左旋18-甲基炔诺酮和米非司酮对分泌中期人子宫内膜HOXA11基因表达的影响

目的:通过口服孕激素类(左旋18-甲基炔诺酮,Levenorgestrel,LNG)和抗孕激素类(米非司酮,RU486)避孕药,研究孕激素对分泌中期人子宫内膜HOXA11基因表达的影响。方法:30名自愿者,于正常月经周期排卵后d7,刮取内膜组织做自身对照;实验周期在排卵前或排卵后2d,口服小剂量LNG(18例)或RU486(12例),同样在排卵后d7刮取内膜组织。用原位杂交方法检测服药子宫内膜HOXA11基因表达的变化。结果:对照组(分泌中期)内膜,间质细胞普遍表达HOXA11mRNA,而腺上皮HOXA11的表达则呈弱阳性或阴性。口服LNG后,子宫内膜形态变化不明显;内膜腺上皮HOXA11表达量进一步下降或无明显变化(即用药前后均表达阴性);间质细胞HOXA11表达增强。服用RU486后,内膜发育明显延迟,腺上皮HOXA11表达强度普遍大于对照组,而间质细胞的表达变化无明显规律。结论:孕激素对内膜腺上皮HOXA11基因的表达起负调控作用;正常分泌中期,内膜腺上皮HOXA11表达减弱或消失是内膜分化成熟的标志。     

Alterations in expression of endometrial endothelial nitric oxide synthase and alpha(v)beta(3) integrin in women with endometriosis

OBJECTIVE: To determine the expression of endometrial endothelial nitric oxide synthase (eNOS) protein and alpha(v)beta(3) integrin in patients with and without endometriosis. DESIGN: Case-control cohort study. SETTING: University-based tertiary care center. PATIENT(S): Endometrial biopsy samples were obtained from 9 fertile women with regular cycles and 30 infertile women with varying severity of endometriosis. Peritoneal fluid levels of nitric oxide were determined in 13 infertile women with a normal pelvis and 12 infertile women with endometriosis. MAIN OUTCOME MEASURE(S): Expression of eNOS and alpha(v)beta(3) integrin protein in the endometrium and peritoneal fluid levels of nitric oxide. RESULTS: In patients with endometriosis, expression of eNOS was significantly increased in the glandular and luminal epithelium, with no significant changes in the stroma. Peritoneal fluid levels of nitric oxide were unchanged, and expression of alpha(v)beta(3) integrin expression in glandular and luminal epithelium was significantly decreased compared with controls. A significant negative correlation was observed between luminal expression of eNOS and alpha(v)beta(3) integrin and between glandular expression of eNOS and luminal expression of alpha(v)beta(3) integrin. CONCLUSION(S): The nitric oxide pathway may play a role in the pathogenesis of endometriosis.     

Nitric oxide induces endometrial secretion at implantation time

BACKGROUND. Uterine cervical secretory cells receive a sympathetic cholinergic secretomotor innervation. Glandular nitric oxide (NO) production has been proposed to be a prerequisite for muscarine-induced carbohydrate secretion from endometrial glands and cervical glands at ovulation time and from the seminal vesicle glands. Nitric oxide has also been suggested to have a significant role in the process of implantation and early pregnancy in the mouse, a process, which has also been compared with an inflammatory response. METHODS. The carbohydrate secretion from everted guinea pig uterine horns placed in organ baths was estimated. Polymerase chain reaction was performed in order to identify the isoforms of nitric oxide synthase (NOS). results. Carbamylcholine chloride (Carbachol) induced carbohydrate secretion of the endometrium, whereas L-NNA and L-NAME inhibited the Carbachol-induced secretion. The isomer D-NAME had no effect on Carbachol-induced secretion. The NO donor GTN induced carbohydrate secretion of the endometrium. The addition of the nitrergic inhibitor of soluble guanylyl cyclase (sGC) ODQ to Carbachol and to the NO donor GTN gave a reduced response. No synergism was seen when the sGC stimulator YC-1 was applied together with Carbachol. Three isoforms of NOS - endothelial NOS (eNOS), cytokine-inducible NOS (iNOS), and neuronal (nNOS) - were identified at implantation time and may take place in the endometrial cell. CONCLUSIONS. The results of this study suggest that glandular NO production is a prerequisite for the autonomic nervous modulation of endometrial secretion in the guinea pig and that NO may play a role in the implantation time.     

