Immunolocalization of retinol-binding protein, cellular retinoic acid-binding protein I and retinoid X receptor beta in the porcine reproductive tract during the oestrous cycle

Retinoid-binding proteins and nuclear receptors are expressed in the reproductive tissues of different species and their expression is hormonally regulated. In the present study, we demonstrated immunocytochemically the temporal and spatial localization of retinol-binding protein (RBP), cellular retinoic acid-binding protein I (CRABPI) and retinoid X receptor beta (RXRbeta) in porcine ovary, oviduct and uterus during the oestrous cycle. RBP and CRABPI were localized in the cytoplasm, whereas RXRbeta occurred in the nucleus. RBP was not detected in either the ovary or the oviduct at any stage of the oestrous cycle. CRABPI was present in luteal cells of the ovary only during dioestrus and in glandular and ciliated cells of the oviduct during oestrus. In the ovary, RXRbeta was always present in granulosa cells and germinal epithelium, with highest levels observed during oestrus. In the uterus, RXRbeta was present throughout the cycle in both the endometrium and the myometrium. However, changes in RXRbeta were observed in the endometrium, with highest levels observed during dioestrus. RBP and CRABPI could be observed in the endometrium only during dioestrus. The results show that the occurrence of retinoid-binding proteins and nuclear receptors in individual tissues of the reproductive tract are strongly dependent on the stage of the oestrous cycle. In the oviduct, the expression of CRABPI seems to be dependent on oestrogen, whereas in the uterus the expression of RBP and CRABPI is influenced by progesterone. The association of expression in different sections of the reproductive tissues investigated shows that the presence of specific proteins involved in retinoid metabolism was dependent on events associated with ovulation, the migration of the oocyte through the oviduct and the possible implantation of the blastocyst into the uterus.

Calcitonin immunostaining in monkey uterus during menstrual cycle and early pregnancy

Calcitonin has been shown to be a progesterone-regulated potential marker of the receptive endometrium in the rat and human. The present study was undertaken to immunohistochemically investigate the changes in calcitonin in the monkey uterus during the menstrual cycle and periimplantation period. Calcitonin immunostaining was primarily localized in the glandular epithelium on d 16, 20, and 25 of the menstrual cycle. During early pregnancy, calcitonin immunostaining was strongly observed in the glandular epithelium only on d 9 of pregnancy, the day before implantation. Since the high level of calcitonin immunostaining in the glandular epithelium during the luteal phase of the menstrual cycle and periimplantation period matched the high level of maternal progesterone during this period, the expression of calcitonin in monkey endometrium may be under the regulation of maternal progesterone.

Identification of urocortin mRNA and peptide in the human endometrium

Urocortin is a 40-amino acid peptide belonging to the corticotropin-releasing factor (CRF) family. In human reproductive tissues, urocortin expression has been previously demonstrated in the ovary, in the placenta and fetal membranes and in pregnant uterine tissues, while no data are available on the expression of the peptide in the nonpregnant uterus. In this study, urocortin expression was evaluated by both immunohistochemistry and reverse transcription-polymerase chain reaction, in human uterine tissues and cells at different phases of the menstrual cycle. Urocortin was immunolocalized in endometrial epithelial and stromal cells, as well as in the myometrium, and in vascular smooth muscle cells. No differences between proliferative and secretory phase were observed. These results were confirmed by reverse transcription-polymerase chain reaction analysis of isolated endometrial epithelial and stromal cells, and myometrial specimens. These findings open new questions on the roles played by urocortin in the human uterus.

Levels of estrogen and progesterone receptors in the myometrium and leiomyoma tissue after suppression of estrogens with gonadotropin releasing hormone analogs

