Inducible nitric oxide synthase is present in the rat placenta at the fetal-maternal interface and decreases prior to labour

Mature Twin Neonates Exhibit Oxidative Stress via Nitric Oxide Synthase Dysfunctionality: A Prognostic Stress Marker in the Red Blood Cells and Umbilical Cord Vessels

Intrauterine hypoxic condition increases the generation of reactive oxygen species and fetal oxidative stress. Multiple pregnancy always bears an additional oxidative stress condition with severe complications, such as prematurity, structural abnormalities, delayed development and low birthweight. The umbilical cord (UC) vessels, along with circulating fetal red blood cells (RBCs), highly determine the oxygenation status of fetus and regulate the feto-placental circulation. As UC lacks innervation, the activation of the endothelial nitric oxide synthase (NOS3) is fundamental for proper NO production. Therefore, we aimed to study the NOS3 activation pathways along with damages to macromolecules in the endothelium of UC vessels and RBCs of mature non-discordant twins, in connection to major differences in their birth weight. We provide evidence that, under severe hypoxic conditions such as twin pregnancy, the NOS3-related NO production pathways are altered both in UC vessels and RBCs; moreover, the extent of changes is highly birthweight-specific. Furthermore, macromolecular damages are prominent in the RBCs and arteries compared to the vein, with a similar increase in the Arginase1 level, which is believed to play a role in NOS3 functionality, resulting in endothelial dysfunctionality, which might have relevance to the major etiologies of cardiovascular diseases in later life.

Efeito do hipotireoidismo materno na expressão espaço-temporal de mediadores imunológicos e população de células natural killers na decídua e na glândula metrial de ratas

RESUMO Estudou-se o efeito do hipotireoidismo materno na expressão espaço-temporal de mediadores imunológicos e na população de células natural killers (NK) na decídua e na glândula metrial de ratas durante a gestação. Avaliou-se a detecção imunoistoquímica de interferon γ (IFNγ), do fator inibidor de migração (MIF), da interleucina 15 (IL15), do óxido nítrico sintase induzível (iNOS), a marcação com lectina DBA para evidenciação das células NK uterinas DBA+ e a expressão gênica de Ifnγ e Nos2. O hipotireoidismo aumentou o iNOS aos sete dias, a IL15 e o MIF aos 10 e 12 dias, o IFNγ e o MIF aos 14 DG e a expressão dos transcritos gênicos para iNos aos 12 e 19 dias e para Ifnγ aos 14 DG. O hipotireoidismo reduziu a imunomarcação de MIF e lectina DBA aos sete dias, lectina DBA aos 10 e 14 DG, IFNγ aos 12 dias, e a expressão de Ifnγ aos 10 e 19 DG e de iNOS aos 12, 14 e 19 DG, bem como reduziu seus transcritos gênicos aos 10 e 14 DG. Conclui-se que o hipotireoidismo compromete o perfil imunológico na interface materno-fetal ao longo da gestação, particularmente por reduzir o fator anti-inflamatório iNOS e a população de células uNK DBA+.

Effect of sildenafil citrate treatment in the eNOS knockout mouse model of fetal growth restriction on long-term cardiometabolic outcomes in male offspring

Fetal growth restriction (FGR) is associated with an increased risk of hypertension, insulin resistance, obesity and cardiovascular disease in adulthood. Currently there are no effective treatments to reverse the course of FGR. This study used the eNOS knockout mouse (eNOS^-/-), a model of FGR, to determine the ability of sildenafil, a potential new treatment for FGR, to improve cardiovascular and metabolic outcomes in adult offspring following a complicated pregnancy. Pregnant eNOS^-/- and C57BL/6J control dams were randomised to sildenafil treatment (0.2 mg/ml in drinking water) or placebo at day 12.5 of gestation until birth. After weaning, male offspring were randomised to either a high fat (HFD; 45% kcal from fat) or normal chow diet (ND), and raised to either postnatal day 90 or 150. Growth and body composition, glucose tolerance, insulin resistance, systolic blood pressure and vascular function were analysed at both time-points. eNOS^-/- offspring were significantly smaller than their C57BL/6J controls at weaning and P90 (p < 0.01); at P150 they were a similar weight. Total adipose tissue deposition at P90 was significantly increased only in eNOS^-/- mice fed a HFD (p < 0.001). At P150 both C57BL/6J and eNOS^-/- offspring fed a HFD demonstrated significant adipose tissue deposition (p < 0.01), regardless of maternal treatment. Both diet and maternal sildenafil treatment had a significant effect on glucose tolerance. Glucose tolerance was significantly impaired in eNOS^-/- mice fed a HFD (p < 0.01); this was significant in offspring from both sildenafil and vehicle treated mothers at P90 and P150. Glucose tolerance was also impaired in C57BL/6J mice fed a HFD at both P90 and P150 (p < 0.01), but only in those also exposed to sildenafil. In these C57BL/6J mice, sildenafil was associated with impaired insulin sensitivity at P90 (p = 0.020) but increased insulin resistance at P150 (p = 0.019). Exposure to sildenafil was associated with a significant increase in systolic blood pressure in eNOS^-/- mice compared with their C57BL/6J diet controls at P150 (p < 0.05). Exposure to sildenafil had differing effects on vascular function in mesenteric arteries; it increased vasodilation in response to ACh in C57BL/6J mice, but was associated with a more constrictive phenotype in eNOS^-/- mice. eNOS^-/- mice demonstrate a number of impaired outcomes consistent with programmed cardiometabolic disease, particularly when faced with the 'second hit' of a HFD. Exposure to sildenafil treatment during pregnancy did not increase fetal growth or significantly improve adult metabolic or cardiac outcomes. Maternal sildenafil treatment was, however, associated with small impairments in glucose handling and an increase in blood pressure. This study highlights the importance of understanding the long-term effects of treatment during pregnancy in offspring from both complicated and healthy control pregnancies.

