,Thr4,Tyr-(NH2)9]OVT (B); the Eda9 analogue (where Eda = ethylenediamine) of (A), d(CH2)5[Tyr(Me)2, Thr4, Eda9]OVT (C); and the retro Tyr10 modified analogue of (C), d(CH2)5[Tyr(Me)2, Thr4, Eda9<--Tyr10]OVT (D). The eight new analogues of A-D are (1) desGly(NH2),d(CH2)5[Thi2,Thr4]OVT, (2) desGly(NH2),d(CH2)5[D-Thi2,Thr4]OVT, (3) d(CH2)5[Thi2, Thr4,Tyr-(NH2)9]OVT, (4) d(CH2)5[D-Thi2,Thr4,Tyr-(NH2)9]OVT (5) d(CH2)5[Thi2,Thr4Eda9]OVT, (6) d(CH2)5[D-Thi2,Thr4,Eda9]OVT, (7) d(CH2) [Thi2,Thr4,Eda9<--Tyr10]OVT, (8) d(CH2),[D-Thi2,Thr4,Eda9<--Tyr10]OVT. We also report the synthesis of (C). Peptides 1-8 and C were evaluated for agonistic and antagonistic activities in in vitro and in vivo OT assays, in in vivo vasopressor (V1a receptor) assays and in in vivo antidiuretic (V2 receptor) assays. None of the eight peptides nor C exhibit oxytocic or vasopressor agonism. Peptides 1-8 are extremely weak V2 agonists (antidiuretic activities range from < 0.0005 to 0.20 U/mg). Peptide C is a weak mixed V2 agonist/antagonist. Peptides 1-8 and C exhibit potent in intro (no Mg2+) OT antagonism (anti-OT pA2 values range from 7.76 to 8.05). Peptides 1-8 are all OT antagonists in vivo (estimated in vivo anti-OT pA2 values range from 6.54-7.19). With anti-V1a pA2 values of approximately 5-5.80, peptides 1-8 exhibit marked reductions in anti-V1a potencies relative to those of the parent peptides A-D (anti-V1a pA2 range from 6.48 to 7.10) and to l-deamino[D-Tyr(Et)2, Thr4]OVT (Atosiban, trade name Tractocile) (anti-V1a pA2-6.14). Atosiban has recently been approved in Europe for clinical use for the prevention of premature labour (Pharm. J. 264(7-100): 871). Peptides 1-8 exhibit striking gains in in vitro anti-OT/anti-V1a selectivities with respect to the parent peptides A, B, C and D and to Atosiban. Peptides 1-8 exhibit anti-OT (in vitro)/anti-V1a selectivities of 450, 525, 550, 450, approximately 1080, 116, 355, 227 respectively. The corresponding values for A-D and Atosiban are 30, 4.2, 4.3, 2.6 and 37. With the exception of peptide 6, the remaining seven peptides exhibit 3-18-fold gains in anti-OT (in vivo)/anti-V1a selectivity with respect to Atosiban, peptides 1-8 exhibit anti-OT (in vivo)/anti-V1a selectivities of 22, approximately 82, approximately 82, 147, approximately 83, 11, 31 and 42. By comparison, Atosiban exhibits an anti-OT (in vivo)/anti-V1a selectivity = 8. With an estimated in vivo anti-OT pA2 value = 7.19+/-0.06, peptide 4 is equipotent with Atosiban (pA2 = 7.05+/-0.05). However, with its significantly reduced anti-vasopressor potency, pA2 = approximately 5, it is approximately 18 times more selective for OT receptors with respect to VP V1a receptors than Atosiban. Since we have shown that V1a antagonism could be an unwanted side-effect in tocolytics, peptide 4 and some of the OT antagonists reported here have advantages over Atosiban and thus may be suitable candidates for evaluation as potential tocolytic agents for the treatment of preterm labour.