Gonadotropin releasing hormone (GnRH) agonists are successfully used in the treatment of uterine leiomyomas. Different GnRH agonists may have different local effects on steroid receptors. This study was designed to evaluate potential differences in this respect between triptorelin (Decapeptyl) and goserelin (Zoladex) in a randomized controlled multicenter study using untreated patients during the luteal phase of their menstrual cycle as controls. Estrogen receptors (ERs) and progestin receptors (PRs) were measured by ligand binding assay in myoma and myometrium tissue following a 4-month treatment course with one of the GnRH analogs. In 18 untreated patients median values of ER and PR contents were comparable in myoma and myometrium: for ER at median levels of 56 and 43 fmol/mg protein, respectively; and for PR, median binding capacities were 690 and 730 fmol/mg protein, respectively. Both types of GnRH treatment (total number of patients 34) were associated with significant rises in ER in myoma (to a median level of 279 fmol/mg protein, p<0.001) and myometrium (to a median level of 109 fmol/mg protein, p<0.01). The increase in ER in myomas was significantly (p<0.001) greater than in myometria of the same patients (n=30). After treatment, PR in myomas (median level 520 fmol/mg protein) did not change significantly, but a significant (p<0.05) decrease was found for myometria (median level of 320 fmol/mg protein). Thus, ER and PR concentrations in myoma and myometrium are comparable before treatment, but estrogen suppression with GnRH analogs leads to a larger increase of ER level in leiomyomas than in myometrium, without an effect on PR, whereas myometria had lower PR levels. Therefore, leiomyoma reacts differently from myometrium towards lowered steroid concentrations in the circulation. Since the PR is considered to be a marker of estrogenic stimulation, this indicates remaining estrogenic effects on leiomyomas despite the large decrease of plasma estrogen concentrations.

[Cadmium concentration in uterine myomas, myometrium and peripheral blood from women living in Lower Silesia]

The author has studied the cadmium concentration in uterine myomas, myometrial tissue and peripheral blood in 72 women living in Lower Silesia. The highest cadmium concentration was observed in myometrial tissue, lower in uterine myomas and the lowest in the peripheral blood. The differences among the tissues were statistically significant. There were no significant differences in the cadmium concentration concerning the women's age. There was significant positive correlation in the cadmium concentration between the myomas and the myometrium.

Identification of the major proteoglycans from human myometrium

BACKGROUND

During pregnancy and parturition a remodeling within the extracellular matrix of the cervix and the corpus uteri occurs, which is of fundamental importance to a normal labor. The aim of this study is to identify the major proteoglycans in corpus uteri of non-pregnant subjects.

METHODS

From human uterine tissue proteoglycans were extracted and purified using CsCl-density gradient centrifugation, gel and ion-exchange chromatography. The proteoglycans were quantified and identified by Alcian Blue before and after ABC-digestion and by Western blotting.

RESULTS

The results showed that the corpus uteri contains a substantial amount of proteoglycans, 1.825 microg/mg wet weight. Decorin is dominating, constituting 63% of the total amount of proteoglycans. Heparan sulphate proteoglycans accounted for 20% and biglycan for 16%. Less than 1% consisted of the large proteoglycan versican.

CONCLUSIONS

Further investigations must be performed to provide more information of the biological role of the proteoglycans in the uterus, especially during labor, by the presence of heparan sulphate proteoglycans and the minute presence of versican which indicate that the proteoglycan composition and organization is different to that of the cervix.

Functional importance of bovine myometrial and vascular LH receptors and cervical FSH receptors

Bovine myometrium and cervix contain luteinizing hormone/human chorionic gonadotropin (LH/hCG) binding sites, LH receptor (LH-R) messenger RNA (mRNA), and LH-R protein. Expression of LH-R is dependent on the stage of the cycle. LH-R expression is high during the luteal phase but weak during the follicular phase. In both myometrium and cervix, LH activates both the adenylate cyclase and phospholipase C pathways, and the effect of LH on both pathways at each stage of the cycle is correlated with the amount of LH-R present in the tissue. Because activation of cyclic AMP (cAMP) is associated with myometrial quiescence, we suggest that LH activation of uterine cAMP could serve to keep the uterus quiescent during the luteal phase. On the other hand, in the uterine vein LH-R mRNA and LH-R are maximal during preestrus/estrus as opposed to the luteal phase. In the uterine vein, LH increases the expression of cyclooxygenase and production of both prostaglandin E2 (PGE2) and PGF2 alpha. Because PGF2 alpha is the physiological luteolytic signal in the cow, we suggest that this increase in prostaglandin production by the uterine vein is part of the physiological events leading to luteolysis. In addition to uterine LH-R, the bovine cervix at preestrus/estrus has high levels of follicle-stimulating hormone receptor (FSH-R) and its corresponding mRNA. As with LH-R, activation of FSH-R by FSH is associated with activation of a G protein-coupled receptor family that mediates the cAMP and inositol phosphate signaling pathways. Activation of these signaling pathways is associated with an increase in the expression of cyclooxygenase and production of PGE2. Because expression of the FSH receptor was maximal at the time of the FSH peak in the blood, we suggest a physiological role for FSH in the cervix relaxation and opening at estrus.