Normal human endometrium. An ultrastructural survey

An ultrastructural review of the cyclic changes of endometrial surface and glandular epithelial cells, stromal cells and the stromal microvasculature is presented. Endometrial biopsies were collected from infertile patients with endometriosis or tubal dysfunction. During the proliferative phase, the ergastoplasm and Golgi apparatus of surface and glandular epithelial cells become well-developed, while increasing numbers of mitochondria are seen. In the early secretory phase, the postovulatory triad composed of glycogen accumulation, nuclear channel system and giant mitochondria is described and its functional significance is discussed. Premenstrual cellular involution due to enhanced lysosomal activity such as apoptosis and lysosomal wrapping is detailed. Before ovulation, the endometrial stromal cells are primarily involved in the secretion and remodelling of the extracellular connective tissue fibers and ground substance. After predecidual change, the stromal cells exhibit marked macropinocytotic and phagocytotic properties. We suggest that these proteolytic activities of the stromal cells, together with the presence of blood-derived phagocytes, may account for endometrial clearance, since there are no lymphatic channels in the superficial endometrium. According to this hypothesis, tissue fluid may be drained via the fenestrated (venous) endometrial blood capillaries.     

Expression of matrix metalloproteinase-26 and tissue inhibitor of matrix metalloproteinase-3 and -4 in endometrium throughout the normal menstrual cycle and alteration in users of levonorgestrel implants who experience irregular uterine bleeding

OBJECTIVE: To determine the expression of matrix metalloproteinase (MMP-26) and tissue inhibitor of MMP (TIMP) in the endometrium of women with normal menstrual cycles compared with users of levonorgestrel implants. DESIGN: Prospective observational study. SETTING: Academic research center. PATIENT(S): Fifty patients with normal menstrual cycles who requested permanent surgical sterilization (tubal ligation) and 35 users of levonorgestrel implants. INTERVENTION(S): Endometrial biopsy. MAIN OUTCOME MEASURE(S): Expression of MMP-26, TIMP-3, and TIMP-4 by immunohistochemistry and semiquantitative analysis of staining intensity by using the H score. RESULT(S): Endometrium from women with a normal menstrual cycle and users of levonorgestrel implants expresses MMP-26, TIMP-3, and TIMP-4. These substances are present in various types of endometrial cells; expression is strongest in surface and glandular epithelial cells, followed by vascular endothelial and endometrial stromal cells. Inflammatory and immune-related cells also stained strongly for MMP-26 and TIMPs. Semiquantitative analysis of the staining intensity of endometrial epithelial and stromal cells indicated that expression of MMP-26, TIMP-3, and TIMP-4 peaks during the early to mid-luteal phase. Expression of MMP-26 is elevated in users of levonorgestrel implants who experienced irregular uterine bleeding. CONCLUSION(S): Endometrial expression of MMP-26 and TIMP-4 is present throughout the menstrual cycle and is elevated during the early to mid-luteal phase in normally cycling women. Further elevations in MMP-26 are seen in users of levonorgestrel implants who experience irregular uterine bleeding. These substances thus seem to play a role in hormonal regulation and endometrial tissue remodeling.     

Lectin binding of endometrium in women with unexplained infertility

OBJECTIVE: To investigate whether peri-implantation phase endometrium in women with unexplained infertility differs from the endometrium of normal fertile women. DESIGN: Assessment of the function of the endometrium by using endometrial biopsy specimens and lectin histochemistry. SETTING: Infertility Clinic, Jessop Hospital for Women, Sheffield, United Kingdom. PATIENTS: Eighteen normal fertile women (group I) and 18 women with unexplained infertility (group II). INTERVENTIONS: Endometrial biopsies were obtained from both groups at 5, 7, and 9 days after the luteinizing hormone (LH) surge. MAIN OUTCOME MEASURES: Five biotinylated lectins, concanavalin A (ConA), wheat germ agglutinin (WGA), soybean agglutinin, Peanut, and Ulex europaeus I were used as analytical probes to study endometrial glycoconjugates. Histochemical staining was performed using the avidin-biotin peroxidase method. The lectin binding by endometrial glands, surface epithelium, stromal cells, and vessels was assessed. RESULTS: In group I, ConA stained the subnuclear glandular cytoplasm, glandular lumen, stroma cells, and surface epithelium. In group II, ConA binding to glandular or surface epithelium was none or equivocal. In group I, WGA bound to glandular cytoplasm and stroma cells on days LH + 5 and LH + 7. In group II, WGA binding was absent in glands but present in stroma. CONCLUSIONS: Reproductive failure of women with unexplained infertility may be associated with defective biosynthesis and distribution of glycoconjugates that subsequently results in an unfavorable endometrial environment during the peri-implantation phase.     