Biological Assay↗
PubMed2005

Design of peptide oxytocin antagonists with strikingly higher affinities and selectivities for the human oxytocin receptor than atosiban.

The peptide oxytocin (OT) antagonist atosiban, approved for tocolytic use in Europe (under the tradename Tractocile), represents an important new therapeutic advance for the treatment of premature labor. This paper presents some new peptide OT antagonists which offer promise as superior tocolytics. The solid phase synthesis is reported of four pairs of L and D-2-naphthylalanine (L/D-2Nal) position-2 modified analogs of the following four oxytocin (OT) antagonists: des-9-glycinamide [1-(beta-mercapto-beta,beta-pentamethylene propionic acid), 2-O-methyltyrosine, 4-threonine]ornithine-vasotocin (desGly-NH(2),d(CH(2))(5)[Tyr(Me)(2),Thr(4)]OVT) (A); the Tyr-NH(2) (9) analog of (A), d(CH(2))(5)[Tyr(Me)(2),Thr(4),Tyr-NH(2) (9)]OVT (B); the Eda(9) analog of (A), d(CH(2))(5)[Tyr(Me)(2),Thr(4),Eda(9)]OVT (C); and the retro COCH(2)Ph(4-0H)(10) modified analog of (C), d(CH(2))(5)[Tyr(Me)(2),Thr(4),Eda(9)<-- COCH(2)Ph(4-0H)(10)]OVT (D). The eight new analogs of A-D are (1) desGly-NH(2),d(CH(2))(5)[D-2Nal(2),Thr(4)]OVT, (2) desGly-NH(2),d(CH(2))(5)[2-Nal(2),Thr(4)]OVT, (3) d(CH(2))(5)[D-2Nal(2),Thr(4),Tyr-NH(2) (9)]OVT, (4) d(CH(2))(5)[2Nal(2),Thr(4),Tyr-NH(2) (9)]OVT, (5) d(CH(2))(5)[D-2Nal(2),Thr(4),Eda(9)]OVT, (6) d(CH(2))(5)[2Nal(2),Thr(4),Eda(9)]OVT, (7) d(CH(2))(5)[D-2Nal(2),Thr(4),Eda(9)<-- COCH(2)Ph(4-0H)(10)]OVT, (8) d(CH(2))(5)[2Nal(2),Thr(4),Eda(9)<-- COCH(2)Ph(4-OH)(10)]OVT. Peptides 1-8 were evaluated for agonistic and antagonistic activities in in vitro and in vivo rat bioassays, in rat OT receptor (rOTR) binding assays and in human OT receptor (hOTR) and human vasopressin (VP) vasopressor (V(1a)) receptor (hV(1a)R) binding assays. Also reported are the hOTR and hV(1a)R affinity data for atosiban and for B. None of the eight peptides exhibit oxytocic or vasopressor agonism. Peptides 1-8 exhibit weak antidiuretic agonism (activities in the range 0.014-0.21 U/mg). Peptides 1-6 exhibit potent in vitro (no Mg(2+)) OT antagonism (anti-OT pA(2) values range from 7.63 to 8.08). Peptides 7 and 8 are weaker OT antagonists. Peptides 1-6 are all OT antagonists in vivo (estimated in vivo anti-OT pA(2) values in the range 6.94-7.23). Peptides 1-8 exhibit vasopressor antagonism, anti-V(1a) pA(2) values in the range 5.1-7.65. Peptides 1-8 exhibit high affinities for the rOTR (K(i) values = 0.3-7.8 nM). Peptides 1-4 and B exhibit surprisingly very high affinities for the hOTR; their K(i) values are 0.17, 0.29, 0.07, 0.14 and 0.59 nM, respectively. Peptides 1-4 and B exhibit respectively 449, 263, 1091, 546 and 129 times greater affinity for the hOTR than atosiban (K(i) = 76.4 nM). Peptides 1-4 exhibit high affinities for the hV(1a)R (K(i)s = 1.1 nM, 1.3 nM, 0.19 nM and 0.54 nM, all higher than the hV1(a)R affinities exhibited by atosiban (K(i) = 5.1 nM) and by B (K(i) = 5.26 nM). Because of their strikingly higher affinities for the hOTR than atosiban, peptides 1-4 and B exhibit gains in anti hOT/anti hV(1a) receptor selectivity compared with atosiban of 93, 64, 39, 56 and 127, respectively. These OT antagonists are thus promising candidates for development as potential new tocolytic agents.