Therapeutic benefit of mesenchymal stem cells in pregnant rats with angiotensin receptor agonistic autoantibody-induced hypertension: Implications for immunomodulation and cytoprotection

Immunomodulation by mesenchymal stem cells (MSCs) is potentially important for maintaining peripheral tolerance. Preeclampsia may be due to maternal immune rejection of the genetically foreign fetus. This study aimed to investigate the biological function of human umbilical cord-derived mesenchymal stem cells (HU-MSCs) for the treatment of angiotensin receptor agonistic autoantibody (AT1-AA)-induced hypertension during pregnancy. HU-MSCs were isolated, cultured, and labeled in vitro. AT1-AA and HU-MSCs were administered to pregnant rats. Green fluorescent protein (GFP)-positive HU-MSCs infused in vivo were identified by immunofluorescence. Systolic blood pressure (SBP) was evaluated. The effects of HU-MSCs on fetal weight, kidney burden, and spiral artery remodeling, as well as on the expression of tumor necrosis factor α (TNF-α), interleukin 10 (IL-10), and heme oxygenase 1 (HO-1), were investigated. The SBP levels in the HU-MSC-treated pregnant hypertension rats decreased by gestational day 19. The reduction in fetal weight was largely ameliorated after HU-MSC treatment. Lesion burden in the kidney was attenuated and spiral artery remodeling was improved in HU-MSC-treated pregnant hypertension rats. However, green fluorescent protein (GFP)-labeled cells were sparingly observed in the kidney and placenta. Intravenous infusion of HU-MSCs into AT1-AA-induced rats significantly downregulated serum TNF-α levels and upregulated IL-10 levels, concomitant with increased placenta and mesometrial triangle (MT) HO-1 expression. Taken together, intravenous infusion of HU-MSCs ameliorates AT1-AA-induced pregnancy hypertension, intrauterine growth retardation, kidney impairment, and spiral artery remodeling impairment. Moreover, the potential benefits of HU-MSCs may be attributable to both an interference with the pathogenic immune response and a paracrine cytoprotective action.

Oxytocin, its antagonist Atosiban, and preterm labor: a role for placental nitric oxide

OBJECTIVE

The aim of the present study was to understand the role played by Atosiban, an oxytocin receptor antagonist, on trophoblastic human cells, and the molecular bases of its efficacy and safety in the treatment of preterm labor. NO, peroxinitrite production and NOS expression have been evaluated on placenta obtained from term and preterm labors.

PATIENTS AND METHODS

We studied trophoblast cells isolated from selected placental tissue from 20 controls and 20 preterm patients after cesarean sections. Each sample was studied at basal state and after 2 hours incubation with oxytocin and Atosiban.

RESULTS

Significant variations of NO levels, peroxynitrite production and iNOS and eNOS expression both in the preterm, term samples and in each of the considered groups were observed. In the control group Atosiban re-established NO levels that were reduced after incubation with oxytocin, while in preterm samples NO levels were not only re-established but, after incubation with Atosiban, significantly increased compared to basal levels.

CONCLUSIONS

This confirms the beneficial role of Atosiban in prolonging the pregnancy of spontaneous labor at very early gestational periods. In conclusion, Atosiban might be an effective drug to prevent preterm labor, in the therapeutic approach to this pathology.

Obesity, insulin resistance, and skeletal muscle nitric oxide synthase

The molecular mechanisms responsible for impaired insulin action have yet to be fully identified. Rodent models demonstrate a strong relationship between insulin resistance and an elevation in skeletal muscle inducible nitric oxide synthase (iNOS) expression; the purpose of this investigation was to explore this potential relationship in humans. Sedentary men and women were recruited to participate (means ± SE: nonobese, body mass index = 25.5 ± 0.3 kg/m(2), n = 13; obese, body mass index = 36.6 ± 0.4 kg/m(2), n = 14). Insulin sensitivity was measured using an intravenous glucose tolerance test with the subsequent modeling of an insulin sensitivity index (S(I)). Skeletal muscle was obtained from the vastus lateralis, and iNOS, endothelial nitric oxide synthase (eNOS), and neuronal nitric oxide synthase (nNOS) content were determined by Western blot. S(I) was significantly lower in the obese compared with the nonobese group (~43%; P < 0.05), yet skeletal muscle iNOS protein expression was not different between nonobese and obese groups. Skeletal muscle eNOS protein was significantly higher in the nonobese than the obese group, and skeletal muscle nNOS protein tended to be higher (P = 0.054) in the obese compared with the nonobese group. Alternative analysis based on S(I) (high and low tertile) indicated that the most insulin-resistant group did not have significantly more skeletal muscle iNOS protein than the most insulin-sensitive group. In conclusion, human insulin resistance does not appear to be associated with an elevation in skeletal muscle iNOS protein in middle-aged individuals under fasting conditions.

High iNOS mRNA and protein localization during late pregnancy suggest a role for nitric oxide in mouse pubic symphysis relaxation

Remodeling and relaxation of the mouse pubic symphysis (PS) are central events in parturition. The mouse PS remodels in a hormone-controlled process that involves the modification of the fibrocartilage into an interpubic ligament (IpL), followed by its relaxation prior to parturition. It is recognized that nitric oxide synthase (NOS) and consequently nitric oxide (NO) generation play important roles in extracellular matrix modification, and may promote cytoskeleton changes that contribute to the remodeling of connective tissue, which precedes the onset of labor. To our knowledge, no studies thus far have investigated inducible nitric oxide synthase (iNOS) expression, protein localization, and NO generation in the mouse PS during pregnancy. In this work, we used a combination of the immunolocalization of iNOS, its relative mRNA expression, and NO production to examine the possible involvement of iNOS in remodeling and relaxation of the mouse IpL during late pregnancy. The presence of iNOS was observed in chondrocytes and fibroblast-like cells in the interpubic tissues. In addition, iNOS mRNA and NO production were higher during preterm labor on Day 19 of pregnancy (D19) than NO production on D18 or in virgin groups. The significant increase in iNOS mRNA expression and NO generation from the partially relaxed IpL at D18 to the completely relaxed IpL at D19 may indicate that NO plays an important role in late pregnancy during relaxation of the mouse IpL.

Expression levels of cyclooxygenase-2, tumor necrosis factor-α and inducible NO synthase in placental tissue of normal and preeclamptic pregnancies

OBJECTIVE

Although preeclampsia (PE) is one of the most important problems affecting pregnant women, etiologic factors in its development are still unclear. We aimed to investigate the expression levels of cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α) and inducible NO synthase (iNOS) in preeclamptic and healthy control placentas.

PATIENTS AND METHODS

Placental tissue samples were obtained after delivery from patients diagnosed with PE and from normal-term pregnants and analyzed for COX-2, TNF-α and iNOS expression by immunohistochemistry.

RESULTS

A strong expression of COX-2 was observed in syncytiotrophoblast cells of preeclamptic placentas, which was significantly higher than that of normal placentas (p = 0.005). A mild expression of TNF-α in both normal and preeclamptic syncytiotrophoblasts was seen (p = 0.435). In addition, a strong expression of iNOS in normal syncytiotrophoblasts was found, but the intensity of the iNOS expression was highly reduced in preeclamptic placentas (p = 0.001). No correlation was detected between COX-2, TNF-α and iNOS expression levels.

