Role of nitric oxide in the biology, physiology and pathophysiology of reproduction

The concentration of nitrite in seminal plasma does not correlate with sperm concentration, sperm motility, leukocytospermia, or sperm culture

OBJECTIVE

To correlate the concentration of nitrite (the stable metabolite of nitric oxide) in seminal plasma with sperm number and motility, leukocytospermia, and sperm culture.

DESIGN

Prospective study.

SETTING

Academic research institution.

PATIENT(S)

Seventy normozoospermic or dyspermic men enrolled in an artificial insemination/in vitro fertilization program.

INTERVENTION(S)

Semen samples (n = 70) were checked for sperm concentration, total sperm count, sperm motility, seminal leukocyte concentration, and sperm culture; similarly, the concentration of nitrite in seminal plasma was measured by Griess reaction.

MAIN OUTCOME MEASURE(S)

Measurement of nitrite concentration in seminal plasma and its correlation with sperm concentration, total sperm count, sperm motility, leukocytospermia, and sperm culture.

RESULT(S)

The concentration of nitrite in seminal plasma does not correlate with sperm concentration, total sperm count, or with the proportion of immotile or rapid-forward motile spermatozoa. Moreover, the concentration of nitrite in seminal plasma is not significantly increased when sperm culture is positive, nor does it correlate with leukocyte concentration in semen.

CONCLUSION(S)

Our results do not support the hypothesis that in vivo nitric oxide synthesis affects sperm function; alternatively, our results could suggest that nitrite in the seminal plasma is not a sensitive marker of in vivo nitric oxide synthesis.

Erection and NO override the vasoconstrictive effect of alpha-adrenergic stimulation in the rat penile vasculature

Studies in this laboratory are designed to determine the effects of vasoconstrictor agents on the erectile response in rats. We have previously demonstrated that the vasoconstrictor effect of endothelin-1 (ET-1) is sharply reduced by erection and by nitric oxide (NO) administration. The present study was performed to determine if vasoconstriction, resulting from alpha-adrenergic stimulation, is altered by erection and NO. During continuous monitoring of corpus cavernosum pressure (CCP) and mean arterial pressure (MAP), erection was induced by electrical stimulation of the autonomic ganglion for the innervation of the penis. When the alpha-adrenergic agonist methoxamine (METH, 10 microg/kg) was injected before erection (ie, into the non-erect penis), the subsequent erectile response (CCP/MAP) was significantly reduced from 0.68+/-0.03 before METH to 0.34+/-0.08 after METH. Injection of METH into the erect penis (ie, during erection) reduced the vasoconstrictor action of METH; CCP/MAP was 0.74+/-0.02 before METH and 0.55+/-0.05 after METH (P<0.05). The vasoconstrictor action of METH was slightly reduced when given in conjunction with NOR-1, a NO donor drug; CCP/MAP was 0.70+/-0.05 before METH, 0.55+/-0.09 after METH but this change was not significant. These results demonstrate that the response to alpha-adrenergic stimulation is attenuated during erection in response to ganglionic stimulation. Furthermore, it appears that NO, produced during erection, may serve to override agonist-induced vasoconstriction. These results support our hypothesis that NO acts to directly stimulate relaxation of cavernous smooth muscle and to inhibit the vasoconstrictor actions of agents like ET-1 and alpha-adrenergic agonists including norepinephrine.

Signaling Pathway of Nitric Oxide-Induced Acrosome Reaction in Human Spermatozoa1

Nitric oxide (NO) has been recently shown to modulate in vitro motility, viability, the acrosome reaction (AR), and metabolism of spermatozoa in various mammalian species, but the mechanism or mechanisms through which it influences sperm functions has not been clarified. In human capacitated spermatozoa, both the intracellular cGMP level and the percentage of AR-positive cells were significantly increased after 4 h of incubation with the NO donor, sodium nitroprusside (SNP). SNP-induced AR was significantly reduced in the presence of the soluble guanylate cyclase (sGC) inhibitors, LY83583 and ODQ; this block was bypassed by adding 8-bromo-cGMP, a cell-permeating cGMP analogue, to the incubation medium. Finally, Rp-8-Br-cGMPS and Rp-8-pCPT-cGMPS, two inhibitors of the cGMP-dependent protein kinases (PKGs), inhibited the SNP-induced AR. Furthermore, SNP-induced AR did not occur in Ca2+ -free medium or in the presence of the protein kinase C (PKC) inhibitor, calphostin C. This study suggests that the AR-inducing effect of exogenous NO on capacitated human spermatozoa is accomplished via stimulation of an NO-sensitive sGC, cGMP synthesis, and PKG activation. In this effect the activation of PKC is also involved, and the presence of extracellular Ca2+ is required.