Animals↗
PubMed2006

Design and synthesis of potent, highly selective vasopressin hypotensive agonists.

We report here the solid-phase synthesis and vasodepressor potencies of a new lead vasopressin (VP) hypotensive peptide [1(beta-mercapto-beta,beta-pentamethylenepropionic acid)-2-0-ethyl-D-tyrosine, 3-arginine, 4-valine, 7-lysine, 9-ethylenediamine] lysine vasopressin, d(CH(2))(5)[D-Tyr(Et)(2), Arg(3), Val(4), Lys(7), Eda(9)]LVP (C) and 21 analogues of C with single modifications at positions 9 (1-13), 6 (14), 2 (16-20) and combined modifications at positions 6 and 10 (15) and 2 and 10 (21). Peptides 1-13 have the following replacements for the Eda residue at position 9 in C: (1) Gly-NH(2); (2) Gly-NH-CH(3); (3) Ala-NH(2); (4) Ala-NH-CH(3), (5) Val-NH(2); (6) Cha-NH(2); (7) Thr-NH(2); (8) Phe-NH(2); (9) Tyr-NH(2); (10) Orn-NH(2); (11) Lys-NH(2); (12) D-Lys-NH(2); (13) Arg-NH(2). Peptide 14 has the Cys residue at position 6 replaced by Pen. Peptide 15 is the retro-Tyr(10) analogue of peptide 14. Peptides 16-20 have the D-Tyr(Et) residue at position 2 in C replaced by the following substituents: D-Trp (16); D-2-Nal (17); D-Tyr(Bu(t))(18); D-Tyr(Pr(n)) (19); D-Tyr(Pr(i)) (20). Peptide 21 is the retro-Tyr(10) analogue of peptide 20. C and peptides 1-21 were evaluated for agonistic and antagonistic activities in in vivo vasopressor (V(1a)-receptor), antidiuretic (V(2)-receptor), and in in vitro (no Mg(2+)) oxytocic (OT-receptor) assays in the rat, and, like the original hypotensive peptide, d(CH(2))(5)[D-Tyr(Et)(2), Arg(3), Val(4)]AVP (A) (Manning et al., J. Peptide Science 1999, 5:472-490), were found to exhibit no or negligible activities in these assays. Vasodepressor potencies were determined in anesthetized male rats with baseline mean arterial blood pressure (BP) maintained at 100-120 mmHg. The effective dose (ED), in microg/100 g i.v., the dose required to produce a vasodepressor response of 5 cm(2) area under the vasodepressor response curve (AUC) during the 5-min period following the injection of the test peptide, was determined. The EDs measure the vasodepressor potencies of the hypotensive peptides C and 1-21 relative to that of A (ED = 4.66 microg/100 g) and to each other. The following ED values in microg/100 g were obtained for C and for peptides 1-21; C 0.53; (1) 2.41; (2) 1.13; (3) 1.62; (4) 0.80; (5) 1.83; (6) 1.56; (7) 2.12, (8) 2.58; (9) 1.40; (10) 0.88; (11) 0.90; (12) 0.85; (13) 0.68; (14) 0.99; (15) 1.05; (16) 0.66; (17) 0.54; (18) 0.33; (19) 0.18; (20) 0.15; (21) 0.14. All of the hypotensive peptides reported here are more potent than A. Peptides 20 and 21 exhibit a striking 30-fold enhancement in vasodepressor potencies relative to A. With a vasodepressor ED = 0.14, peptide 21 is the most potent VP vasodepressor agonist reported to date. Because it contains a retro-Tyr(10) residue, it is a promising new radioiodinatable ligand for the putative VP vasodilating receptor. Some of these new hypotensive peptides may be of value as research tools for studies on the complex cardiovascular actions of VP and may lead to the development of a new class of antihypertensive agents.

