The effect of the release of exogenous nitric oxide on the responses of the pregnant human myometrium to oxytocin.

Objective: Introduction: Currently there is insufficient evidence to support the routine administration of nitric oxide donors in the treatment of threatened preterm labor. An understanding of the role that nitric oxide plays in the management of threatened preterm labor may lead to more effective treatment and prevention. The aim of our study was to examine the involvement of exogenous nitric oxide release in regulating responses of the human pregnant myometrium to oxytocin.

The sources of calcium for noradrenaline-induced contraction in the human thoracic internal artery.

The aim of the present study was to examine the contribution of intracellular and extracellular calcium sources in contraction caused by noradrenaline (NA) of the human internal thoracic artery (ITA) in vitro. Distal segments of ITA were obtained from 20 patients (aged 38-73, at the time of routine coronary artery surgical revascularization (CABG)). Contractile responses to 10 mol/L NA in the physiological salt solution and in Ca-free solution without and after incubation with 10 mol/L thapsigargin (TSG) were recorded under isometric conditions.

Altered uterine contractility in response to β-adrenoceptor agonists in ovarian cancer.

We aimed to prospectively examine β-adrenoceptor-mediated uterine contractility in women suffering from gynecological malignancies. Myometrial specimens were obtained from non-pregnant women undergoing hysterectomy for benign gynecological disorders, and ovarian, endometrial, synchronous ovarian-endometrial, and cervical cancer. Contractions of myometrial strips in an organ bath before and after cumulative dosages of β- and β-adrenoceptor agonists with preincubation of propranolol, SR 59230A, and butoxamine were studied.

Cu(II) complexation does not affect oxytocin action on pregnant human myometrium in vitro.

Objective: Copper may influence the in vivo and in vitro uterine activity. Recent evidence shows that cupric ions can easily form complexes with oligopeptides like oxytocin (OXT). The high complex stability in vitro suggests a possibility of complex formation in vivo.

Differences in the effects of beta2- and beta3-adrenoceptor agonists on spontaneous contractions of human nonpregnant myometrium.

Objective: This study aimed to compare the relaxant properties of BRL 37344 with p2-adrenoceptors agonist ritodrine on the contractility of human nonpregnant myometrium.

Material And Methods: The activity of myometrial strips mounted in an organ bath was recorded under isometric conditions using force transducers with digital output. Contractility before and after cumulative additions of both uterorelaxants and with preincubation with beta-adrenoceptor antagonists bupranolol, propranolol, and butoxamine were studied.

Influence of potent and selective beta-adrenoceptor agonist, CL 316243, on the contractile response of non-pregnant human myometrium.

Unlabelled: The purpose of this study was to evaluate the effect of beta(3)-adrenoreceptor agonist, CL 316243 on human non-pregnant uterine contractility. The activity of myometrium strips was recorded by means of force transducers with digital output. Quantification of the response of myometrium strips was done by calculation of the area under the curve (AUC), as well as the amplitude and frequency of contractions.

Effect of nitric oxide on responses of the human uterine arteries to vasopressin.

Nitric oxide (NO) is known to be an important relaxant of contractile activity in various muscles including the human uterine arteries. It has been suggested that NO plays a role in modulation of vascular action of arginin vasopressin (AVP), a strong vasoconstrictor of the human uterine arteries. Therefore, the purposes of this study were to investigate an involvement of endogenous NO in regulation of responses of the human intrauterine arteries to AVP and examine the effect of exogenous NO on contractions of the human intrauterine arteries evoked by AVP.

The influence of methylene blue on the spontaneous contractity of the non-pregnant human myometrium and on the myometrial response to DEA/NO.

Nitric oxide (NO) is a potent inhibitor of spontaneous contractions of the human non-pregnant myometrium; however, the precise mechanism by which NO causes the myometrial smooth muscles to relax remains unclear. The aim of this study was to determine the influence of methylene blue (MB) on myometrial contractions and the response of the myometrium to DEA/NO in vitro. Concentration-response curves to DEA/NO were constructed in the absence and presence of MB (5x10(-6), 10(-4) and 10(-2) mol/l) and 5x10(-3) mol/l cystamine.

