Biomedical subjects

Eszter Ducza

Publications and source records attributed to Eszter Ducza.

11 recordsLinked to original sources

PubMed2005

The ubiquitin-specific protease Usp4 regulates the cell surface level of the A2A receptor.

Many membrane proteins incur a folding problem during biosynthesis; only a fraction thereof is exported from the endoplasmic reticulum (ER), because quality control is stringent. This is also true for G protein-coupled receptors. Here, we identify the deubiquitinating enzyme Usp4 as an interaction partner of the A2a adenosine receptor, a Gs-coupled receptor. Usp4 binds to the carboxyl terminus of the A2A receptor and allows for its accumulation as deubiquinated protein. This relaxes ER quality control and enhances cell surface expression of functionally active receptor. The effect of Usp4 on the A2A receptor was specific because 1) it was not seen in C-terminally truncated versions of the receptor; 2) it was not mimicked by Usp14, another member of the ubiquitin-specific protease family; and 3) it was not seen with the metabotropic glutamate receptor-5, another G protein-coupled receptor with a high propensity for intracellular retention. These observations show that deubiquinating enzymes can regulate quality control in the ER.

Animals↗

PubMed2005

Correlation between the alterations in the mRNA expressions of the alpha1-adrenoceptor and estrogen receptor subtypes in the pregnant human uterus and cervix.

Our present aim was to determine the association between the mRNA expressions of the estrogen and adrenoceptor subtypes in the pregnant human uterus and cervix. The presence of the mRNA expressions of all the alpha1-adrenoceptor and estrogen receptor subtypes in the uterus and cervix was proved by means of a reverse transcription polymerase chain reaction method, with a predominance of the mRNAs of the alpha1B-adrenoceptor and estrogen alpha receptors, respectively. The change in the mRNA expression of the estrogen receptor alpha correlated strongly with the change in mRNA level of the alpha1B-adrenoceptors. We presume that the expression of the alpha1B-adrenoceptors at 33-34 weeks in the pregnant human uterus is regulated by estrogen through the estrogen receptor alpha subtypes.

Adult↗

PubMed2005

Terbutaline increases the cervical resistance of the pregnant rat in vitro.

Cervical ripening is a crucial process leading to delivery. Early dilation of the pregnant cervix can contribute to premature labour. The maturity of the cervix can be characterized by its resistance to mechanical stretching. Although a number of compounds are considered to increase cervical resistance (e.g., progesterone, nitric oxide synthase inhibitors and nonsteroidal anti-inflammatory drugs), none of them seem to be safe for clinical application. Other compounds, such as beta(2)-adrenergic receptor (beta(2)-AR) agonists, have been used for several decades to stop premature myometrium contractions, but their cervical action has never been investigated. The aim of this study was to detect the effects of the beta(2)-AR agonist terbutaline on nonpregnant and late-pregnant (day 18, 20, 21 or 22) cervices isolated from Sprague-Dawley rats. Cervical resistance was measured by means of a mechanical stretching test in vitro, the beta(2)-AR density was determined by Western blot analysis, the beta(2)-AR mRNA was determined by RT-PCR, while the G-protein activation following cervical beta(2)-AR stimulation with terbutaline was evaluated via a [(35)S]GTPgammaS binding assay. Terbutaline at 10(-6) M increased the cervical resistance of the late-pregnant samples in vitro from day 18 to day 22, but did not alter the resistance of the nonpregnant samples. This cervical resistance-increasing effect was concentration dependent and antagonized with propranolol on day 21. Terbutaline was ineffective on cervical samples when gradual stretching was omitted. RT-PCR and Western blot studies revealed increased beta(2)-AR mRNA and beta(2)-AR levels respectively on day 18 of pregnancy compared with the nonpregnant cervix, but no further changes were detected up to the end of pregnancy. The [(35)S]GTPgammaS binding assay demonstrated a decreased G-protein activation on the days of pregnancy investigated, but no activation was found in the nonpregnant samples. The degree of decrease in G-protein activation by terbutaline was in harmony with its cervical resistance-increasing action. On day 21, the G-protein activation-decreasing effect of terbutaline was antagonized with propranolol. We presume that the cervical resistance-increasing effect of terbutaline is a consequence of its G-protein activation-decreasing property via beta(2)-ARs, which finally leads to an increased muscle resistance against mechanical stretching. This action of terbutaline seems unique among the smooth muscles, and may open up a new perspective in the prevention of premature labour. Clinical experience indicates that beta(2)-AR agonists will not be sufficient to stop the overall process, but their combination with more potent inhibitors of uterine contractions may be of clinical benefit.