Amino Acid Sequence↗
PubMedDate not supplied

Altered uterine sensitivity to oxytocin and prostaglandin F2 alpha in dimethylbenz(a)anthracene (DMBA)-induced rat mammary carcinoma: the effects of tamoxifen and/or recombinant human interferon alpha 2b therapy.

This study aimed to investigate the long-term toxicity of a preventive regimen of tamoxifen (TAM) and recombinant human interferon alpha 2b (rHuIFN alpha 2b) on the uterine responsiveness of tumour-bearing rats. The experimental tumour was induced by dimethylbenz(a)anthracene (DMBA) in virgin female albino rats and the therapy was started two months after carcinogen administration. The acute effect of DMBA on the uterine sensitivity was also assessed 24 h post-carcinogen. The uterotonic potentials of oxytocin and prostaglandin F2 alpha (PGF2 alpha) were markedly reduced in the control tumour-bearing group as compared to the normal one. Similarly, acute DMBA administration showed reduced uterine sensitivity to both agents. Treatment with either TAM or combined TAM/rHuIFN alpha 2b did not affect the uterine response to either oxytocin or PGF2 alpha, while rHuIFN alpha 2b increased the uterine sensitivity to oxytocin but not to PGF2 alpha. These data indicate that the carcinogenic agent per se and the presence of tumour reduce the contractile response in the rat uterus to oxytocic agents. Moreover, combined TAM/rHuIFN alpha 2b does not markedly affect the uterine sensitivity in DMBA-induced mammary carcinoma-bearing rats.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1979

Defective N-oxidation of sparteine in man: a new pharmacogenetic defect.

Sparteine, an antiarrhythmic and oxytocic drug, is metabolised by N1-oxidation. The sparteine-N1-oxide rearranges with loss of water to 2- and 5-dehydrosparteine. 18 (i.e., 5%) out of 360 subjects were unable to metabolise the drug. These persons, who were designated as nonmetabolisers, excreted almost 100% of the administered dose in urine as unchanged drug. The defective metabolism of sparteine was found to have a genetic basis. Sparteine-N1-oxidation appears to be determined by two allelic genes at a single locus where nonmetabolisers are homozygous for an autosomal recessive gene.

Family↗
PubMed1987

Contragestion by antiprogestin RU 486: a review.

The steroidal derivative RU 486 (17 beta-hydroxy-11 beta-(4-dimethyl-aminophenyl 1)-17 alpha-(prop-1-ynyl)-estra-4,9-dien-3-one) is the first potent antiprogestin in medical use. Acting reversibly at the molecular level of receptor binding, RU 486 blocks progesterone action and allows endocrine functions to return quickly to normal after its use. However, target cells dynamics that depend upon a continuity of progesterone action will be irreversibly disrupted. In normal women RU 486 acts during the luteal phase in the endometrium, provoking bleeding, and also decreases LH secretion which results in luteolysis. In pregnant women, if affects the decidual, increases myometrial contractility and ripening of the cervix, and ultimately leads to termination of pregnancy. Detachment of the trophoblast leads to a fall in chronic gonadotrophin. Clinical studies indicate that RU 486 can be a very efficient agent for the termination of early pregnancy, and as a postcoital menstrual regulator. The failures observed when RU 486 is given alone may be overcome by the additional use of oxytocics. A small amount of prostaglandin given at the end of RU 486 treatment gives satisfactory results at up to 8 weeks of amenorrhea. Treatment with RU 486 is short term, and apparently has no significant side-effects despite the compound's antiglucocorticosteroid activity.

Abortifacient Agents↗