Nitric oxide as a regulator in preimplantation embryo development and apoptosis

OBJECTIVE

To investigate the mechanisms of nitric oxide (NO) in the development and apoptosis of preimplantation mouse embryos.

DESIGN

Prospective, controlled study.

SETTING

Medical college laboratory.

SUBJECT(S)

Two-cell embryos from outbred ICR mice.

INTERVENTION(S)

Hyperstimulation protocol, two-cell embryos were collected, then treated with or without an NO synthase inhibitor (L-NAME) or an NO donor (SNP) and combined with a cGMP analogue (8-Br-cGMP) or a selective inhibitor of NO-sensitive soluble guanylyl cyclase (ODQ).

MAIN OUTCOME MEASURE(S)

The development of ICR mouse embryo from two cells to blastocyst stages in vitro.

RESULT(S)

The development of blastocyst was inhibited by L-NAME in a concentration-dependent manner (0.1-10 microM) and 0.1 microM SNP reversed this effect (80.5% of control). Annexin-V/propidium iodide and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling techniques demonstrated that excessive NO (> or =10 microM) might induce apoptosis in the mouse embryos. 8-Br-cGMP reversed the inhibitory effect of L-NAME and rescued the embryo growth. ODQ inhibited the embryo development in a dose-responsive fashion (0.1--100 microM) but had no effect in the NO-induced embryo apoptosis. P53 and Bax were found to be up-regulated during the embryo fragmentation.

CONCLUSION(S)

These results indicate that the cGMP pathway might be involved in the NO-regulated embryonic development, but not in NO-induced apoptosis, for which P53/Bax pathway might be involved.

Nitric oxide synthase expression and nitric oxide/cyclic GMP pathway in swine granulosa cells

The present investigation was undertaken to verify if the two nitric oxide synthase isoforms, eNOS and iNOS, are present in swine granulosa cells and whether the enzyme soluble guanylate cyclase is functionally active in the same cells and can account for NO effects. Using western blotting, the presence of endothelial NO synthase was demonstrated in freshly collected cells; on the contrary, iNOS expression was not observed in the same cells either before or after culture with the inflammatory cytokine hTNF-alpha. The treatment with a strong NO donor (S-Nitroso-L-acetyl penicillamine, SNAP) determined an increase of cGMP levels in culture media, which was attenuated by the combined treatment with an inhibitor of NO-sensitive soluble guanylate cyclase, 1H-[1,2,3]oxadiaziolo [4,3a]quinoxaline -1-one (ODQ). The cGMP analog, 8 bromo-cGMP, mimicked the strong inhibitory effect exerted by SNAP on estradiol 17 beta and progesterone production, while ODQ did not modify steroids concentrations in culture media. These observations demonstrate the presence of a follicular NO-generating system, which in swine granulosa cells seems to include only the endothelial NOS isoform. Furthermore, the nitric oxide/cyclic GMP system seems to be functionally active in these cells, since cGMP appears to mediate NO action, even if it cannot account completely for NO inhibitory effect on steroidogenesis.

Perinatal development of endothelial nitric oxide synthase-deficient mice

The purpose of this study was to evaluate the influence of endothelial nitric oxide synthase (eNOS) deficiency on fetal growth, perinatal survival, and limb development in a mouse model with a targeted mutagenesis of the Nos3 gene. Wild-type (Nos3+/+) and eNOS-deficient fetuses (Nos3-/-) were evaluated on Gestational Day (E)15 and E17, and newborn pups were observed on Day 1 of life (D1). The average term duration of pregnancy was 19 days. For the evaluation of postnatal development, a breeding scheme consisting of Nos3+/- x Nos3+/- and Nos3-/- x Nos3-/- mice was established, and offspring were observed for 3 wk. Southern blotting was used for genotyping. No significant differences in fetal weight, crown-rump lengths (CRL), and placental weight were seen between Nos3+/+ and Nos3-/- fetuses on E15. By E17, Nos3-/- fetuses showed significantly reduced fetal weights, CRL, and placental weights. This difference in body weight was also seen throughout the whole postnatal period. In pregnancies of Nos3-/- females, the average number of pups alive on D1 was significantly decreased compared to either E15 or E17. Placental histology revealed no abnormalities. On E15, E17, and D1, Nos3(-/-) fetuses demonstrated focal acute hemorrhages in the distal limbs in 0%, 2.6%, and 5.7%, respectively, of all mutant mice studied on the respective days. Bone measurements showed significantly shorter bones in the peripheral digits of hindpaws of Nos3-/- newborns. We conclude mice deficient for eNOS show characteristically abnormal prenatal and postnatal development including fetal growth restriction, reduced survival, and an increased rate of limb abnormalities. The development of this characteristic phenotype of eNOS-deficient mice dates back to the prenatal development during the late third trimester of pregnancy.