Expression and localization of the contractile prostaglandin F receptor in pregnant rat myometrium in late gestation, labor, and postpartum

A polyclonal antibody was raised against amino acids 7-18 in the first extracellular loop of rat prostaglandin F (FP) receptor to monitor expression and localization in pregnant rat myometrium at Gestational Days 16, 18, 20, 21, 21.5, 22 (delivery), and 23 (1-day postpartum; n = 5 per group). The antibody recognized a protein of approximately 43 kDa on Western blot analysis in both membrane (soluble and nonsoluble) and cytosolic fractions of myometrium on each day of gestation. Expression of FP protein increased significantly (P < 0.05) during late gestation in both soluble membrane and cytosolic fractions, being significantly greater at Day 21.5 than at Day 20 of gestation in the soluble membrane fraction and in the cytosolic fraction of tissues collected during labor compared with those obtained before labor. The total concentration of FP receptor in the membrane (soluble plus nonsoluble) remained high throughout late gestation and fell significantly (P < 0.05) in the postpartum period. The FP receptor in the soluble membrane fraction (compared to the total membrane FP receptor) was significantly (P < 0.05) higher in late gestation than earlier, whereas the ratio of FP protein in cytosolic to that in the total membrane was significantly (P < 0.05) higher on Day 23 than earlier in gestation, suggesting a dynamic movement of FP with advancing gestational age. Immunoreactive FP receptor localized to circular and longitudinal smooth muscle at all gestational ages, but changes in intracellular localization were observed in late gestation with a staining pattern similar to alpha-actin, suggesting an association with myofibrils. Our study suggests an increase in FP-receptor protein in myometrium with advancing gestation and a marked elevation at term. This supports a role for uterine FP receptors in mediation of uterine contractility at term.

Interactions between progesterone receptor isoforms in myometrial cells in human labour

Progesterone acts to maintain uterine quiescence during pregnancy. In contrast to many other species, no decrease in maternal serum levels of progesterone can be observed in humans before the onset of labour. Therefore, a 'functional' progesterone withdrawal in association with labour has been proposed. In humans the progesterone receptor (PR) exists in two isoforms, PR-A and PR-B. While PR-B generally mediates the effects of progesterone upon gene transcription, the role of PR-A during pregnancy, and in parturition, is unknown. In this study, term myometrium cells cultured before the onset of labour were transiently transfected with expression vectors for either PR-A or PR-B. Only those cells expressing PR-B significantly increased expression of a progesterone-sensitive reporter when stimulated with progesterone. Co-transfection of both isoforms of PR demonstrated that PR-A is a dominant repressor of transactivation in these cells. Western blot analysis showed that PR-A is present in human myometrium samples taken only after, but not before, the onset of labour. These data suggest that increased expression of PR-A in human myometrium may contribute to 'functional' progesterone withdrawal and the initiation of human labour.

Oxytocin and lysophosphatidic acid induce stress fiber formation in human myometrial cells via a pathway involving Rho-kinase

The actin cytoskeleton is important for stress fiber formation and contributes to the initiation and maintenance of smooth muscle contraction. To determine if oxytocin and lysophosphatidic acid (LPA) induce stress fiber formation, cultured human myometrial cells were exposed to oxytocin (10(-5) M) or LPA (10(-6) M), and filamentous (F) and globular (G) actin pools were stained with fluorescein isothiocyanate-phalloidin and Texas red DNase I, respectively. The F- to G-actin fluorescent-staining ratio was measured by fluorescence microscopy. Oxytocin and LPA increased stress fiber formation, as indicated by an increase in the F- to G-actin fluorescent-staining ratio. The Rho-kinase inhibitor Y-27632 markedly attenuated this increase. Oxytocin-induced stress fiber formation was completely inhibited in the presence of the oxytocin antagonist compound VI. Tyrosine kinase inhibition with tyrphostin A23 partially blocked the increase induced by oxytocin but had no effect on LPA-induced stress fiber formation. Stress fiber formation was not blocked by pertussis toxin, mitogen-activated protein kinase, or protein kinase C inhibitors. Our results show that human myometrial cells respond to oxytocin and LPA with the formation of stress fibers that may be involved in the maintenance of uterine contractions. Rho-kinase appears to be a key signaling factor in this pathway.