CONCLUSION

The findings of a decrease of iNOS expression and an increase of COX-2 expression in placenta suggest the existence of functional roles of iNOS and COX-2 in the pathophysiology of PE, probably by contributing to the reduced placental blood flow and increased resistance to flow in the fetomaternal circulation.

Evaluation of placental protein modifications in normotensive and spontaneously hypertensive rats

Hypertension in pregnancy is often associated to placental deficiency. Therefore several physiopathological modifications occur to sustain fetal well-being through protective mechanisms. Here, we used spontaneously hypertensive rat (SHR) and normotensive Wistar-Kyoto (WKY) counterpart to evaluate in late gestation (d 20) modification of placental proteins involved in adaptation to hypertension. Placenta from WKY and SHR was excised for the evaluation of protein changes by Western blot analysis and zymography. In particular, we showed in SHR placentas an increase in angiotensin receptor type 1 and a decrease in angiotensin converting enzyme. Conversely, inducible nitric oxide synthase expression was increased, while constitutive endothelial nitric oxide synthase was similar in both groups. Placentas from SHR showed a reduced protein expression in both peroxisome proliferators-activated receptors-alpha and -gamma. Pro-metalloproteinase-9 activity was not significantly modified, whereas both pro-metalloproteinase-2 and its active form present a higher activity in SHR placentas. Moreover, at the end of pregnancy, cyclooxygenase-2 expression decreased in SHR placentas. These data may provide new insights into the placental adaptive mechanisms that take place during pregnancy in SHR.

Signaling molecules involved in IFN-gamma-inducible nitric oxide synthase expression in the mouse trophoblast

PROBLEM

We have previously shown that trophoblast can generate nitric oxide (NO) and express inducible isoform of nitric oxide synthase (iNOS). Moreover, this production was changed by the presence of interferon-gamma (IFN-gamma) establishing a relationship between trophoblast inductive response and this proinflammatory cytokine.

METHOD OF STUDY

As the intracellular signal transduction pathway used by IFN-gamma in target cells is the Janus kinase (JAK)-signal transducer and transcription activator (STAT), here we analyzed in the mouse trophoblast the effect of IFN-gamma and staurosporine on mRNA and protein expressions of IFN-gamma signaling molecules correlating them with iNOS expression.

RESULTS

Interferon-gamma induced iNOS expression and upregulated Jaks and Stat1, but not Stat2 transcriptions. The protein distribution matched the mRNA expression pattern. These effects were abrogated when IFN-gamma receptor was blocked by staurosporine.

CONCLUSION

Due to the biological effects of NO-iNOS generated on induction of apoptosis and inflammatory responses, interaction between iNOS expression and IFN-gamma-mediated signaling is very important for understanding the physiology of trophoblast at the maternal-fetal interface. Our data indicate IFN-gamma acts specifically on trophoblast, regulating the expression of signaling molecules and is fundamental for iNOS expression.

Effect of Placental Fatty Acid Metabolism and Regulation by Peroxisome Proliferator Activated Receptor on Pregnancy and Fetal Outcomes

Fatty acids, particularly the omega-3 and omega-6 essential fatty acids (EFAs), are considered critical nutritional sources for the developing fetus. The placenta governs the fetal supply of fatty acids via two processes: transport and metabolism. Placental fatty acid metabolism can play a critical role in guiding pregnancy and fetal outcome. EFAs can be metabolized to important cell signaling molecules in placenta by several major isoform families including: the Cytochrome P450 subfamily 4A (CYP4A); Cyclooxygenases (COXs); and Lipoxygenases (LOXs). Peroxisome proliferator-activated nuclear receptors (PPARs) have been demonstrated to regulate a number of placental fatty acid/lipid homeostasis-related proteins (e.g., metabolizing enzymes and transporters). The present review summarizes research on the molecular and functional relevance of fatty acid metabolizing enzymes and the role of PPARs in regulating their expression in the mammalian placenta. Elucidating the pathways of placental fatty acid metabolism and the regulatory processes governing these pathways is critical for advancing our understanding of the role of placenta in supplying EFAs to the developing fetus and the potential implications on pregnancy and fetal outcome. A more complete understanding of placental fatty acid disposition may also provide a basis for nutritional/pharmacological interventions to ameliorate the risk of adverse pregnancy and/or fetal outcomes.

Prostaglandins and reproduction in female farm animals

Prostaglandins impact on ovarian, uterine, placental, and pituitary function to regulate reproduction in female livestock. They play important roles in ovulation, luteal function, maternal recognition of pregnancy, implantation, maintenance of gestation, microbial-induced abortion, parturition, postpartum uterine and ovarian infections, and resumption of postpartum ovarian cyclicity. Prostaglandins have both positive and negative effects on reproduction; they are used to synchronize oestrus, terminate pseudopregnancy in mares, induce parturition, and treat retained placenta, luteinized cysts, pyometra, and chronic endometritis. Improved therapeutic uses for prostaglandins will be developed when we understand better their involvement in implantation, maintenance of luteal function, and establishment and maintenance of pregnancy.

Protection from abortion by heme oxygenase-1 up-regulation is associated with increased levels of Bag-1 and neuropilin-1 at the fetal-maternal interface

Tolerance mechanisms allowing pregnancy success resemble those involved in allograft acceptance. Heme oxygenase (HO) is a tissue-protective molecule, which allows graft acceptance and is known to have antiapoptotic effects on several cell types. We previously reported down-regulated levels of HO-1 and HO-2 in placenta from allopregnant mice undergoing abortion. In this study, we analyzed whether the up-regulation of HO-1 by cobalt-protoporphyrin (Co-PP) during implantation window can rescue mice from abortion. Induction of HO-1 by Co-PP treatment prevented fetal rejection, whereas the down-regulation of HOs by zinc-protoporphyrin application boosted abortion. The beneficial effect of HO-1 induction was not related to a local shift to Th2-profile or to a change in the NO system. Interestingly, the expression of the antiapoptotic/cytoprotective molecule Bag-1 as well as the levels of neuropilin-1, a novel marker for T regulatory cells, were up-regulated after Co-PP treatment. Our data strongly support a very important role for HO-1 in fetal allotolerance and suggest that HO-1 might be protective by up-regulating tissue protective molecules, i.e., Bag-1, and by activating T regulatory cells rather than by changing the local cytokine profile.