Nitric oxide production is increased in the spermatic veins of adolescents with left idiophatic varicocele

BACKGROUND/PURPOSE

The existence of an excessive release of nitric oxide (NO) within dilated spermatic veins has been recorded in adults with varicocele suggesting a high oxidative stress. The authors investigated whether NO overproduction is already present in the dilated veins of adolescent varicocele and which enzymatic isoforms in the spermatic vein could be expressed.

METHODS

The study group consisted of 10 adolescent patients affected by left idiophatic varicocele of grade II and III. The increase in NO production was established by determination of serum concentration of L-hydroxyarginine (L-NHA) and Nitrite/nitrate (NOx). Both endothelial and inducible NOsynthase (NOS) were investigated by Western blot analysis and by immunohistochemical localization using specific monoclonal fluorescein conjugated antibodies.

RESULTS

Serum L-NHA levels were significantly greater in the spermatic veins when compared with the peripheral veins 176.8 +/- 32.3 micromol/L versus 3.38 +/- 0.64 micromol/L (P =.0004 Similarly, NOx levels were increased, respectively, 68.2 +/- 16.7 nmol/mL versus 12.9 +/- 2.65 nmol/mL (P =.029). Endothelial NOS was localized in the spermatic vein of varicocele patients, but not overexpressed; the inducible isoform was not detected.

CONCLUSIONS

Adolescents with varicocele already present an increase in NO within dilated veins. The dilated spermatic vein is not the major source for the increase in NO level. These results could have an implication in the natural history of adolescent varicocele and in programming the ideal time for surgical treatment.

Innervation of NADPH diaphorase-containing neurons correlated with acetylcholinesterase, tyrosine hydroxylase, and neuropeptides in the pigeon cloaca

The motility of the avian cloaca is under neural control, but little is known about the neural network that accomplishes this function. This present study was designed to determine the distribution of nitric oxide-synthesising neurons in the pigeon cloaca by enzyme histochemistry for reduced nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d). NADPH-d-positive staining was seen in the neurons and fibres in the cloaca. The highest density of nerve fibres was noted in the coprodeum and the lowest in the proctodeum. In the coprodeum, NADPH-d neurons were found singly, formed small groups of 2-10 neurons, or were seen in plexuses in the muscle layer, lamina propria, or around the arterioles. Several NADPH-d-positive neurons were also observed in the ganglia of the cloaca. NADPH-d fibres ran in the muscle layer, lamina muscularis mucosae and lamina propria, or surrounded blood vessels. The distribution pattern of acetylcholinesterase (AChE)-stained neurons and fibres in the cloaca was similar to that of NADPH-d. Double staining for NADPH-d and AChE showed colocalisation of the 2 enzymes in many neurons of the cloaca. Tyrosine hydroxylase (TH)-immunoreactive nerve fibres originating outside the cloaca were also noted. In the urodeum and proctodeum, neurons or fibres positive for NADPH-d, AChE or TH were scattered in the lamina propria. Nerve fibres immunoreactive for calcitonin-gene related peptide, galanin, methionine-enkephalin, substance P, and vasoactive intestinal peptide were found sparsely in the cloaca. Our results demonstrate that nitrergic neurons constitute a subpopulation which is closely associated with the cholinergic system in the pigeon cloaca.

Antagonism of Rho-kinase stimulates rat penile erection via a nitric oxide-independent pathway

Relaxation of the smooth muscle cells in the cavernosal arterioles and sinuses results in increased blood flow into the penis, raising corpus cavernosum pressure to culminate in penile erection. Nitric oxide, released from non-adrenergic/non-cholinergic nerves, is considered the principle stimulator of cavernosal smooth muscle relaxation, however, the inhibition of vasoconstrictors (that is, norepinephrine and endothelin-1, refs. 5-9) cannot be ignored as a potential regulator of penile erection. The calcium-sensitizing rho-A/Rho-kinase pathway may play a synergistic role in cavernosal vasoconstriction to maintain penile flaccidity. Rho-kinase is known to inhibit myosin light chain phosphatase, and to directly phosphorylate myosin light-chain (in solution), altogether resulting in a net increase in activated myosin and the promotion of cellular contraction. Although Rho-kinase protein and mRNA have been detected in cavernosal tissue, the role of Rho-kinase in the regulation of cavernosal tone is unknown. Using pharmacologic antagonism (Y-27632, ref. 13, 18), we examined the role of Rho-kinase in cavernosal tone, based on the hypothesis that antagonism of Rho-kinase results in increased corpus cavernosum pressure, initiating the erectile response independently of nitric oxide. Our finding, that Rho-kinase antagonism stimulates rat penile erection independently of nitric oxide, introduces a potential alternate avenue for the treatment of erectile dysfunction.