Adrenergic beta-Agonists↗

PubMed2005

Pregnancy-induced decrease in the relaxant effect of terbutaline in the late-pregnant rat myometrium: role of G-protein activation and progesterone.

The effectiveness of beta2-agonists in preterm delivery is reduced by several factors. The aim of this study was to determine the influence of late pregnancy in the uterus-relaxing effect of terbutaline in the rat in vitro. Rat uterine tissues from late pregnancy (days 15, 18, 20 and 22) were used. In vitro electrical field-stimulation (EFS) was used to evoke contractions. The radioligand-binding technique, reverse transcription-polymerase chain reaction and radioimmunoassay technique were used to determine the beta-adrenergic receptor density and mRNA level and the plasma sex hormone level, respectively. The activated G-protein level of the beta-adrenergic receptors was investigated by a radiolabelled GTP binding assay.EFS-induced contractions were inhibited by terbutaline. This effect decreased towards term with respect to both the EC50 and maximal inhibition values. A drop in plasma progesterone level was also detected. Binding studies revealed an increase in beta-adrenergic receptor number on the last day of pregnancy, which correlated with the change in receptor mRNA level. The G-protein-activating effect of terbutaline decreased continuously between days 15 and 20. Surprisingly, terbutaline decreased the G-protein activation to below the basal level on day 22. However, progesterone pretreatment set back the uterine action of terbutaline, increased the density of the beta2-adrenergic receptors and their mRNA level and increased the G-protein-activating property of terbutaline. These data provide evidence of a pregnancy-induced decrease in activated G-protein level after beta2-agonist stimulation. The decrease in plasma progesterone level has a crucial role in this process. The effects of beta2-adrenergic receptor agonists in tocolytic therapy may possibly be potentiated with progesterone.

Animals↗

PubMed2004

Investigation of estrogen receptor alpha and beta mRNA expression in the pregnant rat uterus.

Although the expressions of the estrogen receptor (ER) subtypes have been demonstrated in a large number of estrogen target tissues, to date no evidence has been reported as to how the expressions of the alpha (alpha) and beta (beta) ER subtype mRNA alter in the rat uterus during pregnancy. The aims of the present study were to obtain information concerning the changes in the ER and the progesterone receptor (PR) in early pregnancy and to determine the alterations in the ER subtype mRNA in the pregnant rat uterus. To demonstrate the ER and PR densities, radioligand saturation assay was used. The reverse-transcription-polymerase chain reaction (RT-PCR) was applied to characterize the alterations in the ER subtype mRNA. ER expression was highest on day 5 of pregnancy (Bmax = 637.40 +/- 76.10 fmol/mg). The PR expression did not change significantly until day 8, but the protein density was increased on day 8 of pregnancy. The ERalpha mRNA expression was active during pregnancy, maximum expression was attained on day 5; a gradual decrease was then observed until the second half of pregnancy when its expression continuously increased up to the day of labor (day 22). Since the attachment of the blastocyst, an event that is dependent on estradiol in the progesterone-primed uterus of the rat, occurs on day 5 of pregnancy and the levels of the ER protein and the ERalpha mRNA on day 5 of pregnancy was the highest, it could be supposed that this subtype of ER might regulate implantation. The ERbeta mRNA was detected only from day 7 to day 15, with a maximum level on day 8. The expression of this ER subtype might be related to the development of decidual tissue.

Animals↗

PubMed2004

Beta 2-agonist treatment enhances uterine oxytocin receptor mRNA expression in pregnant rats.

The objective of this study was to disclose an interaction between Beta(2)-adrenergic (Beta(2)-ARs) and oxytocin (OT) receptors (OTRs) in the late-pregnant rat uterus. We investigated the level of uterine OTR mRNA expression after the administration of Beta(2)-AR agonists fenoterol and hexoprenaline to rats from day 18 to 22 of pregnancy, and also tested the effect of fenoterol on uterine explants. Hexoprenaline induced a maximum 24% increase of OTR mRNA. Fenoterol in vivo elicited a maximum 125% increase of OTR mRNA, in vitro produced a maximum fourfold increase in OTR mRNA. In fenoterol-treated rats the maximal contractility increasing effect of OT on isolated uterine rings was significantly higher than in intact term pregnant rats, but the EC50 values were not statistically different. It was concluded that the enhanced expression of OTR mRNA induced by Beta(2)-agonists in the late-pregnant rat uterus may be a possible drawback to effective therapy of preterm uterine contractions with Beta(2)-agonists.