Identification of oligomeric domains within dermatan sulfate chains using differential enzymic treatments, derivatization with 2-aminoacridone and capillary electrophoresis

Galactosaminoglycans, i.e. dermatan sulfate (DS) and chondroitin sulfate, are linear heteropolysaccharides consisting of repeating disaccharide units of L-iduronic acid (L-IdoA) or D-glucuronic acid (D-GlcA) residues linked to N-acetyl-galactosamine. High-performance capillary electrophoresis (HPCE or CE) has been successfully used for determining the disaccharide composition of glycosaminoglycans. However, only limited information is available on how to identify oligomeric domains rich in D-GlcA or L-IdoA. The aim of this study was therefore to develop a rapid and accurate CE procedure by which such oligosaccharides can be determined together with the variously sulfated disaccharides. Isolated dermatan sulfates of human origin were separately digested with chondroitinases ABC, AC and B and the enzymic products were derivatized with 2-aminoacridone. CE analysis of these products was performed using a phosphate buffer, pH 3.0, and reversed polarity at 30 kV. The derivatization enabled their detection with laser-induced fluorescence (LIF) and UV at 260 nm at much higher sensitivity than the detection of nonderivatized delta-saccharides at 232 nm and therefore components undetectable at 232 nm were nicely detected after derivatization. Except for delta-disaccharides, altogether five distinct oligosaccharides with differences in charge density were identified. Depending on the lyase that produced these oligomers, information on the presence of L-IdoA- or D-GlcA-containing domains within the DS chain and the sulfation pattern of these oligomeric domains was obtained. This CE method could also be useful in studying the functional oligomeric domains in galactosaminoglycan chains.

Activin betaA-subunit and activin receptors in human myometrium at term and during labour

OBJECTIVE

To measure activin A content and to localise and semi-quantitate activin receptors in human myometrium at term and during labour.

DESIGN

Myometrium was collected from non-pregnant women (n = 6), pregnant women at term not in labour (n = 6) and at term in labour (n = 6).

SETTING

Monash Medical Centre, Melbourne, Australia.

MAIN OUTCOME MEASURES

Tissue lysates of myometrium were analysed for activin A content using an enzyme-linked immunosorbent assay and activin receptor proteins IA, IIA and IIB using Western hybridisation. Activin betaA-subunit and activin receptors were localised in myometrium by immunohistochemistry.

RESULTS

Activin A was detected by ELISA in non-pregnant, pregnant and labouring myometrium. Levels were significantly higher in labouring myometrium. The three activin receptors IA, IIA and IIB were detected in all myometrial samples by Western hybridisation. Receptor IA was expressed in significantly higher levels in pregnant myometrium. Receptor IIA was very weakly expressed throughout. The expression of receptor IIB was similar in all three groups. Activin betaA-subunit and all three receptors were localised to the endothelial cells of myometrial blood vessels. Neither activin betaA-subunit nor any of the three activin receptors were immunolocalised to myometrial smooth muscle cells in the three groups. This result was confirmed by Western blotting for expression of activin receptors in isolated myometrial smooth muscle and microvascular endothelial cells.

CONCLUSION

The myometrium is not a target for activin A during late pregnancy or labour. However, activin A may have a role in the regulation of microvascular endothelial cell function in the myometrium.

Temporospatial Changes of Kinin B2 Receptors During the Estrous Cycle and Pregnancy in the Rat Uterus1

Tissue kallikreins are present in rat uterus during the estrous cycle in luminal and glandular epithelium, in early gestation in the implantation node, and in the last third of pregnancy surrounding the sinusoids in the decidua basalis. The pattern of kinin B2 receptor expression, through which the vasoactive effect of kallikreins is exerted, was studied by in vitro autoradiography and immunohistochemistry. The kinin B2 receptor was observed in the luminal and glandular epithelium, myometrium, endothelial cells of arteries, veins and venules, and smooth muscle cells of endometrial and myometrial arterioles. Immunoblotting of crude membranes revealed a band of 69 kDa that increased in late proestrus and estrus, concordantly with the pattern of immunostaining observed in the tissue. At Day 7 of gestation, the kinin B2 receptor was expressed (binding sites and receptor protein) in the epithelium of the implantation node and decidual cells; these latter cells showed a further increase during gestational Days 9 and 10. From Days 14 to 21, the subplacental decidua became strongly immunoreactive, and on Days 16 and 21 the placental labyrinthine endothelium was intensely stained. During this period, endothelium of arteries and veins, smooth muscular cells of small diameter arterioles, and myometrium also expressed B2 receptors. In unilaterally oil-stimulated pseudopregnancy, the decidual cells and the glandular epithelium show similar immunoreactivity to that during pregnancy. The temporospatial pattern of kinin B2 receptors, coinciding with that of kallikrein or with sites accessible to the generated kinins, further supports an autocrine-paracrine role for the kallikrein-kinin system in the vasoactive changes of implantation and placental blood flow regulation.