Factors controlling ovarian apoptosis

Apoptosis is a form of programmed cell death that is essential for the development of the embryo and adult tissue plasticity. In adults, it is observed mainly in those tissues undergoing active differentiation such as the hematopoietic system, testis, ovary, and intestinal epithelium. Apoptosis can be triggered by many factors, such as hormones, cytokines, and drugs, depending on the type of the cell. While the intracellular signaling mechanisms may vary in different cells, they all display similar morphological and biochemical features at the later stages of the apoptotic process. This review focuses on the factors controlling ovarian apoptosis, emphasizing observations made on GnRH-induced apoptotic process in goldfish follicles.Key words: apoptosis, ovary, GnRH.

Influence of nitric oxide and noradrenaline on prostaglandin F(2)(alpha)-induced oxytocin secretion and intracellular calcium mobilization in cultured bovine luteal cells

Although prostaglandin (PG) F(2alpha) released from the uterus has been shown to cause regression of the bovine corpus luteum (CL), the neuroendocrine, paracrine, and autocrine mechanisms regulating luteolysis and PGF(2alpha) action in the CL are not fully understood. A number of substances produced locally in the CL may be involved in maintaining the equilibrium between luteal development and its regression. The present study was carried out to determine whether noradrenaline (NA) and nitric oxide (NO) regulate the sensitivity of the bovine CL to PGF(2alpha) in vitro and modulate a positive feedback cascade between PGF(2alpha) and luteal oxytocin (OT) in cows. Bovine luteal cells (Days 8-12 of the estrous cycle) cultured in glass tubes were pre-exposed to NA (10(-5) M) or an NO donor (S-nitroso-N:-acetylpenicillamine [S-NAP]; 10(-4) M) before stimulation with PGF(2alpha) (10(-6) M). Noradrenaline significantly stimulated the release of progesterone (P(4)), OT, PGF(2alpha), and PGE(2) (P: < 0.01); however, S-NAP inhibited P(4) and OT secretion (P: < 0.05). Oxytocin secretion and the intracellular level of free Ca(2+) ([Ca(2+)](i)) were measured as indicators of CL sensitivity to PGF(2alpha). Prostaglandin F(2alpha) increased both the amount of OT secretion and [Ca(2+)](i) by approximately two times the amount before (both P: < 0.05). The S-NAP amplified the effect of PGF(2alpha) on [Ca(2+)](i) and OT secretion (both P: < 0.001), whereas NA diminished the stimulatory effects of PGF(2alpha) on [Ca(2+)](i) (P: < 0.05). Moreover, PGF(2alpha) did not exert any additionally effects on OT secretion in NA-pretreated cells. The overall results suggest that adrenergic and nitrergic agents play opposite roles in the regulation of bovine CL function. While NA stimulates P(4) and OT secretion, NO may inhibit it in bovine CL. Both NA and NO are likely to stimulate the synthesis of luteal PGs and to modulate the action of PGF(2alpha). Noradrenaline may be the factor that is responsible for the limited action of PGF(2alpha) on CL and may be involved in the protection of the CL against premature luteolysis. In contrast, NO augments PGF(2alpha) action on CL and it may be involved in the course of luteolysis.

Nitric oxide dysfunction in the pathophysiology of preeclampsia

Researchers disagree as to the importance of nitric oxide (NO) in preeclampsia. Many researchers have alluded to NO's possible primary or secondary role in the development of preeclampsia, but few have correlated the dysfunction of nitric oxide production with the other metabolic derangements seen in this condition. This paper will review the evidence that the primary dysfunction in preeclampsia is a relative deficiency of available NO (secondary to oxidative degradation) and an excess of peroxynitrite (ONOO(-)). The combination of a deficiency of NO and an increase in ONOO(-) can directly or indirectly initiate the vast majority of physiological and serological changes associated with preeclampsia, such as blood pressure, increased glomerular filtration rate, proteinuria, platelet dysfunction, increased thromboxane and endothelin, and a decrease in prostacyclin. Understanding the complex role of nitric oxide in this condition may explain why previous interventions have been unsuccessful and suggest possible strategies for prevention and treatment in the future.