Is nitric oxide luteolytic or antiluteolytic?

Nitric oxide (NO) has been reported to be luteolytic based on treatment of cows in vivo with an inhibitor of nitric oxide synthase (NOS-produces NO), which delayed the decline in progesterone by two to three days [Jaroszewki J, Hansel, W. Intraluteal administration of a nitric oxide synthase blocker stimulates progesterone, oxytocin secretion and prolongs the life span of the bovine corpus luteum. Proc Soc Exptl Biol Med 2000;224:50-5; Skarzynski D, Jaroszewki J, Bah, M, et al. Administration of nitric oxide synthase inhibitor counteracts prostaglandin F(2alpha)-induced luteolysis in cattle. Biol Reprod 2003;68:1674-81]. The objective of this experiment was to determine the effect of a long acting NO donor or a NOS inhibitor infused chronically into the interstitial tissue of the ovarian vascular pedicle adjacent to the ovary with a corpus luteum on secretion of progesterone during the ovine estrous cycle. Ewes were treated either with Vehicle (N=5); Diethylenetriamine (DETA-control for DETA-NONOate; N=5); (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl) amino]diazen-1-ium-1,2-diolate (DETA-NONOate-long acting NO donor; N=6); or l-nitro-arginine methyl ester (l-NAME-NOS inhibitor; N=6) every 6 h from 24:00 h (0 h) on day 8 through 18:00 h on day 18 of the estrous cycle. Jugular venous blood was collected every 6h for analysis for progesterone and corpora lutea were collected at 18:00 h on day 18 and weighed. Weights of corpora lutea were heavier (P< or =0.05) in DETA-NONOate-treated ewes when compared to Vehicle, DETA, or l-NAME-treated ewes, which did not differ amongst each other (P> or =0.05). Profiles of progesterone in jugular venous blood on days 8-18 differed (P< or =0.05) in DETA-NONOate-treated ewes when compared to Vehicle, DETA, or l-NAME-treated ewes did not differ (P> or =0.05) amongst each other. It is concluded that NO is not luteolytic during the ovine estrous cycle, but may instead be antiluteolytic and prevent luteolysis.

In vivo progestin treatments inhibit nitric oxide and endothelin-1-induced bovine endometrial prostaglandin (PG) E (PGE) secretion in vitro

Synchronization of estrus with progestins in cows has been reported to inhibit nitric oxide (NO) and endothelin-1 (ET-1)-stimulated bovine luteal PGE secretion without affecting prostaglandin F2alpha (PGF2alpha) secretion in vitro [Weems YS, Randel RD, Tatman S, Lewis A, Neuendorff DA, Weems CW. Does estrous synchronization affect corpus luteum (CL) function? Prostaglandins Other Lipid Mediat 2004;74:45-59]. Two experiments were conducted to determine the effects of NO donors, endothelin-1 (ET-1), and NO synthase (NOS) inhibitors on bovine caruncular endometrial secretion of PGE and PGF2alpha in vitro. In Experiment 1, estrus was synchronized in Brahman cows with Synchromate-B ear implants, which contained the synthetic progestin norgestamet. Days 14-15 caruncular endometrial slices were weighed, diced, and incubated in vitro with treatments. Treatments (100 ng/ml) were: Vehicle (control), l-NAME (NOS inhibitor), l-NMMA (NOS inhibitor), DETA (control), DETA-NONOate (NO donor), sodium nitroprusside (NO donor), or ET-1. In Experiment 2, estrus was synchronized in Brahman cows with either Lutalyse (PGF2alpha) or a controlled intravaginal drug releasing device (CIDR-containing progesterone) or estrus was not synchronized. Days 14-15 caruncular endometrial slices were weighed, diced, and incubated in vitro with treatments. Treatments (100 ng/ml) were: vehicle, l-NAME, l-NMMA, DETA, DETA-NONOate, sodium nitroprusside, SNAP (NO donor) or ET-1. Tissues were incubated in M-199 for 1h without treatments and with treatments for 4 and 8h in both experiments. Media were analyzed for concentrations of PGE and PGF2alpha by radioimmunoassay (RIA). Hormone data in Experiments 1 and 2 were analyzed by 2x7 and 3x2x8 factorial design for ANOVA, respectively. Concentrations of PGE and PGF2alpha in media increased (P< or =0.05) from 4 to 8 h regardless of treatment group in Experiment 1, but did not differ (P> or =0.05) among treatments. In Experiment 2, concentrations of PGE and PGF2alpha increased (P< or =0.05) with time in all treatment groups of all three synchronization regimens. DETA-NONOate, SNAP, and sodium nitroprusside (NO donors) and ET-1 increased caruncular endometrial (P< or =0.05) secretion of PGE2 in unsynchronized and Lutalyse synchronized cows, but not when estrus was synchronized with a CIDR (P> or =0.05). No treatment increased (P> or =0.05) PGF2alpha in any synchronization regimen. It is concluded that norgestamet in Synchromate-B ear implants or progesterone in a CIDR alters NO or ET-1-induced secretion of PGE by bovine caruncular endometrium and could interfere with implantation by altering the PGE:PGF2alpha ratio resulting in increased embryonic losses during early pregnancy.

Nitric oxide synthase in human skeletal muscles related to defined fibre types

Skeletal muscle functions regulated by NO are now firmly established. However, the knowledge about the NO synthase (NOS) expression related to a defined fibre type in human skeletal muscles necessitates further clarification. To address this issue, we examined localization of NOS isoforms I, II and III, in human skeletal muscles employing immunocytochemical labeling with tyramide signal amplification complemented with enzyme histochemistry and Western blotting. The NOS immunoreactivity was related to fibre types of different classification systems: physiological classification into slow and fast, ATPase classification into I, IIA, IIAX, IIX, and physiological-metabolic classification into slow-oxidative (SO), fast-oxidative glycolytic (FOG) and fast-glycolytic (FG). We found a correlation of NOS I-III immunoreactivity to metabolic defined fibre types with strong expression in FOG fibres. This implies that NO as modulator of muscle function is involved in oxidative metabolism in connection with fast force development, which only occurs in FOG fibres. The NOS expression showed no correlation to ATPase fibre subtypes due to the metabolic heterogeneity of ATPase fibre types. Healthy and affected vastus medialis muscles after anterior cruciate ligament rupture revealed similar NOS expression level as shown by Western blotting with, however, different expression patterns related to the fibre types in affected muscles. This suggests an altered modulation of force development in the fibres of diseased muscles.

