Ovarian nitric oxide synthase (NOS) gene expression during peripubertal development

Cell-specific expression and immunolocalization of nitric oxide synthase isoforms and the related nitric oxide/cyclic GMP signaling pathway in the ovaries of neonatal and immature rats

OBJECTIVE

The present study is designed to investigate the cellular expressions and immunolocalizations of three different nitric oxide synthase (NOS) isoforms and the related nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) signaling pathway in the ovaries of neonatal and immature rats.

METHODS

The ovaries were obtained from ICR (Institute for Cancer Research) female Sprague-Dawley rats at postnatal days 1, 5, 7, 10, and 19. Then we carried out the histologic examination, immunohistochemistry, measurement of NOS activity, and modifications within the NO/cGMP pathway.

RESULTS

During postnatal days 1, 5, 7, 10, and 19, all three isoforms of NOS were mainly localized to the oocytes and expressed as a gradual increase in granulosa cells and theca cells within the growing follicle. The ovarian total NOS activities and NO levels were increased at postnatal days 7 and 10 compared with other days.

CONCLUSIONS

Our findings suggest that the locally produced NO and the NO/NOS signaling systems are involved in the follicular development to puberty.

Effect of the relation between neural cholinergic action and nitric oxide on ovarian steroidogenesis in prepubertal rats

The coeliac ganglion and the ovary are related by the superior ovarian nerve, which penetrates into the ovary by the hilium and innervates mainly the ovarian stroma. On the other hand, it is known that the gaseous neurotransmitter nitric oxide (NO) and the two isoforms of its synthesis enzyme, the nitric oxide synthetase (NOS), are present in the ovary. Both innervation and NO participate in ovarian steroidogenesis. Therefore, the purposes of this work were (a) to standardize an in vitro coeliac ganglion-superior ovarian nerve-ovary integrated system in prepubertal rats; (b) to determine the presence of NO in the ovary and analyze the ganglionic cholinergic effect on the ovarian release of androstenedione, progesterone and NO; and (c) to assess the steroids/NO relationship. The system was incubated in buffer solution for 120 min, with the ganglion and ovary located in different compartments and linked by the superior ovarian nerve. From the results obtained, it is concluded that the system is viable and functional. The presence of basal NO is stimulated by the cholinergic action, while the release of the steroids is inhibited, which might indicate that the ganglionic cholinergic effect is probably mediated by NO. To our knowledge, this work constitutes the first study of the relationship between the neural cholinergic action and NO on the ovarian steroidogenesis of prepubertal rats.

Intrinsic neurons in the mammalian ovary

Mammalian ovarian function is under endocrine and neural control. Although the extrinsic innervation of the ovary has been implicated in the control of both ovarian development and mature function, it is now clear that, from rats to humans, the ovary is endowed with a network of intrinsic neurons displaying diverse chemical phenotypes. This article describes the presence of these intrinsic neurons in the ovary of different mammalian species, and discusses the possible functions that they may have in the regulation of ovarian physiology.

Inducible nitric oxide synthase expression by peritoneal macrophages in endometriosis-associated infertility

OBJECTIVE

Determine whether peritoneal macrophages from women with endometriosis-associated infertility express more inducible nitric oxide synthase (NOS2) and produce more NO than fertile controls.

DESIGN

Unblinded clinical study.

PATIENT(S)

Nine infertile women with endometriosis and nine normal fertile women undergoing laparoscopy.

INTERVENTION(S)

Peritoneal fluid and macrophages were collected. Cells were also cultured with the NOS2 inducers interferon-alpha (IFN-alpha) or IFN-gamma plus lipopolysaccharide (LPS).

MAIN OUTCOME MEASURE(S)

Peritoneal fluid NO levels, peritoneal macrophage NOS activity, and peritoneal macrophage NOS2 protein expression.

RESULT(S)

NOS enzyme activity was higher in peritoneal macrophages from endometriosis patients. Immunoblots demonstrated NOS2 protein only in peritoneal macrophages from women with endometriosis. Peritoneal fluid NO concentration was similar in the two groups, but total peritoneal fluid NO content was higher in endometriosis patients. After 3 days' culture, peritoneal macrophages from women with endometriosis produced more NO in response to IFN-alpha or IFN-gamma plus LPS than controls.

CONCLUSION(S)

Peritoneal macrophages from women with endometriosis-associated infertility express higher levels of NOS2, have higher NOS enzyme activity, and produce more NO in response to immune stimulation in vitro. As high levels of NO adversely affect sperm, embryos, implantation, and oviductal function, reducing peritoneal fluid NO production or blocking NO effects may improve fertility in women with endometriosis.

Inducible and endothelial nitric oxide synthase: genetic background affects ovulation in mice

OBJECTIVE

Inducible nitric oxide synthase (NOS) and endothelial NOS are involved in female reproductive physiology. We sought to investigate the influence of the inducible (Nos2) and endothelial (Nos3) NOS genes as a function of genetic background on ovulatory capacity and early embryonic development in a mouse model.

DESIGN

Observational study of genetically altered mice and their response to a superovulation protocol.