Endometriosis and free radicals

Recent studies have shown that synthase for nitric oxide or scavenger enzymes is distributed throughout the endometrium. We have reported that endothelial nitric oxide synthase, originally identified in vascular endothelial cells, is distributed in glandular epithelial cells in the endometrium, peaking in the midsecretory phase. In addition, it is known that superoxide dismutase is distributed throughout the endometrium, varying with the menstrual cycle. Yet it is not clear how these enzymes are committed in the reproductive processes. Endometriosis is often complicated by infertility and miscarriage. Of particular interest is that these enzymes are overexpressed in the disease throughout the menstrual cycle. These findings strongly suggest that excessive amounts of free radicals are produced in endometriosis. Copyrightz1999S.KargerAG,Basel     

Endometrial glandular dysplasia and endometrial intraepithelial neoplasia

PURPOSE OF REVIEW: In recent decades, progress has been made in defining endometrial precancers. Endometrial intraepithelial neoplasia has been widely accepted as a precancer of type I endometrial cancer, while endometrial glandular dysplasia is a newly described entity as a probable precancer of type II cancer. As endometrial intraepithelial neoplasia has been discussed more extensively in the literature, we focus more on the recent development of endometrial glandular dysplasia in this review. RECENT FINDINGS: Serous endometrial intraepithelial carcinoma was previously considered as a putative precancer for endometrial serous carcinoma or uterine papillary serous carcinoma. It is now considered as an early form of endometrial serous carcinoma, however. Endometrial glandular dysplasia was found to be a better candidate for precancer for both endometrial serous and clear cell carcinomas, which meets almost all recently defined criteria for precancer. Biomarkers of p53 and IMP3 are helpful for the early detection of endometrial glandular dysplasia as well as type II endometrial cancers. SUMMARY: Two types of endometrial cancers are derived from two different precancers. Type I endometrioid carcinoma develops from endometrial intraepithelial neoplasia, while type II derives most probably from endometrial glandular dysplasia. Recognition and correct detection of endometrial glandular dysplasia may deepen our understanding and improve prevention and clinical management for type II endometrial cancer.     

Nitric oxide increases endocervical secretion at the ovulatory phase in the female

BACKGROUND: Uterine cervical mucus is crucial for reproduction, facilitating sperm transport and survival in certain mammals. Cholinergic autonomic nervous secretory innervation has been established, and modulation of secretion by prostaglandins and non-steroidal anti-inflammatory drugs has been postulated. It has been suggested that glandular nitric oxide (NO) production is a prerequisite for the autonomic cholinergic nervous modulation of cervical, endometrial, and the seminal vesicle secretion in the guinea pig. Most secretory genital tract cells, female as well as male, seem to display NO synthase activity. METHODS: Cervical secretion at ovulation time was studied in 10 women with regular menstruation. In an in vivo model with repeated collection of mucus samples during four 60-min periods, the amount of mucus was estimated in a control experimental series and in an experimental series following sublingual administration of the NO donor nitroglycerin. RESULTS: This nitroglycerin administration markedly increased cervical secretion, while no changes in cervical secretion were seen in the control experimental series. CONCLUSIONS: The results suggest that glandular NO production increases cervical secretion. Thus, cervical secretion may, apart from hormonal regulation, be influenced by the autonomic nervous system, and in addition, NO may be a prerequisite for this influence. This in turn may have implications on fertilization and fertility regulation.     