Identification, quantification and fine structural characterization of glycosaminoglycans from uterine leiomyoma and normal myometrium

The type, amount and fine chemical composition of glycosaminoglycans (GAGs) present both in human normal myometrium and uterine leiomyoma have been studied. GAGs were fractionated by ion-exchange chromatography on DEAE-Sephacel, isolated by gel-permeation chromatography on Sepharose CL-6B and characterized using electrophoresis in cellulose acetate membranes, specific enzymic treatments and analysis by high-performance capillary electrophoresis (HPCE). No statistical intrabatch differences in total GAG content in both tissues were identified, whereas significant interbatch differences between normal myometrium and uterine leiomyoma were recorded. Hyaluronan (HA), chondroitin sulphate (CS), dermatan sulphate (DS), heparan sulphate (HS) and keratan sulphate (KS) were identified in both tissues. Statistically significant (P </= 0.001) differences in uterine leiomyoma in the content of HA (-27.7%), DS (+158.5%), KS (+116.4%) and HS (-52.5%), as compared to normal myometrium, were determined. Despite the differences in the amount of GAGs, no significant differences in the fine chemical composition of CS and DS were identified. It is worth noting that DS of both tissues is constructed by glucuronic acid-containing long repeats separated by a few iduronic acid residues. The results of this study suggest that the development of uterine leiomyoma is closely related to quantitative changes at the GAG level. The increase of DS and KS may well be related to increased neosynthesis of fibrotic connective tissue, whereas the decrease of HA and the unaltered amounts of CS may also indicate benign tumors of low growth rate.

Expression of basic fibroblast growth factor (bFGF), FGF receptor 1 and FGF receptor 2 in uterine leiomyomas and myometrium during the menstrual cycle, after menopause and GnRHa treatment

BACKGROUND

To investigate whether basic fibroblast growth factor (bFGF) is involved in the growth regulation of human uterine leiomyomas the expression of bFGF and its receptors was measured in leiomyomas and myometrium obtained under different endocrine conditions.

METHODS

The expression of bFGF, fibroblast growth factor receptor 1 (FGFR1) and fibroblast growth factor receptor 2 (FGFR2) was analyzed by immunohistochemistry and Western blot.

RESULTS

Twenty-seven women with leiomyomas included eight in the proliferative phase, seven in the secretory phase, six after menopause and six after GnRHa treatment. In the proliferative phase, bFGF staining in leiomyomas was significantly stronger than in any other leiomyoma group. After GnRHa treatment, the expression of bFGF in both leiomyomas and myometrium was weaker than in the proliferative phase. The staining of FGFR1 was less intense in proliferative phase myometrium than in myometrium from any other group, significantly weaker than in the secretory phase. The leiomyomas demonstrated homogeneous cytoplasmic FGFR1 staining that was similar in all groups, except in the GnRHa treated patients where a more intense staining was observed, significantly stronger than in proliferative phase leiomyomas. No tissue differences were observed for staining of FGFR2 and no significant differences were observed between the different groups. Slightly less staining of FGFR2 was found in leiomyomas in the secretory phase but it did not reach statistical significance. The specificity of immunostaining was confirmed by Western blot.

CONCLUSIONS

We suggest that the regulation of bFGF, and to some extent also its receptors in leiomyomas and in myometrium, is influenced by sex steroid hormones. However, the lack of differences in expression between leiomyomas and myometrium favors the view that bFGF does not necessarily contribute to the differences in growth regulation in these tissues.

Galactosaminoglycans from normal myometrium and leiomyoma

In many tumors, the amount of chondroitin sulfate in the extracellular matrix has been shown to be elevated when compared to the corresponding normal tissue. Nevertheless, the degree of chondroitin sulfate increase varies widely. In order to investigate a possible correlation between the amount of chondroitin sulfate and tumor size, several individual specimens of human leiomyoma, a benign uterine tumor, were analyzed. The glycosaminoglycans from eight tumors were extracted and compared with those from the respective adjacent normal myometrium. The main glycosaminoglycan found in normal myometrium was dermatan sulfate, with small amounts of chondroitin sulfate and heparan sulfate. In leiomyoma, both dermatan sulfate and chondroitin sulfate were detected and the total amounts of the two galactosaminoglycans was increased in all tumors when compared to normal tissue. In contrast, the heparan sulfate concentration decreased in the tumor. To assess the disaccharide composition of galactosaminoglycans, these compounds were incubated with bacterial chondroitinases AC and ABC. The amounts of L-iduronic acid-containing disaccharides remained constant, whereas the concentration of D-glucuronic acid-containing disaccharides increased from 2 to 10 times in the tumor, indicating that D-glucuronic acid-containing disaccharides are responsible for the elevation in galactosaminoglycan concentration. This increase is positively correlated with tumor size.