SETTING

Academic research institution.

ANIMALS

Wild-type mice and mice deficient for Nos2 or Nos3 were bred to C57BL/6J and 129/Sv genetic backgrounds.

INTERVENTION(S)

Superovulation protocol, oocyte culture.

MAIN OUTCOME MEASURE(S)

Number of oocytes harvested, early embryonic development of zygotes, evaluation of ovarian histology.

RESULT(S)

The mean number of oocytes was significantly reduced in Nos3 deficient mice on a C57BL/6J background compared with controls. Oocytes deficient for Nos3 on a C57BL/6J background also showed reduced progression to two-cell stage embryos after 24 hours, two-cell stage embryos to blastocyst stage embryos, and survival to 48 hours. Those effects were distinctly absent in mice deficient for Nos3 on a 129/Sv background and in mice deficient for Nos2 on either genetic background.

CONCLUSION(S)

Our data show that disruption of Nos2 had no effect on ovulation in our mice. The negative effect of Nos3 deficiency on ovulatory capacity and early embryonic development is modulated by genetic background. This suggests a role for strain-specific modifier genes in these processes.

Nitric oxide and the control of reproduction

The free radical gas, nitric oxide is now known to be an important biological messenger in animals. Signal transmission by a gas that is produced by one cell, penetrates through membranes and regulates the function of another cell, represents new principles for signalling in biological systems. Nitric oxide is synthesised from L-arginine by enzyme nitric oxide synthase, which exists in multiple isoforms in a wide range of mammalian cells. Studies conducted in recent years point at a strong influence of NO in a wide range of reproductive functions. It is implicated in the control of gonadotrophin secretion at both hypothalamic and hypophyseal levels, LH surge mechanism, sexual behaviour, estradiol synthesis, follicle survival and ovulation. While considerable work lies ahead in unravelling the role of NO at the peripheral, cellular and molecular level in the domestic animal reproduction, findings presented in this review provide a general overview of growing appreciation of NO as a vital molecule controlling hypothalamic-pituitary-gonadal (HPG) axis.

Abnormal estrous cyclicity after disruption of endothelial and inducible nitric oxide synthase in mice

The roles of nitric oxide (NO) and nitric oxide synthase (NOS) in reproduction were studied by examining the estrous cycle of wild-type (WT) mice, inducible NOS (iNOS)-, and endothelial NOS (eNOS)-knockout mice. We observed an average estrous cycle of 4.8 +/- 0.2 days in WT mice. While we observed no significant influence of iNOS deficiency on cycle length, eNOS-knockout females showed a significantly longer estrous cycle (6.6 +/- 0.6 days; p < 0.03) than WT females, due to an extension of diestrus (p < 0.03). There was no influence of iNOS deficiency on ovulation rate compared with that in WT females; however, eNOS-knockout mice showed a significant reduction (p < 0.05) in ovulatory efficiency relative to WT or iNOS-knockout females. In contrast to WT females, in which the highest level of estradiol (E2) was observed at 1500 h of proestrus, iNOS-knockout females reached a peak of E2 at 1830 h of proestrus. In eNOS-knockout females, the peak of E2 occurred at 1830 h, as in iNOS-knockout mice; however, E2 levels were 5-fold and 3-fold higher (p < 0.05) than levels observed in WT and iNOS-knockout females, respectively. There was no effect of genotype on the plasma LH concentrations at proestrus. On the first day of diestrus, eNOS-knockout females showed significantly higher plasma E2 and progesterone levels (p < 0.05) relative to WT and iNOS-knockout females. The dysfunction in cyclicity, ovulation rate, ovarian morphology, and steroidogenesis in eNOS-knockout female mice strongly supports the concept that eNOS/NO plays critical roles in ovulation and follicular development.

Localization of nitric oxide-related substances in the quail ovary during folliculogenesis

In the present study, nitric oxide (NO)-related substances, namely NO synthase (NOS), L-citrulline, cGMP and nitrotyrosine, have been localized in the quail ovary, using NADPH-diaphorase staining and immunohistochemical methods. The results indicate the presence of the NOS isoforms, showing distinct cell-specific distribution patterns in the quail ovary. Inducible NOS is primarily present in leukocytes, endothelial NOS in granulosa cells, and neuronal NOS in nerve cells, oocytes, interstitial cells and granulosa cells of pre-hierarchal follicles and of the germinal disc region of pre-ovulatory follicles. NOS activity, indicated by the presence of L-citrulline, is observed in oocytes, nerve cells, interstitial cells and a few granulosa cells of pre-hierarchal follicles. Detection of accumulated cGMP indicates that granulosa cells of pre-hierarchal and of pre- and post-ovulatory follicles, the theca interna of pre-ovulatory follicles, and oocytes are main targets of NO. Nitrotyrosine, a marker of peroxynitrite activity, is mainly localized in atretic follicles and in post-ovulatory follicles. It is concluded that the quail ovary possesses a NO/NOS system, and that NO may be considered as a mediator involved in various ovarian processes, including atresia.