Heme oxygenase as a therapeutic target in immunological pregnancy complications

The allogeneic fetus has been considered to be an allograft and the tolerance mechanisms involved in pregnancy maintenance resemble those leading to graft acceptance. Up-regulation of Heme Oxygenase-1 (HO-1) promotes graft acceptance. Additionally, HO-1 has been proposed to have tissue-protective properties. Previous studies reported the presence of HO-1 and HO-2 in mammalian placenta and postulated a protective role for HO during pregnancy. Here, we analyze HO-1 and HO-2 expression at the feto-maternal interface from normal pregnant and abortion mice and correlate these findings with inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) expression as well as with Th1/Th2 cytokine production by immune cells. DBA/2-mated CBA/J females undergoing abortion and BALB/c-mated CBA/J females having normal pregnancies were included in our study. The mice received no treatment. On day 14 of pregnancy, the mice were sacrificed, the abortion rate was calculated and the ex vivo Th1/Th2 production by decidual immune cells was analyzed by flow cytometry. The expression of HO-1 and HO-2, iNOS and eNOS was analyzed by immunohistochemistry (IHC) and Western blot in placenta samples. The Th1/Th2 cytokines ratio was augmented in decidua from abortion mice. We further observed a significant down-regulation of HO-1, HO-2, iNOS and eNOS molecules in placental tissue from mice undergoing abortion when compared to normal pregnant mice. Since we found diminished HOs and nitric oxide synthase (NOS) levels at the feto-maternal interface from abortion mice when compared to normal pregnant mice, which were further associated with increased Th1/Th2 cytokine production, we propose HO as a putative therapeutic target in immunological abortions. Up-regulation of HO-1 or HO-2 would favour the Th2-cytokine production, which could avoid abortion onset.

Expression of endothelial NO synthase, inducible NO synthase, and estrogen receptors alpha and beta in placental tissue of normal, preeclamptic, and intrauterine growth-restricted pregnancies

In the physiology of placental blood circulation, nitric oxide (NO) synthases seem to play important roles, although their expression in pathological placentas and their role is still unclear. In addition, NO synthase activation seems to be related to estrogen receptor expression. Therefore, the aims of this study were to investigate the expression of estrogen receptors alpha (ERalpha), estrogen receptor beta (ER and the endothelial NO synthase (eNOS), and inducible NO synthase (iNOS) in intrauterine growth-restricted (IUGR) placentas, preeclamptic placentas, and in normal healthy control placentas. Slides of paraffin-embedded placental tissue were obtained after delivery from patients diagnosed with IUGR, preeclampsia, and normal term placentas and analyzed for eNOS, iNOS as well as ERalpha and ERbeta expression. Intensity of immunohistochemical reaction was analyzed using a semiquantitative score and statistical analysis was performed. In addition, Western blot experiments were performed for comparison of staining intensities obtained by immunohistochemistry and western blot. Expression of eNOS, iNOS, and ERbeta is significantly reduced in trophoblast cells of placentas with IUGR. However, preeclamptic placentas demonstrated a significant elevated expression intensity of these proteins compared with normal controls. A different expression of eNOS, iNOS, ERalpha, and ERbeta by human trophoblast cells seems to results in lower NO output and impaired trophoblast invasion. Results obtained in our study provide evidence that reduced expression of the investigated proteins is related to IUGR.

Expression of CYP4A isoforms in developing rat placental tissue and rat trophoblastic cell models

Maintaining fatty acid homeostasis during pregnancy is critical for normal fetal development. As an organ that controls nutrient supply from the mother to the fetus, the placenta plays a significant role in guiding fatty acid transfer to the developing fetus. The cytochrome P450 4A (CYP4A) subfamily of metabolizing enzymes is a group of structurally and functionally conserved proteins that are specialized in the omega/omega-1 hydroxylation of saturated and unsaturated fatty acids and their derivatives. To understand the function of the CYP4A system in the placenta and its significance in maintaining fetal fatty acid homeostasis, information about the placental expression of individual CYP4A isoforms is required. In the present study, we have elucidated the temporal and spatial patterns of expression of the four known rat CYP4A isoforms (CYP4A1, CYP4A2, CYP4A3, and CYP4A8) in the junctional and labyrinthine zones of the developing rat chorioallantoic placenta as well as two rat trophoblastic cell lines, HRP-1 and Rcho-1, using semi-quantitative RT-PCR and immunohistochemical analyses. The mRNA from the four rat CYP4A isoforms was detected in the developing rat placenta with CYP4A1 exhibiting the strongest expression (4A1 > 4A2 >> 4A3 approximately equal to 4A8). CYP4A1 was also detected by immunohistochemical staining in the developing rat placenta. We also observed CYP4A1 in both HRP-1 and Rcho-1 cells by RT-PCR, suggesting the utility of these cells as in vitro tools to study the effects of xenobiotics on placental fatty acid metabolism. Establishing the expression of CYP4A isoforms in these tissues and cell models provides a framework for further investigation of their functional and physiological significance in guiding proper fetal development.

Effects of estrous synchronization on response to nitric oxide donors, nitric oxide synthase inhibitors, and endothelin-1 in vitro