Effects of gestational age and labor on expression of prostanoid receptor genes in baboon uterus

We determined the effect of gestational age and labor on the regional expression of prostanoid receptor genes in baboon myometrium. Cesarean hysterectomy was performed on 15 pregnant baboons of known gestational age in the last third of pregnancy, five of them during spontaneous term labor. Expression of prostanoid receptor genes was studied using Northern blot analysis. Transcripts of similar size to the human were detected for prostanoid EP(1), EP(2), EP(3), EP(4), IP, FP, and TP receptor genes using Northern blot analysis. There were no gestational age-related changes in expression of these genes. Expression of EP(1), EP(3), and IP receptor RNA mRNA was significantly higher in myometrium from the fundus (compared with the lower segment), whereas EP(2) gene expression was significantly lower in the fundus. Labor was associated with a reduction in the regional variation of both EP(2) and IP receptor gene expression, but not EP(1) and EP(3) expression. Labor was also associated with an overall lower level of expression of EP(2) receptor mRNA. We conclude that regional and labor-related variation in myometrial expression of prostanoid receptor genes may have a key role in primate parturition.

Interleukin 8 production and interleukin 8 receptor expression in human myometrium and leiomyoma

OBJECTIVE

Interleukin 8 is a potent chemoattractant cytokine that is expressed in a variety of human tumors and is known to induce mitogenesis. We aimed to investigate the production of interleukin 8 and the expression of its receptor in myometrium and leiomyoma, in which we hypothesized that interleukin 8 may contribute to cellular proliferation.

STUDY DESIGN

Myometrial and leiomyoma tissue pairs (n = 14) were obtained from human uteri after hysterectomy conducted for leiomyomatous uterus. Expression of interleukin 8 and interleukin 8 receptor type A was identified in the leiomyomatous myometrium by means of specific antibodies directed against interleukin 8 and interleukin 8 receptor type A for immunohistochemical detection. Interleukin 8 production by cultured cells was measured by enzyme-linked immunosorbent assay. The regulation of interleukin 8 messenger ribonucleic acid expression was assessed by means of the Northern blot analysis after treatment of myometrial cells with interleukin 1alpha and tumor necrosis factor alpha. Myometrial cell proliferation was determined by means of colorimetric assay after cells were treated with interleukin 8 and antihuman interleukin 8 neutralizing antibody.

RESULTS

Immunostaining for both interleukin 8 and interleukin 8 receptor type A was stronger in the myometrium adjacent to leiomyoma compared with leiomyoma itself (2-fold, P <.05). Compared with samples from nonusers, samples from patients who had used gonadotropin-releasing hormone agonists revealed a trend for decreased staining for both interleukin 8 and interleukin 8 receptor type A. Interleukin 1alpha and tumor necrosis factor alpha caused a time- and dose-dependent increase in interleukin 8 production by myometrial cells (P <.001). There was a dose-dependent inhibition of cell proliferation with antihuman interleukin 8 antibody to 55% of the control (P <.001).

CONCLUSION

Our demonstration of high levels of interleukin 8 and its receptor in myometrium immediately surrounding leiomyoma and the inhibition of cell proliferation when interleukin 8 is blocked by a neutralizing antibody suggest a potential role for interleukin 8 in the growth of myometrial tissue surrounding leiomyomatous tissue. This study could lead to a better understanding of potential involvement of cytokines in leiomyoma growth and in gonadatropin-releasing hormone agonist-induced regression.