Follicular fluid concentrations of adrenomedullin, vascular endothelial growth factor and nitric oxide in IVF cycles: relationship to ovarian response

Marked granulosa cell proliferation along with important changes in the vascular bed of the ovary characterize IVF cycles associated with multiple follicular growth and maturation. The present report investigated follicular fluid (FF) and circulating concentrations of adrenomedullin, vascular endothelial growth factor (VEGF) and nitric oxide (NO) in 70 IVF patients (14 of whom became pregnant); these three vasoactive substances may be implicated in extensive ovarian tissue remodelling. Serum and FF concentrations of oestradiol and progesterone were also measured in the 70 IVF cycles studied. Follicular fluid concentrations of VEGF and adrenomedullin but not nitrite/nitrate (the two stable oxidation products of NO metabolism) were significantly higher (P < 0.0001) than the corresponding circulating concentrations. Follicular fluid concentrations of oestradiol and progesterone were not correlated with those of adrenomedullin, VEGF or nitrite/nitrate. No relationship existed between circulating concentrations of adrenomedullin, VEGF or nitrite/nitrate on the day of oocyte aspiration and parameters of ovarian response to gonadotrophin stimulation. In contrast, FF adrenomedullin concentration showed a direct relationship with day 3 FSH serum concentration (r = 0.53, P < 0.01) and the number of ampoules of gonadotrophin administered (r = 0.36, P < 0.005), but an inverse correlation with the total number of oocytes retrieved (r = -0.29, P < 0.01) and the number of mature oocytes (r = -0.25, P < 0. 05). A positive correlation was found for FF VEGF concentration and chronological age (r = 0.29, P < 0.05) and ampoules of gonadotrophins administered (r = 0.30, P < 0.05). There was no relationship between nitrite/nitrate FF concentrations and parameters of ovarian response. Neither serum concentrations nor FF concentrations of adrenomedullin, VEGF or nitrite/nitrate were correlated with IVF outcome. This study suggested for the first time that increased FF concentrations of adrenomedullin can be a marker of decreased ovarian response in IVF. Our results also provide further evidence favouring an association between FF VEGF and patient's age, while on the basis of our findings NO measurements are not a useful marker of ovarian response.

Distribution of NADPH-diaphorase and nitric oxide synthase (NOS) in different regions of porcine oviduct during the estrous cycle

Nitric oxide synthase (NOS) is responsible for the biological production of nitric oxide (NO) in several organs, including those of the reproductive tract. We investigated potential changes in NADPH-diaphorase (NADPH-d) activity (marker for NOS activity) and the presence and distribution of NOS in the porcine oviduct. Tissues were obtained from gilts (n=16) on different days of the estrous cycle. One fallopian tube was used for histo- and immunohistochemistry and the other for Western blotting analysis. NADPH-d activity was much higher in the epithelium of the mucosa than in the myosalpinx. The highest activity of NADPH-d was always found in the epithelium of the isthmus. The intensity of the reaction (arbitrary units +/- SEM) in isthmus epithelium increased from the postovulatory period until early proestrus (96.2 +/- 11.2) and then gradually decreased. The lowest intensity of NADPH-d reaction in the epithelium of the isthmus was seen at estrus (58.4 +/- 7.7). The most intense NADPH-d activity in myosalpinx of all parts of the oviduct was observed at the postovulatory stage of the estrous cycle (isthmus 38.3 +/- 2.5; ampulla 35.6 +/- 4.2; infundibulum 24.7 +/- 0.8) and then decreased during the remaining stages of the estrous cycle (p< 0.001). The presence of endothelial NOS (eNOS) was detected in epithelial cells of mucosa and in endothelium of vascular tissues and myosalpinx during all studied days of the estrous cycle. The positive reaction for inducible NOS (iNOS) was restricted only to the endothelium of lymph vessels and some blood vessels. Because our Western blotting analysis revealed that porcine oviduct contains eNOS but not iNOS, we suggest that eNOS is the main isoform of NOS expressed in the porcine oviduct. We concluded that the different activity of NADPH-d in the various regions of the oviduct, accompanied by changes in its activity during the course of the estrous cycle, could indicate an important role of NO in regulation of tubal function.