Two experiments were conducted to determine the effects of nitric oxide (NO) donors, endothelin-(ET-1), and NO synthase (NOS) inhibitors on bovine luteal function in vitro. In experiment 1, estrus in Brahman cows was synchronized with Synchro-Mate-B (SMB) and day-13-14 corpora luteal slices were weighed, diced and incubated in vitro. Treatments (100 ng/ml) were: vehicle, N[see symbol in text]-nitro-L-arginine-L-methyl ester (L-NAME), N(G)-monomethyl-L-arginine acetate (L-NMMA), diethylenetriamine (DETA), DETA-NONOate, sodium nitroprusside (SNP), or ET-1. In experiment 2, estrus was synchronized with Lutalyse, a Controlled Intravaginal Progesterone Releasing Device (CIDR), or cows were not synchronized. Corpora lutea were collected, weighed, and luteal slices were weighed, diced and incubated in vitro with treatments. Treatments (100ng/ml) were: vehicle, L- NAME, L-NMMA, DETA, DETA-NONOate, sodium nitroprusside, S-nitroso-N-acetylpenicillamine (SNAP) or endothelin-1. Tissues were incubated in M- 199 for 1 h without treatments and for 4 and 8 h in both experiments with treatments in both experiments. Media were analyzed for progesterone, prostaglandins E2 and F2alpha (PGE2, PGF2alpha) by radioimmunoassay (RIA). Hormone data in experiments 1 and 2 were analyzed by 2 x 7 and 3 x 2 x 8 factorial design for analysis of variance (ANOVA), respectively. Luteal weights in experiment 2 were analyzed by a one-way ANOVA. Concentrations of progesterone in media were similar (P > or = 0.05) among treatments within experiments. Concentrations of PGE2 in media in experiment 1 were undetectable in 90 and 57% of the samples at 4 and 8 h, respectively. PGF2alpha increased (P < or = 0.05) with time, but did not differ (P > or = 0.05) among treatments. Secretion of PGF2alpha was not affected by treatments (P > or = 0.05). In experiment 2, luteal weights of the induced estrous cycle were decreased (P < or = 0.05) by Lutalyse. Concentrations of PGE2 and PGF2alpha increased (P < or = 0.05) with time in control of all three synchronization regimens. DETA-NONOate, SNAP, sodium nitroprusside (NO donors) and ET-1 increased (P < or = 0.05) PGE2 except in the CIDR synchronized group (P > or = 0.05). No treatment increased (P > or = 0.05) PGF2alpha in any synchronization regimen. It is concluded that either SMB containing norgestomet or a CIDR containing progesterone alters luteal secretion of PGE2, Lutalyse lowers luteal weights in the induced estrous cycle, and NO or ET-1 given alone are not luteolytic agents. It is suggested that NO and ET-1 could have indirect antiluteolytic/luteotropic effects via increasing PGE2 secretion by luteal tissue rather than being luteolytic.

Synergistic effects of antiprogestins and iNOS or aromatase inhibitors on establishment and maintenance of pregnancy

Progesterone is known to be involved in many steps in female reproduction including control of implantation and uterine-cervical function during pregnancy. Our studies in rats and guinea pigs indicate that progesterone inhibits uterine contractility and cervical softening during pregnancy. Progesterone levels or actions decline near the end of pregnancy leading to the onset of labor. Treatment with progestin agonists prolongs pregnancy and inhibits cervical softening, whereas treatment with antiprogestins (mifepristone or onapristone) stimulates uterine contractility, cervical softening and premature delivery. Thus the effect of progesterone receptor modulators in the uterus and cervix depend up on the degree of intrinsic agonistic/antagonistic activities. Our recent studies show that progesterone interacts with nitric oxide (NO) to maintain pregnancy and that administration of progesterone antagonists with NO synthase inhibitors act synergistically to stimulate labor. In addition our studies show that combinations of progesterone antagonists with aromatase inhibitors act synergistically to induce labor. Similarly antiprogestins interact with NO synthase or aromatase inhibitors to block implantation through action on the endometrium. These studies suggest new applications for combined therapies of progestin receptor modulators with aromatase inhibitors or agents that modify NO production for contraception, stimulation of labor, estrogen-dependent diseases and improved outcomes in pregnancy.

Nitric oxide synthase activity in human trophoblast, term placenta and pregnant myometrium

To investigate the possible role of nitric oxide (NO) produced locally or intramurally in the quiescence of the pregnant myometrium, nitric oxide synthase (NOS) activity was measured in samples from first trimester (villous, and non villous-trophoblast), term placenta and pregnant myometrium. Trophoblast tissue was obtained from psychosocial termination of pregnancy (9-12 weeks' gestation) whereas placenta and myometrium, from the same patient, at deliveries by Caesarean section. NOS activity was measured in both cytosolic and particulate fractions by the formation of 14C-citrulline from 14C-arginine. Western immunoblotting was used to identify the endothelial NOS (eNOS) and neuronal (nNOS) isoforms. The activity of NOS in particulate fractions from all preparations was considerably higher than the cytosolic fractions. Activity in all fractions except the myometrium was highly Ca-dependent. More than 50% of particulate NOS from the myometrium was Ca-independent. NOS activity was highest in the villous trophoblast and there was a significant difference between the villous and non-villous trophoblast. In placenta and myometrium, NOS was 2-4 fold and 20-28-fold lower than the villous trophoblast, respectively. Western blot analysis showed clearly eNOS in the particulate fraction and a weak eNOS band in the cytosolic fractions, whereas nNOS was not detectable in any of the fractions. In view of the marginal activity of NOS in the myometrium, NO produced by the trophoblast and placenta could play a significant role in maintaining uterine quiescence by paracrine effect.

Important differences in nitric oxide synthase activity and predominant isoform in reproductive tissues from human and rat

For the extrapolation of data obtained from experimental animals to the human situation, it is important to know the similarities and differences between human and animal species. Some important characteristics of nitric oxide synthase (NOS) in myometrium and vagina from human and rat were compared. NOS-activity was measured by the formation of 14C-citrulline from 14C-arginine and the expression of NOS isoforms was examined by Western blotting. NOS activity in human uterus and vagina was significantly lower than in the tissues from rat. In contrast to the rat where NOS activity was predominantly found in the cytosolic fractions, NOS activity in particulate and cytosolic fractions from both human myometrium and vagina was similar. Data from Western blots confirmed that eNOS and nNOS isoforms were concentrated in the particulate and cytosolic fractions, respectively. Estrogen treatment of rats resulted in a down regulation of uterine cytosolic NOS activity. A down regulation of NOS in the cytosolic fraction was also seen in the human pregnant myometrium as compared with the nonpregnant myometrium. The vaginal NOS activity was considerably higher than the uterus in both species. In spite of some clear-cut qualitative and other differences between human and rat tissues, there are some interesting similarities. Downregulation in pregnancy of human uterine NOS is probably due to, at least in part, the influence of estrogen and progesterone.

New developments in the management of preterm labor

Current management of preterm labor has not changed the incidence of preterm delivery; therefore, significant research effort has been concentrated on the search for new methods of management. New tocolytics like inhibitors of cyclooxygenase 2 and nitric oxide donors have been tested in animal models and in preliminary clinical trials with promising results. Inhibition of cervical ripening may be one alternative to tocolysis. This new approach has a potential to be a valuable method of management of preterm labor if human studies confirm the promising results reported in animals. Growing evidence suggests that premature delivery may be associated with infection or fetal growth abnormalities, with dire consequences to the fetus. If these associations are to be included in risk and benefit assessment, then inhibition of preterm labor may prove to be detrimental to the fetus.