子宫内膜腺上皮及基质细胞分离、培养作为子宫内膜异位症体外细胞模型的探索

目的 :探索在位子宫内膜腺上皮及基质细胞的分离、培养作为子宫内膜异位症 (EMs)的体外细胞模型。方法 :通过酶解、系列过滤、沉降及贴壁纯化等技术 ,分离、纯化及培养 15份EMs患者的在位子宫内膜腺上皮细胞及其基质细胞 ,并拟传代。结果 :11份标本获得成功 ;每 1g新鲜子宫内膜组织可得到 (8～ 12 )× 10 6个原代基质细胞及 (4～ 8)× 10 6个原代腺上皮细胞 ;基质细胞纯度率可达 95 %以上 ,腺上皮细胞的纯度率约为90 %。基质细胞可以有限的传代 ,腺上皮细胞不能传代。通过改良步骤 ,可提高基质细胞的产量。结论 :在位子宫内膜腺上皮及其基质细胞的分离、培养可作为EMs的体外细胞模型之一。     

Activin-A secretion is increased in the eutopic endometrium from women with endometriosis

BACKGROUND: Activin is a well-characterised growth and differentiation factor and an important inflammatory mediator. Activin is secreted by normal endometrial glands and stroma and is expressed by endometrial leucocytes. It is also known that the eutopic endometrium from women with endometriosis is functionally different to that from women without endometriosis. In this study, we hypothesise that the endometrial secretion of activin is altered in women with endometriosis. AIMS: To determine whether the expression of inhibin/activin subunits and the secretion of activin-A is different in eutopic endometrium from women with and without endometriosis. METHODS: Endometrial biopsies were obtained from premenopausal, regularly menstruating women with and without endometriosis. Staining intensity for the different inhibin/activin subunits was compared in endometrial and endometriotic biopsies. Activin-A secretion was studied using endometrial explants and endometrial glandular and stromal monolayer cell cultures. RESULTS: The alpha- and betaA-subunits of inhibin/activin were more abundant in eutopic glandular cells from patients with minimal to mild endometriosis compared to women without endometriosis. In patients with endometriosis, the betaB-subunit was more abundant in eutopic stromal cells and endometrial leucocytes. Comparison of paired endometrial and endometriotic biopsies from the same patient did not reveal significant differences for any of the inhibin/activin subunits or activin receptors. Activin-A secretion by glandular and stromal endometrial cells was sevenfold and threefold higher, respectively, in women with endometriosis compared to women without endometriosis. CONCLUSIONS: The expression of inhibin/activin subunits in eutopic endometrium is altered in women with endometriosis, leading to higher levels of activin-A secretion by both glandular cells and stromal cells.     

The expression and functionality of transient receptor potential vanilloid 1 in ovarian endometriomas

Pains of various kinds-dysmenorrhea, chronic pelvic pain, and dyspareunia-are the major complaints from women with endometriosis, representing the most debilitating nature of the disease. Despite extensive research, our understanding as how endometriosis causes pain is still fragmentary. In this study, we examined transient receptor potential vanilloid 1 (TRPV1)-positive nerve fibers in ectopic endometrium from women with ovarian endometriomas and in endometrium from women without endometriosis and correlated the density with the severity of dysmenorrhea in cases. We also performed an immunohistochemistry analysis of TRPV1 in ectopic and control endometrium. After finding TRPV1 immunoreactivity in ectopic endometrial cells, we further examined whether TRPV1 is functional in ectopic endometrial stromal cells (EESCs). We found that the density of TRPV1-positive nerve fibers in ectopic endometrial implants is higher than that in control endometrium and correlates positively with the severity of dysmenorrhea in women with endometriosis. In addition, TRPV1 expression was also found to be elevated significantly in EESCs when stimulated with inflammatory mediators such as prostaglandin E2 (PGE(2) ) and tumor necrosis factor-α (TNF-α). Finally, we found that TRPV1 activation can induce the release of nitric oxide (NO) and interleukin 1β (IL-1β) in EESCs. The latter finding appears to be consistent with the reports of increased TRPV1 protein expression following peripheral inflammation. Our results suggest that the increased TRPV1-positive nerve fibers may integrate various stimuli on peripheral terminals or primary sensory neurons and generate hyperalgesia in endometriosis. The expression and functionality of TRPV1 in EESCs also suggest that TRPV1 may have neurosecretory functions that are yet to be elucidated.     