Production of prostaglandin f(2alpha) by cultured bovine endometrial cells in response to tumor necrosis factor alpha: cell type specificity and intracellular mechanisms

Tumor necrosis factor alpha (TNFalpha) has been shown to be a potent stimulator of prostaglandin (PG) F(2alpha) secretion in the bovine endometrium. The aims of the present study were to determine the cell types in the endometrium (epithelial or stromal cells) responsible for the secretion of PGF(2alpha) in response to TNFalpha, and the intracellular mechanisms of TNFalpha action. Cultured bovine epithelial and stromal cells were exposed to TNFalpha (0.006-6 nM) or oxytocin (100 nM) for 4 h. TNFalpha resulted in a dose-dependent increase of PGF(2alpha) production in the stromal cells (P < 0.001) but not in the epithelial cells. On the other hand, oxytocin stimulated PGF(2alpha) output in the epithelial cells but not in the stromal cells. When the stromal cells were incubated for 24 h with TNFalpha and inhibitors of phospholipase (PL) C or PLA(2), only PLA(2) inhibitor completely stopped the actions of TNFalpha (P < 0.001). When the stromal cells were exposed to TNFalpha and arachidonic acid, the action of TNFalpha was augmented (P < 0.001). When the stromal cells were incubated for 24 h with a nitric oxide (NO) donor (S-NAP), S-NAP stimulated the PGF(2alpha) production dose-dependently. Although an NO synthase (NOS) inhibitor (L-NAME) reduced TNFalpha-stimulated PGF(2alpha) production, an inhibitor of phosphodiesterase augmented the actions of TNFalpha and S-NAP (P < 0. 05). The overall results indicate that the target of TNFalpha for stimulation of PGF(2alpha) production in cattle is the endometrial stromal cells, and that the actions of TNFalpha are mediated via the activation of PLA(2) and arachidonic acid conversion. Moreover, TNFalpha may exert a stimulatory effect on PGF(2alpha) production via the induction of NOS and the subsequent NO-cGMP formation.

Nitric oxide inhibits prostanoid synthesis in the rat oviduct

We have studied the effect of nitric oxide (NO) on the production of arachidonic acid ([14C]-AA) metabolites in the rat oviduct. The basal synthesis of eicosanoids was measured by the conversion of ([14C]-AA) to the different radiolabeled products of cyclooxygenase (COX). The oviducts incubated for 1 h with the labeled substrate of COX were able to convert 3.3 +/- 0.3% of ([14C]-AA) to 6-ceto-PGF1alpha, 10.7 +/- 1.0% to PGF2alpha, 13.5 +/- 1.2% to PGE2 and 6.3 +/- 0.5% to TXB2. The tissues were incubated with different doses of two NO donors: SIN-1 and Spermine NONOate. The results indicated that SIN-1 produces a significant decrease (50%; P < 0.05) in all prostanoids evaluated in a dose-response fashion. The inhibitory effect was completely reversed by addition of 20 microg/ml of hemoglobin (Hb), a NO scavenger. The addition of Spermine NONOate to the incubation medium diminished significantly (65%) the synthesis of COX metabolites suggesting that NO acts by inhibiting COX activity in the rat oviduct. However, NOS inhibitors, N(G)-L-arginine-methyl-ester (L-NAME) nd N(G)-L-monomethyl-arginine (L-NMMA) had no effect on basal production of the prostanoids. These results indicate that in the rat oviduct the synthesis of COX metabolites is negatively regulated by nitric oxide.

Relationships between concentrations of tumor necrosis factor-alpha and nitric oxide in follicular fluid and oocyte quality

PURPOSE

Our objective was to explain a relationship between concentrations of tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO) in follicular fluid, oocyte quality, and outcomes of in vitro fertilization--embryo transfer (IVF-ET).

METHODS

The concentrations of TNF-alpha and NO were measured in 115 follicular fluid samples collected from 43 patients undergoing IVF-ET program, due to tubal obstruction, some with endometriosis (8 patients) or hydrosalpinx (5 patients). A correlation of these factors concentrations and the oocyte quality, the oocyte maturity, and infertility-associated diseases was analyzed.

RESULTS

No correlation was found between concentrations of NO and TNF-alpha in follicular fluid. NO concentrations in follicular fluids were significantly higher in patients with endometriosis (P < 0.001) or hydrosalpinx (P < 0.01) compared to the patients with just tubal obstruction. Follicular NO concentration differences according to oocyte maturity and oocyte quality were not found. In contrast, TNF-alpha concentrations in follicular fluids were significantly higher in poor quality oocytes (P < 0.05) but were not associated with infertility-associated diseases, such as hydrosalphinx or endometriosis,and the oocyte maturity. No significant differences in follicular levels of NO and TNF-alpha as well as IVF-ET parameters of pregnant and nonpregnant groups were revealed.