Adrenergic beta-Agonists↗

PubMed2003

Role of adrenergic receptor subtypes in the control of human placental blood vessels.

STATEMENTS OF THE PROBLEM: The use of beta2-Adrenergic Receptor (AR) agonists and the potential use of alpha1-AR blockers as tocolytics raise the question of how they influence placental circulation. The receptor profile was characterized via the amounts of the mRNA of alpha1-AR subtypes and beta2-ARs. The mRNAs were detected by reverse transcription-polymerase chain reaction. Electric field stimulation (EFS) was applied to test the pharmacological reactivity of the placental vessels. Expressions of beta2- and all subtypes of alpha1-AR mRNA were demonstrated in human placental vessels, and were significantly higher in the arteries. A significant difference was not found between the veins and the arteries as concerns the amount of alpha1D-AR mRNA. There was a preponderance of alpha1A- and alpha1B-AR mRNA as compared to alpha1D-AR mRNA both in the arteries and in the veins. beta2-AR agonists and alpha1-AR antagonists antagonized the EFS-induced contractions of the placental arteries in a dose-dependent manner. These effects were significantly less marked on veins at all applied doses. Urapidil antagonized the EFS-induced contractions of both the placental arterial and vein rings in a dose-dependent manner. The beta2-, alpha1A-, and alpha1B-AR are the important subtypes involved in the regulation of the contractility of the human term placental vessels. The possible increase in placental blood flow mediated by these ARs can even be beneficial during pregnancy. Accordingly, the use of beta2-AR agonists and the potential use of alpha1-blockers as tocolytics seem safe on the basis of in vitro examinations as concerns the placental circulation.

Adrenergic alpha-Antagonists↗

PubMed2003

Investigation of the role of the serotonergic activity of certain subtype-selective alpha1A antagonists in the relaxant effect on the pregnant rat uterus in vitro.

Results from recent studies have shown that alpha(1A)-adrenergic receptor (alpha(1A)-AR) antagonists could offer a new alternative in the treatment of preterm delivery. However, members of this group [2-(2,6-dimethoxyphenoxyethyl)aminomethyl-1,4-benzodioxane hydrochloride (WB4101), 5-methylurapidil (5-MU)] are known to influence serotonin (5-hydroxy-tryptamine) (5-HT(1A)) receptors, too. Our objective was to clarify the role of their 5-HT(1A) activities in the uterus relaxant effect. RT-PCR was used to determine mRNA expression of the receptor subtypes in 22 day pregnant rat uteri. Isolated uteri were stimulated by 5-HT or electrical field to investigate the contraction-inhibiting effect and the 5-HT(1A) activity of the alpha(1A) antagonists. Both receptor subtypes are present in rat myometrium. 5-HT induced contractions were inhibited by the alpha(1A) antagonists. Besides shifting the dose-response curve of 5-HT to the right, 5-MU decreased its maximal effect. The alpha(1A) antagonists inhibited electrical field stimulation-induced contractions. 5-HT(1A) blockade increased the maximal effect of 5-MU but did not change that of WB4101. These results suggest that the contraction increase caused by 5-HT is mediated by alpha(1A) receptors. Serotonergic activity of alpha(1) antagonists and especially alpha(1A) antagonists should be investigated as it may alter their efficacy and could interfere with their side-effects. It is proposed that novel alpha(1A) antagonists should be designed with no 5-HT(1A) activity to achieve maximal relaxant effect.

Adrenergic alpha-Antagonists↗

PubMed2002

Altered levels of mRNA expression and pharmacological reactivity of alpha1-adrenergic receptor subtypes in the late-pregnant rat myometrium.