人子宫内膜细胞的体外纯化和培养

目的:旨在建立一套子宫内膜细胞体外培养和贮存传代的方法。方法:用胶原酶消化和铜网过筛法分离子宫内膜基质细胞和上皮细胞,进行单层培养。结果:子宫内膜腺上皮细胞和基质细胞分别经角蛋白单抗和波形蛋白单抗组化染色为阳性,腺上皮细胞可持续培养4-6周,传代2-3次;基质细胞可持续培养5-8周,传代4-6次。结论:建立了可体外培养贮存、传代的子宫内膜细胞,为进一步对其进行抗原组分研究奠定基础。     

改良筛网法分离培养人子宫内膜细胞

目的:探索一种能获得较高纯度和较多数量子宫内膜细胞的分离培养方法。方法:取12例患者各1mg新鲜子宫内膜组织,经0.25%Ⅰ型胶原酶(含有0.005%DNA酶)消化后,将所得细胞悬液一分为二,分别采用传统筛网法和改良筛网法(二次筛网过滤和低速离心相结合)分离并记录所得细胞数;体外培养后采用光学显微镜观察,用免疫细胞化学和免疫荧光化学方法鉴定纯度,比较两种方法分离子宫内膜细胞的纯度和数量。结果:两种方法均有11例组织分离培养成功。传统筛网法分离的子宫内膜腺上皮细胞和间质细胞的纯度分别为(89.54±3.75)%和(92.82±1.60)%,细胞数分别为(0.47±0.09)×105个和(23.73±5.37)×105个。改良筛网法分离的腺上皮细胞和间质细胞纯度分别为(91.95±0.47)%和(99.28±0.21)%,细胞数分别为(8.09±1.24)×105个和(27.23±0.50)×105个。改良筛网法分离的腺上皮细胞数量和间质细胞纯度均明显高于传统筛网法,有统计学差异(P均=0.000)。结论:改良筛网法操作简单,能获得较高纯度的子宫内膜间质细胞及较多的子宫内膜腺上皮细胞。     

HOXA11基因在人良、恶性子宫内膜增生组织中的表达及临床意义

目的:探讨HOXA11蛋白在人子宫内膜良、恶性增生组织中的表达及临床意义。方法:采用免疫组化方法检测正常增生期(20例)、单纯型及复杂型增生(39例)、不典型增生(33例)和子宫内膜腺癌(41例)子宫内膜组织中HOXA-11的蛋白表达情况。结果:HOXA11在人子宫的内膜腺上皮和间质、肌层及血管壁中均有表达,其中在内膜腺上皮和间质的表达随着增生程度的增加而呈下降趋势,子宫内膜癌组织则显著性下降(P<0.01),在肌层及血管壁中表达各组间无差异。结论:在子宫内膜由良性到恶性增生的演变过程中,HOXA11表达呈下降趋势,可作为子宫内膜恶性变的生物学指标之一。     

Effects of peritoneal macrophages from women with endometriosis on endometrial cellular proliferation in an in vitro coculture model.

OBJECTIVE: To study the effects of peritoneal macrophages on endometrial cellular proliferation in an in vitro coculture model and to compare the magnitude of these effects between macrophages from women with endometriosis and normal women. DESIGN: Controlled study of peritoneal macrophage function. SETTING: University hospital. PATIENT(S): Patients with a normal peritoneal cavity (n = 15) and with pelvic endometriosis (n = 20) undergoing laparoscopy. INTERVENTION(S): Peritoneal macrophages were cocultured with endometrial epithelial and stromal cells; endometrial cell cultures without macrophage coculture acted as controls. MAIN OUTCOME MEASURE(S): Endometrial cellular proliferation measured by 3H-thymidine incorporation. RESULT(S): Endometrial epithelial cells cocultured with peritoneal macrophages from women with endometriosis showed significantly increased proliferation compared with cocultures using macrophages from normal women when assessed at 24 hours (1.56 versus 1.03 times, respectively, over control) and at 72 hours (1.55 versus 1.10 times over control). Endometrial stromal cells cocultured with peritoneal macrophages from women with endometriosis similarly exhibited increased proliferation compared with cocultures using macrophages from normal women when assessed at 24 hours (1.65 versus 1.17 times over control) and at 72 hours (1.65 versus 1.21 times over control). CONCLUSION(S): Peritoneal macrophages of patients with endometriosis stimulate cellular proliferation of endometrial epithelial and stromal cells in vitro.     