NADPH-diaphorase activity and nitric oxide synthase isoforms in the trophoblast of Calomys callosus

The pattern of expression of a variety of placental nitric oxide synthase isoforms has contributed to elucidating the regulatory mechanisms of nitric oxide (NO) synthesis during gestation. The maintenance of vascular tone, attenuation of vasoconstriction, prevention of platelet and leukocyte adhesion to the trophoblast surface, and possible participation in uterine blood flow seem to be the main functions of NO generated at the fetal-maternal interface in humans and mice. Extending this knowledge to other rodent species commonly used as laboratory animals, in this study we focus on NADPH-diaphorase activity and the distribution of nitric oxide synthase isoforms (NOS) in the trophoblast cells of Calomys callosus during different phases of pregnancy. NADPH-diaphorase activity was evaluated cytochemically and the presence of NOS isoforms detected by immunohistochemistry. These techniques were performed on pre- and postimplantation embryos in situ and in vitro, as well as in placentae on d 14 and 18 of pregnancy. Neither NADPH-diaphorase activity nor inducible or endothelial NOS isoforms were found in pre-implanting embryos except after culturing for at least 48 h, when some of the embryonic cells were positive for the diaphorase reaction. On d 6.5 of pregnancy, trophoblast cells showed intense diaphorase activity both in situ and under in vitro conditions. A positive reaction was also found in the different placental trophoblast cells on d 14 and 18 of pregnancy. The inducible NOS (iNOS) isoform, but not the endothelial isoform, was immunodetected in trophoblast cells from the placenta and from postimplantation embryos in situ and under in vitro conditions. These results strongly suggest the production of NO by the iNOS isoform in the trophoblast of Calomys callosus after embryo implantation. The data also emphasise a possible role for the trophoblast in producing and releasing cytotoxic molecules at the fetal-maternal interface.

Expression and localization of inducible nitric oxide synthase in human non-pregnant and early pregnant endometrium

The aim of the present study was to investigate the expression and distribution patterns of inducible nitric oxide synthase (iNOS) in human non-pregnant and early pregnant endometrium using Northern blot analysis, reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. Northern blot analysis revealed the expression of iNOS mRNA in human decidua and chorionic villi in the first trimester but not in the endometrium at any stage of the menstrual cycle. Nested RT-PCR, however, detected iNOS mRNA in human endometrium at all stages of the menstrual cycle. Immunohistochemical staining of the secretory endometrium using an anti-human iNOS polyclonal antibody revealed labelling specifically concentrated in glandular epithelial cells. Staining was absent in stromal cells. However, iNOS staining was positive in decidualized stromal cells in tissues obtained in the first trimester of pregnancy. Furthermore, extensive staining was observed in both syncytiotrophoblastic and cytotrophoblastic cells. The finding of a large amount of iNOS mRNA at the feto-maternal interface throughout the first trimester of pregnancy suggests that iNOS may play an important role in the maintenance of pregnancy.

Participation of the mouse implanting trophoblast in nitric oxide production during pregnancy

While considerable progress has been made in elucidating nitric oxide (NO) regulatory mechanisms in the later stages of gestation, much less is known about its synthesis and role during embryo implantation. Thus, to evaluate the participation of the trophoblast in the production of NO during this phase, this study focused on NADPH-diaphorase activity and the distribution of NO synthase isoforms (NOS) using immunohistochemistry in pre- and postimplantation mouse embryos in situ and in vitro, as well as on NO production itself, measured as total nitrite, in trophoblast culture supernatants (Griess reaction). No NADPH-diaphorase activity was found in preimplanting embryos except after culturing for at least 48 h, when a few trophoblastic giant cells were positive. Conversely, postimplantation trophoblast cells either lodged into the implantation chamber (in situ) or after culturing (in vitro) showed intense NADPH-diaphorase activity. Also in the postimplantation trophoblast, the endothelial and inducible NOS (eNOS and iNOS) isoforms were immunodetected, under both in situ and in vitro conditions, although in different patterns. Extracts of ectoplacental cone also revealed bands of 135 and 130 kDa on SDS-PAGE that reacted with anti-eNOS and anti-iNOS, respectively, on Western blot. Analysis of the culture supernatant demonstrated that the nitrite concentration was 1) proportional to the number of cultured trophoblast cells, 2) almost completely abolished in the presence of N(omega)-nitro-L-arginine methyl ester, and 3) increased 2-fold in cultures stimulated with gamma-interferon. These results strongly suggest the production of NO from constitutive and inducible isoforms of NOS by the implanting mouse trophoblast. They also emphasize the possibility of the participation of these cells in vasodilatation and angiogenesis, and in cytotoxic mechanisms involved in the intense phagocytosis of injured maternal cells, which occur during the implantation process.

Effect of placental tissue on inhibition of uterine contraction by nitric oxide donors

OBJECTIVE

Our purpose was to test the hypothesis that placental tissue modulates the effect of nitric oxide on spontaneous uterine contractility in pregnant rats.

STUDY DESIGN

Rings (approximately 4 mm) of uterus taken from rats on day 14 (midpregnancy, n = 6), day 18 (late pregnancy, n = 4), and day 22 (term, n = 4) of gestation were placed in organ chambers filled with Krebs-bicarbonate buffer bubbled with 5% carbon dioxide in air (37 degrees C, pH approximately 7.4) for isometric tension recording. In some rings a piece of placenta was left attached to the uterine wall. In the other rings the fetuses, placentas, and membranes were removed completely. Change of spontaneous contractions of the rings (percentage change of basal integral activity for 10 minutes) in response to cumulative concentrations of the nitric oxide donors diethylamine-nitric oxide and nitroglycerin (10(-6) mol/L to 10(-4) mol/L) were compared between rings with and without placenta.

RESULTS

Diethylamine-nitric oxide and nitroglycerin inhibited spontaneous uterine contractions in rings from midpregnancy, in both the absence and the presence of placenta. In rings from midpregnancy, the maximal inhibition of contractions by diethylamine-nitric oxide but not by nitroglycerin was significantly (P <.05) higher in the presence (26.7% +/- 3.5% of basal activity) than in the absence (39. 6% +/- 3.3%) of placenta. Inhibition of contraction by nitric oxide donors in rings from late and term pregnancy was less than in midpregnancy, and the presence of placental tissue did not influence the responses.

CONCLUSIONS

The presence of placental tissue enhances inhibition of uterine contractility by agents that spontaneously release nitric oxide, such as diethylamine-nitric oxide, but not by nitroglycerin, which requires metabolic transformation for nitric oxide to be released. Refractoriness to nitric oxide near or at term does not depend on the presence or absence of placental tissue.