[Cadmium level in the human saphenous vein used in coronary artery bypass grafting].

The human saphenous vein is the main superficial vein of the lower limb. It begins on the foot, runs across among medial surface of shin and knee and frontal-medial surface of thigh. Saphenous vein remains the most widely used bypass conduit for the treatment of occlusive coronary and peripheral vascular disease.

Influence of low molecular weight heparin preparations on human internal thoracic artery contraction.

Objective: Low molecular weight heparins (LMWHs) offer practical and potential pharmacological advantages over unfractionated heparin in multiple applications but have not been studied as vasoactive agents. The purpose of this study was to investigate the effects of two commercial preparations of LMWHs, enoxaparin sodium and nadroparin calcium, on vasoconstriction in the human internal thoracic artery (ITA) in vitro.

Methods: Samples of redundant ITA segments obtained from 36 patients who underwent coronary artery bypass surgery were cut into 3mm wide rings and suspended in 20 ml organ bath.

Cu(II) complexation potentiates arginine vasopressin action on nonpregnant human myometrium in vitro.

Copper may influence in vivo and in vitro uterine activity. Recent evidence has shown that cupric ions can easily form complexes with oligopeptides like arginine vasopressin (AVP). The high complex stability in vitro suggests a possibility of complex formation in vivo, in the uterus of intrauterine device users.

The effect of a selective inhibition of potassium channels on the relaxation induced by nitric oxide in the human pregnant myometrium.

The aim of this study was to investigate whether apamin-sensitive K(+)channels play a role in the NO induced relaxation of the human pregnant myometrium. Concentration-response curves for sodium nitroprusside (SNP) (10(-9)-10(-4)M) were constructed in the absence and presence of 10(-8)M apamin and 10(-7)M charybdotoxin (CTX). Preincubation with apamin resulted in a significant attenuation of the relaxation caused by SNP, while pre-treatment with CTX insignificantly decreased the SNP induced relaxation.

Apamin inhibits NO-induced relaxation of the spontaneous contractile activity of the myometrium from non-pregnant women.

There is now considerable evidence for the involvement of K+ channels in nitric oxide (NO) induced relaxation of smooth muscles including the myometrium. In order to assess whether apamin-sensitive K+ channels play a role in NO - induced relaxation of the human uterus, we have studied the effect of specific blockers of these channels on the relaxation of myometrium from non-pregnant women. In vitro isometric contractions were recorded in uterine tissues from non-pregnant premenopausal women who had undergone hysterectomy.

Source of calcium for contractile responses of large and small human intramyometrial arteries.

The role of calcium (Ca(2+)) released from intracellular stores and the entry of extracellular Ca(2+) for vasopressin (AVP)-induced responses in large and small, human, intramyometrial arteries was investigated. There was no statistical difference as revealed by pD(2) values (-log EC(50)), in the sensitivity of large and small vessels to AVP. Nimodipine caused an inhibition of contractions induced by low concentrations (10(-10) mol/l) of AVP in both types of vessels but, at higher concentration (>10(-10) mol/l), whereas responses in small arteries were diminished, in large arteries they remained unchanged.

Receptor binding of oxytocin and vasopressin antagonists and inhibitory effects on isolated myometrium from preterm and term pregnant women.

Objective: To test binding affinities for, and inhibitory effects on, myometrium of some oxytocin and vasopressin antagonists with respect to their therapeutic potential.

Design: Receptor binding studies on transfected cell lines. In vitro contractility studies of human myometrium.

Involvement of K+ATP channels in nitric oxide-induced inhibition of spontaneous contractile activity of the nonpregnant human myometrium.