CONCLUSIONS

There is no significant correlation between the concentrations of NO and TNF-alpha in follicular fluid. NO levels in follicular fluid are altered in infertility-associated diseases. However, TNF-alpha levels but not NO levels influence oocyte quality. These results suggest that the production of NO and TNF-alpha in follicular fluid may be regulated via different pathways and can be tempered with infertility-associated diseases, thereby influencing oocyte quality locally.

Different actions of noradrenaline and nitric oxide on the output of prostaglandins and progesterone in cultured bovine luteal cells

The effects of noradrenaline (NA) and nitric oxide (NO) on prostaglandins (PGs) and progesterone (P4) secretion during the development of the bovine corpus luteum (CL) were investigated. Bovine luteal cells of early and mid-cycle CL were cultured for 20 to 24 h in medium containing 10% calf serum, washed, and treated with NA or nitrergic agents for an additional 16 h in a serum-free medium. NA (10(-5) M) stimulated P4 from early and mid-cycle CL by 238% and 154% (P < 0.01), respectively. Moreover, although NA induced a twofold increase in PGE2 secretion (P < 0.01) in both examined periods, the effect of NA on PGF2alpha secretion was approximately 1.5 times higher (P < 0.05) in early than in mid-cycle CL. Two NO synthase inhibitors, L-NAME and L-NOARG (both 10(-4) M), stimulated P4 secretion only in mid-luteal cells (P < 0.01), although they did not affect the cells from early CL. Although a NO donor, S-NAP (10(-4) M) inhibited P4 secretion from mid-cycle luteal cells (P < 0.05), it strongly stimulated PGE2 in both examined phases (P < 0.001). On the other hand, the output of PGF2alpha was stimulated by S-NAP only in the cells of the mid-cycle CL (P < 0.01). The overall results suggest that adrenergic and nitrergic agents play opposite roles in the regulation of bovine CL functions. Whereas NA may play a supporting role in luteal development, NO may participate in the functional regression of the bovine CL by inhibiting steroidogenesis.

Arginine nutrition in development, health and disease

As a precursor of nitric oxide, polyamines and other molecules with enormous biologic importance, L-arginine plays versatile key roles in nutrition and metabolism. Arginine is an essential amino acid in the fetus and neonate, and is conditionally an essential nutrient for adults, particularly in certain disease conditions. L-Arginine administration is beneficial in improving reproductive, cardiovascular, pulmonary, renal, gastrointestinal, liver and immune functions, and in facilitating wound healing. The effect of L-arginine in treating many common health problems is unique among amino acids, and offers great promise for improved health and well-being in the future.

Selenium stimulates estradiol production in bovine granulosa cells: possible involvement of nitric oxide

Reduction in fertility is well known to be possibly related to selenium deficiencies, even if target organ for selenium action is, at present, unclear. The present study was aimed to examine whether selenium directly influences granulosa cells. Bovine granulosa cells from different size follicles were used to investigate the effect of selenium (5 ng/ml), with or without bovine follicle-stimulating hormone (bFSH) (100 ng/ml), on proliferation and steroidogenesis. In addition, we sought to determine if selenium modulates the production of nitric oxide, which is known to play an important role in ovarian activity. Our data demonstrate that selenium significantly (P < 0.001) stimulates the proliferation of the cells from small follicles; moreover, it further potentiates the stimulatory effect of the gonadotropin in the same cells. Furthermore, selenium significantly (P < 0.01) augments E2 output by cells from both kinds of follicles. bFSH increases E2 production (P < 0.01) by cells from large follicles, whereas it exerts a stimulatory (P < 0.01) effect only in the presence of selenium in the cells from the small ones. The production of nitric oxide is significantly increased (P < 0.001) by bFSH, but only in cells from small follicles. Selenium inhibits (P < 0.001) nitric oxide production in cells from both kinds of follicles and significantly decreases (P < 0.001) bFSH-induced nitric oxide production in cells from the small ones. We conclude that selenium acts on granulosa cells by modulating their proliferation and E2 synthesis; moreover, its effect could be mediated, at least in part, through an inhibition of nitric oxide.

The effect of nitric oxide on sperm cell function and embryo development

PROBLEM

Nitric oxide (NO) has been known to have multifunctional roles both in the male and female reproductive systems. We investigated the effects of sodium nitroprusside (SNP)-dependent NO release on sperm cell function and embryo development to elucidate the mechanisms of action of NO.