Inhibition of nitric oxide production rescues LPS-induced fetal abortion in mice

In this report, we examined the involvement of the cytokines tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, interleukin (IL)-4, and IL-10 as well as nitric oxide (NO) in the lipopolysaccharide (LPS)-induced experimental abortion model in BALB/c mice. Although in vivo administration of LPS in pregnant mice showed a 72% decrease of serum IL-10, no significant difference in serum TNF-alpha, IFN-gamma, and IL-4 levels, compared to controls, could be detected. At the same time, a correlation of fetal abortion and maternal splenomegaly with an important increase of NO synthesis in the serum was obtained. Simultaneous administration of LPS and aminoguanidine (AG; an inhibitor to NO synthase) rescued the LPS-induced fetal abortion, reduced maternal spleen weight to physiological levels, and decreased serum NO concentration to control levels. In vitro experiments showed that LPS directly induced NO production in primary placental cells and the TPOPHO-1 trophoblast cell line by stimulating the inducible isoform of NO synthase, which ultimately could be blocked by the NO synthase inhibitors AG and L-NAME. The results indicate that LPS, despite its beneficial involvement in intracellular infections, participates in inflammatory/autoimmune damage during pregnancy, leading to embryotoxicity, which is closely linked to the NO pathway.

Role of nitric oxide in the uterus and cervix: implications for the management of labor

The results of our experimental studies indicate that that parturition is composed principally of two major phases, a relatively long conditioning (preparatory) phase followed by a short and probably irreversible active labor phase. The major events of conditioning phase are: (i) the progression of uterine contractility from an inactive to a vigorously active state, (ii) cervical ripening, and (iii) activation of fetal membranes. Our experimental and molecular studies indicate that nitric oxide (NO) is an important element in controlling uterine and cervical functions during the transition from pregnancy to the conditioning phase of labor. These studies show that NO acts in concert with progesterone to regulate uterine quiescence and cervical rigidity. In the rat uterus and cervix NO is produced mainly by the cytokine-inducible NO synthase (iNOS) which expression is gestationally-regulated and progesterone-dependent. During pregnancy iNOS expression is up-regulated in the uterus and down-regulated in the cervix. Opposite changes occur during term and antiprogestin-induced preterm labor. Our studies with NOS-inhibitors and NO donors suggest that in the uterus a decrease in NO production contributes to the initiation of labor, whereas in the cervix NO acts as a final metabolic mediator of cervical ripening. The evidence also indicates that NO donors have therapeutic potential as tocolytic agents. On the other hand, locally applied NO donors can be used to induce cervical ripening. In addition iNOS, may represent a new target for novel therapeutic agents capable of promoting or inhibiting uterine of both contractility and cervical ripening. There is an urgent need for controlled studies demonstrating clinical efficacy and safety of NO donors in obstetrics.

Synergistic role of nitric oxide and progesterone during the establishment of pregnancy in the rat

Successful pregnancy is strictly dependent on the trophoblast-decidual interaction and on an adequate blood supply to the implantation sites. Nitric oxide (NO) has been shown to play an important role during advanced gestation, although its role during early pregnancy is unclear. The aim of the present study in rats was to evaluate whether NO plays a role during the preimplantation [days 1-4 post coitum (p.c.)] and peri-implantation (days 6-8 p.c.) phases of pregnancy. The rats were treated with the non-specific nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine methyl ester (L-NAME), and the iNOS inhibitor aminoguanidine in the presence and absence of low-dose antiprogestin, onapristone, and evaluated on days 9 p.c. and 19 p.c., respectively. Before implantation, the treatments alone (L-NAME, aminoguanidine, onapristone) had little effect on pregnancy outcome. Conversely, aminoguanidine plus onapristone treatment completely prevented pregnancy, whereas L-NAME plus onapristone reduced the pregnancy rate to approximately 50%. In addition, both treatments drastically reduced decidualization. Oviductal flushing experiments revealed arrest of embryo development at around the 8-cell stage after aminoguanidine plus onapristone treatment on days 1-4 p.c. Similarly, treatment during the peri-implantation period with L-NAME, aminoguanidine, and onapristone each had only marginal effects on pregnancy. However, a combination of L-NAME and onapristone, and aminoguanidine plus onapristone prevented pregnancy in 71% and 42% of dams, respectively, as determined on day 19 p.c. These treatments also markedly inhibited the decidualization process. This study demonstrates synergistic effects of NOS inhibitors and an antiprogestin in preventing pregnancy. NOS, particularly the cytokine- and progesterone-inducible iNOS, may represent a new target for novel therapeutic agents capable of promoting or inhibiting pregnancy.

Nitric oxide modulates placental prostanoid production from late pregnant non-insulin-dependent diabetic rat

Severe reproductive dysfunction has been described in non-insulin-dependent diabetes mellitus (NIDDM), correlated with high glucose levels in the plasma. We have characterized an abnormal prostanoid profile in tissues from NIDDM rats, and a tight correlation between nitric oxide (NO) levels and prostaglandin production. Likewise, we have determined that parturition is delayed in NIDDM rats compared to control animals. In order to characterize the events which precede delayed parturition in NIDDM rats, we evaluate (a) the arachidonic acid (AA) conversion in placental tissue obtained from control (day 21 and 22) and NIDDM (day 21, 22 and 23) late pregnant rats into prostaglandin E2 (PGE2) and F2alpha (PGF2alpha), thromboxane B2 (TXB2) and 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha), and (b) NO synthase (NOS) activity in control and NIDDM late pregnant animals. Placental arachidonate conversion from control rats into different prostanoids, namely PGE2, PGF2alpha, and TXB2, is higher in day 22 than in day 21, and radioconversion from diabetic rats into PGE2, PGF22, TXB2 and 6-keto-PGF1alpha on day 23 is higher than in day 21 and 22. 6-keto-PGF1alpha is lower and TXB2 is higher in diabetic tissues than in control. Placental AA conversion of control diabetic tissues on the day of delivery is decreased by N(G) monomethyl-L-arginine (LNMMA) (600 mM), a well known NOS inhibitor, while prostanoid production remains unaltered on previous days. NOS activity is higher in control on day 22 when compared to day 21, and in diabetic on day 23 when compared to day 22 of pregnancy. We conclude that elevated NO placental levels are observed in control (day 22) and NIDDM (day 23) rats, and may increase placental prostaglandin production on the day of delivery.