Is endometrial apoptosis evidence of endometrial aging in unexplained infertility? a preliminary report

OBJECTIVE: To investigate spontaneous endometrial apoptosis in women with unexplained infertility and to find out whether there is a possible relationship between endometrial apoptosis, age, and hormonal parameters. STUDY DESIGN: This study was designed as a prospective, case-controlled study in a University Hospital setting. A total of 34 endometrial biopsies were performed from 17 women with unexplained infertility and 17 fertile controls, who were admitted for tubal ligation. Endometrium was sampled on the seventh post-ovulatory day. On the same day of endometrial sampling, serum levels of FSH, LH, PRL, TSH, E2, progesterone, 17alpha-hydroxyprogesterone, testosterone and DHEA-S were determined. Endometrial glandular and stromal apoptosis were investigated by DNA nick end labeling (TUNEL) method on each sample. Endometrial apoptotic index was calculated and correlated with age and hormonal parameters. RESULTS: There was no difference in either endometrial glandular apoptotic index (AI) or stromal AI between the groups. However, the mean glandular AI was significantly higher than the mean stromal AI (p = 0.0001). There was a strong correlation between endometrial AI and age (r = 0.91, p = 0.02). Serum T levels were significantly found to be decreased in the unexplained infertility group (p = 0.0001). In addition, serum TSH levels were positively correlated with AI in the glandular endometrium in women with unexplained infertility (r = 0.611, p = 0.009). CONCLUSION: Endometrial apoptosis increases with age. Serum levels of testosterone were lower in unexplained infertility. The effect of serum TSH levels on apoptosis in the glandular epithelium of the endometrium needs further studies.     

Differential in vitro actions of nitric oxide on human endometrial cell survival

Objective

To investigate the presence of caspase-3 and Bcl-2 concentration in human endometrial tissue throughout the menstrual cycle, and study the effect of nitric oxide (NO) on cell proliferation and apoptosis during culture.

Design

Expression of caspase-3 and Bcl-2 concentration in endometrial explants, and examination of L-arginine (L-Arg) effect on epithelial and stromal cell proliferation and apoptosis in vitro.

Setting

Prospective study.

Patient(s)

Twenty-seven eumenorrheic women (37 ± 1.2 years).

Intervention(s)

Endometrial samples were obtained with Pipelle suction curette from the corpus of the uterus.

Main outcome measure(s)

Apoptosis (annexin V-FITC binding), Bcl-2 concentration (ELISA), caspase-3 (immunohistochemistry), cell proliferation (spectrophotometric assay), and gene expression (RT-PCR).

Result(s)

Caspase-3 was detected by immunoassay in epithelial tissue throughout the menstrual cycle and in stroma during secretory phase. The Bcl-2 concentration was similar in endometrial homogenates obtained throughout the menstrual cycle, but L-Arg decreased Bcl-2 only in endometrium from the proliferative phase. In epithelial cells, NO increased apoptosis by 2.1 ± 0.2-fold, augmented mRNA expression of Bax, and reduced expression of Bcl-2 compared with basal cultures. In stromal cells, NO increased cell proliferation in a dose-dependent manner, an effect that was blocked by a NO synthase inhibitor.

Conclusion(s)

These data indicate that NO has a differential regulatory function on endometrial cell survival, as indicated by the results on stromal cell proliferation and epithelial cell apoptosis during culture, which suggests paracrine interactions between both cell types.     

Localized increase in nitric oxide production and the expression of nitric oxide synthase isoforms in rat uterus with experimental intrauterine infection.

OBJECTIVE: We recently reported that nitric oxide was associated with increased mortality among pregnant rats with intrauterine infection. In our current study we investigated the expression of different isoforms of nitric oxide synthases and nitric oxide in the nonpregnant rat uterus with experimental intrauterine infection. STUDY DESIGN: Pathogenic Escherichia coli was inoculated into the uterine lumen of ovariectomized rats. Animals were killed after inoculation, and uterine horns were collected for assessing nitric oxide production with high-performance liquid chromatography and nitric oxide synthase (type II and type III) protein expression with Western immunoblotting and immunofluorescence methods. RESULTS: (1) Nitric oxide production increased in the infected uterine horn in a time-dependent manner after intrauterine infection but did not increase in the uninfected horn. (2) Nitric oxide synthase type III protein contents did not show a difference between infected and uninfected horns, and type III nitric oxide synthase was expressed by the epithelial cells and smooth muscle cells. (3) Type II nitric oxide synthase was abundantly expressed in infected horns but was not expressed in uninfected horns. Immunofluorescence data indicated that macrophages and natural killer cells, located in the endometrial layer clustering around epithelial cells, expressed type II protein. CONCLUSION: We suggest that localized increase in type II nitric oxide synthase expression and nitric oxide production occurs in response to intrauterine infection and that the nitric oxide system may play a role in host response to restrict the infection.