METHOD OF STUDY

Semen samples from 20 healthy men were processed by the swim-up method. Sperm motility, hyperactivation, and acrosome reaction were examined following incubation with various concentrations of SNP. The concentration of 10 nM to 1 mM was used for sperm motility and hyperactivation measurement and 1 microM to 1 mM for examining the effect on acrosome reaction. Embryo development to blastocyst stage was assessed using 100 nM to 1 mM of SNP added before transferring the mouse embryos into the culture medium. Finally, to understand the mechanism of action of NO, changes in embryo development were examined after zygotes were treated with various concentrations ranging up to 1 mM of 8-bromo-cGMP, an analog of cGMP.

RESULTS

Both sperm motility and hyperactivation were significantly reduced at 100 microM and 1 mM concentrations of SNP after 6 hr of incubation. After 24 hr of incubation, they were greatly decreased with all, except the 10 nM concentration of SNP. The percentage of acrosomal-reacted spermatozoa was increased with the increasing concentration of SNP following incubation with 10 microM and 1 mM of SNP. Embryo development was arrested since the two-cell embryonic stage with all except the 100 nM concentration of SNP, and inhibited by 200 microM of SNP regardless of SNP treatment stage. However, embryo development was not influenced by 8-bromo-cGMP.

CONCLUSIONS

We concluded that SNP-inhibited sperm cell function and embryo development in a dose- and time-dependent manner, and the inhibitory effect on embryo development, may not be a stage-specific treatment mediated via a cGMP-independent pathway. This result suggests that NO may be enough to affect the fecundity potential in vivo.

Effects of a nitric oxide donor and nitric oxide synthase inhibitors on luteinizing hormone-induced ovulation in the ex-vivo perfused rat ovary

The aim of this study was to investigate the role of nitric oxide (NO) in ovulation and ovarian steroidogenesis by the use of NO synthase (NOS) inhibitors and an NO donor administrated to the luteinizing hormone (LH)-stimulated ex-vivo perfused pre-ovulatory rat ovary. The ovaries were stimulated with LH (0.2 microgram/ml) alone or in combination with the phosphodiesterase inhibitor IBMX (200 micromol/l). The presence of both endothelial NOS (eNOS) and inducible NOS (iNOS) in the perfused rat ovary were detected by immunoblotting and a clear increase in amount of iNOS protein was seen after LH+IBMX stimulation. The addition of a non-selective NOS inhibitor, N(G)-monomethyl-L-arginine (L-NMMA; 300 micromol/l), to the perfusate significantly decreased ovulation numbers (median = 4. 0, range = 1-14) as compared with LH + IBMX stimulated control (12.0, 6-17). In contrast, an inhibitor with relative selectivity towards iNOS, aminoguanidine bicarbonate (AG, 300 micromol/l and 1 mmol/l), did not change the ovulation rate (11.5, 6-18 and 11.0, 7-15 respectively). In perfusions with only LH, a lower ovulation rate was seen but with similar effects (0.0, 0-8 for L-NMMA; 7.5, 3-12 for control and 7.0, 1-15 for AG 300 micromol/l). The administration of an NO donor, spermine NONOate, resulted in similar ovulation numbers as in LH-stimulated controls. The NO inhibitors did not affect steroid concentrations in the perfusion media, while 100 micromol/l NONOate increased progesterone production.

Gender and pregnancy affect neuropeptide responses of the rabbit Achilles tendon

Tendons such as the Achilles tendon are complex structures that are hypocellular, hypovascular, and hyponeural. The development of pathophysiologic function in this tendon because of overuse is relatively common; however, the mechanisms responsible for the development of paratenonitis and tendinosis remain primarily undefined. To understand better a possible regulatory role for neuropeptides (substance P and calcitonin gene related peptide) known to be present in this tissue, the influence of substance P and calcitonin gene related peptide on messenger ribonucleic acid levels for numerous inflammatory molecules, growth factors, and proteinases and inhibitors have been assessed using a semiquantitative reverse transcription-polymerase chain reaction method and explants of paratenon and Achilles tendon midsubstance tissue from adolescent male and female rabbits and tissue from primigravida females. Most of the significant (p < 0.01) changes observed were at the level of the growth factor transcripts and transcripts for proteinases and inhibitors. Twenty-one significant differences in the responsiveness between tissues from male and female rabbits were observed, and 12 significant differences in responsiveness between virgin females and primigravida rabbits were seen. Differences between paratenon and midsubstance responsiveness to the neuropeptides also were observed within each group of animals. The midsubstance tissue from pregnant animals was hyporesponsive to both neuropeptides. These results indicate that neurotransmitter responsiveness of Achilles tendon tissue differs in a gender specific manner and is influenced by pregnancy associated factors.