The adrenergic system plays a major role in the regulation of the uterine contractility during pregnancy. Our previous studies have shown the significance of the alpha1-adrenergic receptors (ARs) in the control of pregnant uterine contractility both in vitro and in vivo. Our present aim was to determine the changes in mRNA expression and pharmacological reactivity of the alpha1-ARs on days 18, 20, and 22 of pregnancy. To demonstrate the expressions of alpha1-AR subtype mRNA, we used a reverse transcription-polymerase chain reaction (RT-PCR); the pharmacological reactivity was tested by electric field stimulation (EFS). The expression of alpha1A-AR mRNA increased from day 18 to 22, while no alpha1B-AR mRNA was detectable. We found a small increase in the expression of alpha1D-AR mRNA on day 20, which was not followed by a significant change in pharmacological reactivity. The alpha1D-receptor expression and pharmacological reactivity decreased significantly up to day 22. EFS studies revealed that the alpha1A-AR antagonist 5-methylurapidil had EC50 values (1.9 x 10(-6)-6.3 x 10(-6) M) about one order of magnitude lower than those of the alpha1D-AR antagonist BMY 7378 (4 x 10(-6)-3.6 x 10(-5) M). However, the alpha1B-AR antagonist cyclazosine exerted only a slight effect on the stimulated contractions. Strong correlations were found between the alpha1A-mRNA expression and the EC50 of 5-methylurapidil (r(2) =0.9712), and between the alpha1D-AR mRNA expression and the EC50 of BMY 7378 (r(2) = 0.9937). Our findings suggest that both alpha1A- and alpha1D-ARs are involved in the regulation of the pregnant uterine contractility. The density and pharmacological reactivity indicate that the alpha(1A)-AR seems to play the major role in late-pregnant myometrial contraction.

Animals↗

PubMed2002

In vitro and in vivo study in rats of rectal suppositories containing furosemide.

The aim of our experimental work was to formulate furosemide-containing rectal suppositories, to study drug release with in vitro membrane diffusion examinations and to increase drug liberation with the use of non-ionic surfactants (Solutol HS 15, Cremophor RH 60, Montanox 60 DF), which were incorporated in the suppository base in various concentrations. Suppocire AS2X proved to be the best suppository base (diffused drug: 69.78%). The use of 1% Cremophor RH 60 additive with the Witepsol H 15 base increased the quantity of the diffused drug from 62 to 75%. The membrane diffusion examinations were followed by studying the influence of suppository bases and additives exerted on the actual diuretic effect in Sprague-Dawley male rats. Once again the Suppocire AS2X suppository base gave the best results compared to the control; the quantity of the animals' urine showed a fourfold increase. Used with the Witepsol H 15 base, even 1% of all the three additives resulted in a considerable increase of diuretic effect, so their use proved to be advantageous. The comparison of the membrane diffusion examinations with the in vivo diuretic effect reveals that in vitro drug release and the pharmacological effect usually showed the same tendency, that is a greater extent of in vitro furosemide release was associated with a greater quantity of rat urine.

Administration, Rectal↗

PubMedDate not supplied

Effect of alpha-adrenoceptor subtype-selective inverse agonists on non-pregnant and late-pregnant cervical resistance in vitro in the rat.

1. The aim of the present study was to compare and elucidate the effects of alpha(1)-adrenoceptor (alpha(1)-AR) subtype-selective inverse agonists on non-pregnant and late-pregnant rat cervical tone. 2. Cervical resistance was investigated in in vitro stretching tests in the absence or presence of alpha(1)-AR subtype-selective inverse agonists (WB 4101, AH 11110A and BMY 7378; all at 10(-6) mol/L), whereas the mRNA levels and density of the alpha(1)-AR subtypes and the G-protein-activating effects of the inverse agonists were determined by reverse transcription-polymerase chain reaction, western blot and [(35)S]-GTPgammaS binding techniques, respectively. 3. The inverse agonists did not cause any change in resistance in non-pregnant and 18-day-pregnant samples. WB 4101 increased cervical resistance from Day 20, whereas AH 11110A had no effect and BMY 7378 exhibited such an action only on Day 21. Phenylephrine (10(-4) mol/L) had no effect on cervical resistance on Day 22. The mRNA levels and density of all alpha(1)-AR subtypes were increased on Day 18, but no further changes were observed after that. The [(35)S]-GTPgammaS binding studies revealed increased G-protein activation of alpha(1A)-AR and a moderate G-protein activation of alpha(1B)- and alpha(1D)-AR. The effect of WB 4101 to increase [(35)S]-GTPgammaS binding was blocked by pertussis toxin (50 ng/mL). Phenylephrine caused a slight and significant decrease in the amount of activated G-protein on Day 22. 4. The effects of inverse agonists on the alpha(1A)-AR can enhance cervical resistance in the late-pregnant rat in vitro. This action is mediated, at least in part, by a pertussis toxin-sensitive G(i)-protein. This effect of the alpha(1A)-AR inverse agonist WB 4101 may offer a new therapeutic target in the prevention of premature labour.

Adrenergic alpha-Agonists↗