Nitric oxide (NO), an important endogenous substance, is known to be a strong relaxant of smooth muscle, including myometrium. It has been postulated that the relaxing effect of NO on smooth muscle is achieved by the stimulation of soluble guanylyl cyclase, which leads to an increase in the cyclic guanosine 3',5'-monophosphate (cGMP) levels and hyperpolarization of the cellular membrane. The aim of our study was to investigate the involvement of K+ATP channels in the mechanism of cGMP-independent nitric oxide-induced inhibition of contractile activity of the nonpregnant human myometrium, obtained at hysterectomy.

[The effects of heparin on intrauterine arteries of the human non-pregnant uterus: II. The analysis of the route of action].

Objective: Our purpose was to elucidate the mechanism of heparin action on smooth muscle of small intramyometrial arteries.

Material And Method: Material was obtained, contractility and calcium concentration were measured as previously described. Calcium influx to the vascular cells was also measured.

[The effects of heparin on intrauterine arteries of the human non-pregnant uterus: I. The action of clinically administered heparin].

Objective: Our purpose was to study the action of commercial unfractionated heparin on small human myometrial arteries, in vitro.

Material And Method: Pieces of myometrial arteries, about 1 mm. in external diameter, were obtained from premenopausal women undergoing hysterectomy.

Effects of the vasopressin V1a receptor antagonist, SR 49059, on the response of human uterine arteries to vasopressin and other vasoactive substances.

Background: Arginine vasopressin (AVP) activates the uterus via V1a receptors and is apparently an important factor for the myometrial hyperactivity, uterine ischemia and pain of primary dysmenorrhea. The orally active and selective, non-peptide AVP1a receptor antagonist, SR 49059, has been shown to inhibit the myometrial action of AVP, but the specific influence of this substance on the effects of AVP and other vasoactive agents on human uterine arteries is unknown.

Methods: Concentration-responses of AVP on isolated medium-sized human uterine arteries were studied after incubation with only vehicle (DMSO, 0.

Potent inhibition by tamoxifen of spontaneous and agonist-induced contractions of the human myometrium and intramyometrial arteries.

Objective: Our purpose was to elucidate the mechanism of direct (nongenomic) action of antiestrogens on spontaneous and agonist-induced contractions of the human myometrium and uterine arteries.

Study Design: Myometrial strips and pieces of uterine arteries were obtained from nonpregnant premenopausal women undergoing hysterectomy. Spontaneous activity of myometrium and responses of myometrium and artery to K(+)-depolarization and vasopressin were recorded under isometric conditions.

Inhibition of contractile responses of human myometrium and intramyometrial arteries by potassium channel openers.

Objectives: The effects of cromakalim and pinacidil on the contractile activity of the isolated human myometrium and intramyometrial arteries were studied.

Material And Method: Myometrial strips and pieces of uterine arteries were obtained from women undergoing hysterectomy. Contractions were recorded under isometric conditions.

Effects of cadmium on myometrial activity of the nonpregnant human. Interactions with calcium and oxytocin.

With respect to recent reports suggesting an involvement of cadmium in preterm labor, the effects of this ion on the activity of myometrial strips from term pregnant women were examined. The interactions of cadmium with calcium and oxytocin on myometrial activity were also studied. Cadmium alone inhibited spontaneous contractile activity already in a concentration of 10(-9) M and in 10(-3) M myometrial contractions were almost completely abolished.

Effect of ovarian steroids and diethylstilbestrol on the contractile responses of the human myometrium and intramyometrial arteries.

Estriol, estradiol, progesterone and diethylstilbestrol in the concentration range of 0.2-40 microM inhibited the spontaneous contractions of the myometrium in a dose-dependent manner but the differences in IC50 values obtained with different hormones were not statistically significant. All these hormones caused a concentration-dependent inhibition of the K(+)-induced contraction.

Influence of cadmium ions on the reactivity of isolated human uterine arteries.

The isometric contractions were recorded for pieces of uterine arteries as well as ascending branches of uterine artery (1-2 mm diameter) obtained from 36 nonpregnant, premenopausal women undergoing hysterectomy. Contractile responses to K(+)-depolarization, noradrenaline, and Ca+2 ions were studied. Cadmium at concentrations 10(-9)-10(-3) M produced no changes of tension in the investigated arteries.