Regulation of progesterone receptors and decidualization in uterine stroma of the estrogen receptor-alpha knockout mouse

Regulation of progesterone receptor (PR) in uterine stroma (endometrial stroma plus myometrium) by estrogen was investigated in estrogen receptor-alpha (ERalpha) knockout (alphaERKO) mice. 17 beta-Estradiol (E(2)) increased PR levels in uterine stroma of ovariectomized alphaERKO mice, and ICI 182 780 (ICI) inhibited this E(2)-induced PR expression. Estrogen receptor-beta(ER beta) was detected in both uterine epithelium and stroma of wild-type and alphaERKO mice by immunohistochemistry. In organ cultures of alphaERKO uterus, both E(2) and diethylstilbestrol induced stromal PR, and ICI inhibited this induction. These findings suggest that estrogen induces stromal PR via ERbeta in alphaERKO uterus. However, this process is not mediated exclusively by ERbeta+, because in ERbeta knockout mice, which express ERalpha, PR was up-regulated by E(2) in uterine stroma. In both wild-type and alphaERKO mice, progesterone and mechanical traumatization were essential and sufficient to induce decidual cells, even though E(2) and ERalpha were also required for increase in uterine weight. Progesterone receptor was strongly expressed in decidual cells in alphaERKO mice, and ICI did not inhibit decidualization or PR expression. This study suggests that up-regulation of PR in endometrial stroma is mediated through at least three mechanisms: 1) classical estrogen signaling through ERalpha, 2) estrogen signaling through ERbeta, and 3) as a result of mechanical stimulation plus progesterone, which induces stromal cells to differentiate into decidual cells. Each of these pathways can function independently of the others.

BK(Ca) channel activation by membrane-associated cGMP kinase may contribute to uterine quiescence in pregnancy

We investigated the influence of pregnancy on large-conductance calcium-activated potassium channel (BK(Ca)) activity (NP(o)) and on channel expression in membranes of isolated human myometrial smooth muscle cells. NP(o) in inside-out patches was higher in pregnant myometria (PM) compared with nonpregnant myometria (NPM), and the half-maximal activation potential was shifted by 39 mV to more negative potentials. This effect was not due to an enhanced BK(Ca) channel expression. In the presence of cAMP kinase (PKA) or cGMP kinase (PKG), NP(o) increased in patches from PM but decreased in those from NPM. Western blot analysis and use of a specific PKG inhibitor (1 microM KT-5823) verified the existence of a partially active membrane-associated PKG. Inhibition of PKA by 100 nM PKI, the inhibitory peptide of PKA, had no effect on NP(o). 8-p-Chlorophenylthio-cGMP (8-pCPT-cGMP) hyperpolarized cells from PM. This effect was abolished by iberiotoxin, a specific blocker of BK(Ca) channels. It is concluded that an endogenous, membrane-bound PKG in myometrial cells specifically enhances BK(Ca) channel activity during pregnancy and thus may contribute to uterine quiescence during pregnancy.

Localization and characterization of urocortin during human pregnancy

Urocortin, a recently identified peptide of the corticotropin releasing hormone (CRH) peptide family, has potent vasodilatory effects in the human fetal placental circulation in vitro, promoting us to hypothesize that urocortin is produced locally to regulate uteroplacental vascular tone during pregnancy. In the present study, we examined the distribution of urocortin in the human placenta, fetal membranes and uterine tissue at term in the presence and absence of labour, using a urocortin antibody produced in our laboratory and the immunoperoxidase staining method. Immunoreactive (IR)-urocortin was observed in the vascular smooth muscle of the myometrium (n=5), decidual stromal cells, syncytiotrophoblast and amnion epithelium (n=10). No differences in staining intensity for urocortin were detected between tissues obtained in the absence (n=5) or presence (n=5) of labour. Staining intensity for IR-urocortin was greatest in the decidua suggesting this may be a site of urocortin production during pregnancy. Subsequently, we tested urocortin secretion from chorio-decidual cells in vitro, using an immunoblot technique. Positive staining for urocortin was observed in 40 per cent of chorio-decidual cells with 34 per cent of these cells secreting urocortin under basal conditions. Since urocortin was secreted by decidual cells we questioned whether urocortin was present in maternal plasma throughout gestation, using radioimmunoassay. Urocortin was detectable in maternal plasma from 7 weeks of gestation and concentrations did not change as gestation progressed. IR-urocortin in the maternal plasma eluted from a Sephadex G-50 column at the same site as synthetic urocortin and had a calculated retention coefficient (Kd) of 0.44. In summary, this study indicates that urocortin is produced by the decidua during human pregnancy and is detectable in maternal plasma. These data are consistent with the hypothesis that urocortin is produced locally by the decidua and may act to regulate uteroplacental blood flow.

Altered gene expression of endothelin-A and endothelin-B receptors, but not endothelin-1, in myometrium and placenta from pregnancies complicated by preeclampsia

OBJECTIVE

The aim of the present study was to compare the mRNA expression of endothelin-1 (ET-1), ET-1 receptors ET(A) and ET(B) in myometrium and placenta obtained from biopsies collected from women with preeclampsia (n=10) or normal pregnant (n=12).

METHODS

The mRNA levels of ET-1 ET(A) and ET(B) were determined using RT-PCR and expressed as arbitrary units after correction for control GAPDH gene mRNA levels.

RESULTS

The mRNA levels of ET-1 in myometrium and placenta were not altered in women with preeclampsia compared to normal pregnant. The mRNA expression of ET(A) was significantly reduced (p<0.05) in both placenta and myometrium from women with preeclampsia. The mRNA levels of ET(B) were similar in placentas from both preeclamptic and normal pregnant women, but higher in myometrium (p<0.05) from women with preeclampsia.

CONCLUSIONS

These results indicate that the higher levels of ET-1 seen in preeclamptic women do not depend on an altered mRNA transcription of ET-1. The significantly reduced mRNA expression of ET(A) receptor in myometrium and placenta in women with preeclampsia might represent downregulation of the receptors due to the increased levels of ET-1 in uteroplacental circulation in this disorder. Much more research is needed before the role of ET(B) receptors in preeclampsia can be clarified.

Oxytocin modulates the onset of murine parturition by competing ovarian and uterine effects

Recent analysis of mice deficient in both oxytocin (OT) and cyclooxygenase-1 has shown that OT exerts significant effects on both the ovarian corpus luteum and the uterine myometrium during pregnancy. To better define the roles of OT during pregnancy, we evaluated OT action and OT receptor regulation in wild-type and OT-deficient knockout (KO) mice. Continuous infusion of OT revealed that OT can either delay labor at low doses or initiate preterm labor at high doses. The infusion rates of OT necessary for these effects were reduced in OT KO mice. The dose of OT that delayed labor also delayed the normal decrease in plasma progesterone late in gestation, implicating a primary effect on the corpus luteum. Consistent with this hypothesis, luteal OT receptor expression exceeded that of the myometrium until luteolysis occurred. We propose that the downregulation of OT receptors in the corpus luteum and induction of OT receptors in the myometrium serve to shift the predominant consequence of OT action during murine pregnancy from labor inhibition to labor promotion.

Low myometrial glycogen content compared with rectus muscle in term pregnant women before labor

Glycogen, glucose, some nucleosides and purine base derivatives were determined in biopsies from 10 term pregnant women undergoing elective cesarean sections before labor. The concentrations were compared in the biopsies which were cut from isthmus and fundus of the uterus and m. rectus abdominis. M. rectus biopsies had 1.5 and 2 times higher concentration of glycogen than the isthmic and fundal uterine biopsies, respectively. The glucose concentration in the striated muscle was on the other hand only half that in the myometrium. The uterus displayed regional differences in concentrations of glycogen (higher in isthmus). A relatively low glycogen content in term pregnant uterine smooth muscle compared with striated muscle signifies the restricted energy demands of pregnant myometrium.

Proton NMR spectroscopy of the phospholipids in human uterine smooth muscle and placenta

The parameters regulating the fluidity of myometrial and placental phospholipids include double bonds, fatty acid chain lenght and the cholesterol/phospholipid ratio. The transformation of these parameters was studied during pregnancy and labor. Myometrial and placental tissue samples were collected from 24 patients: 6 were nonpregnant, 6 early-pregnant, 6 late-pregnant not in labor and 6 in labor. After butanol extraction, tissue cholesterol and lipid phosphorus were determined. Proton NMR spectroscopy of the phospholipids was performed at 500 MHz. The myometrial cholesterol/phospholipid ratio was slightly elevated in pregnant patients not in labor. The uterine muscle of the nonpregnant patients contained more CH=CH groups in the phospholipids than that of the late-pregnant patients. There were 29 more double bonds in placental than in uterine tissue per 100 fatty acid molecules. The average fatty acid chain length varied from 14.0 to 18.8. The placenta has longer fatty acid chains than the uterine smooth muscle. The myometrial carbon chain was shortened on the average by 1.4 and the placental by 1.0 carbon atoms, when the patient went into clinical labor. These findings suggest fluidity changes in myometrial and placental phospholipids during human pregnancy and labor.