The relationship between varicocele and semen nitric oxide concentrations

Thymoquinone improves testicular damage and sperm quality in experimentally varicocele-induced adolescent rats

The aim of this study was to investigate the protective and therapeutic effects of thymoquinone against the negative effects of varicocele on testicular tissue and sperm morphology. Five groups were formed by random selection from a total of 40 adult male Wistar rats (n = 8). Thymoquinone (5 mg/kg/day) was administered intraperitoneally to the varicocele-dimethyl sulfoxide-olive oil-thymoquinone (VT) group and the sham-thymoquinone group. At the end of the 60th day, all groups were anaesthetised and the left testis was removed from the body quickly. One half of the testis tissue, which was divided into two, was separated for biochemical and Western blot analysis, while the other half were fixed in Bouin's fixative. As a result of biochemical, molecular and histopathological analyses, a statistically significant increase was found in the varicocele group testicular tissues in the malondialdehyde level, apoptotic index, Bax expression, cytochrome c expression and Bax/Bcl-2 ratio compared with the sham group. In addition, histopathological changes characterised by partial or complete degeneration of the germinal epithelium were observed in the seminiferous tubules in the same group. Total oxidant status level and sperm count with abnormal morphology increased in varicocele group, whereas total antioxidant status level decreased. In the VT group, all of the biochemical, molecular and histopathological changes detected in the varicocele group were statistically significantly reduced. When the findings obtained in this study are evaluated, it can be said that thymoquinone has the potential to be used as a preventive and therapeutic pharmacological agent in the medical treatment of varicocele. Although the exact mechanism of action of thymoquinone has not been fully elucidated, the findings obtained in this study support the view that thymoquinone showed a cytoprotective effect by reducing apoptosis, oxidative stress and lipid peroxidation.

Hindlimb unloading-induced reproductive suppression via Downregulation of hypothalamic Kiss-1 expression in adult male rats

BACKGROUND

Spaceflights-induced microgravity can alter various physiological processes in human's body including the functional status of the reproductive system. Rodent model of tail-suspension hindlimb unloading is extensively used to stimulate the organs responses to the microgravity condition. This study explores the potential effects of hindlimb unloading on testicular functions and spermatogenesis in adult male rats and the underlying mechanism/s.

METHODS

Twenty Sprague-Dawley rats were allotted into two groups: normally loaded group (control; all arms were in touch with the grid floor) and hindlimb unloaded group (HU; only the forearms were in contact with the grid floor).

RESULTS

Following 30 days of exposure, the HU group saw a decline in body weight, testicular and epidydimal weights, and all semen parameters. The circulating concentrations of gonadotropin-releasing hormone (GnRH), follicle stimulating hormone (FSH), luteinizing hormone (LH) and testosterone significantly decreased, while levels of kisspeptin, corticosterone, inhibin, prolactin and estradiol (E2) increased in the HU group. Intratesticular levels of 5α-reductase enzyme and dihydrotestosterone (DHT) were suppressed, while the levels of aromatase and kisspeptin were significantly elevated in the HU group. Hypothalamic kisspeptin (Kiss1) mRNA expression levels were downregulated while its receptors (Kiss1R) were upregulated in the HU group. On the contrary, the mRNA expression levels of testicular Kiss1 were upregulated while Kiss1R were downregulated. The pituitary mRNA expression levels of FSHβ and LHβ decreased in the HU group. The levels of the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and nitric oxide (NO) concentrations, and total antioxidant capacity (TAC) were elevated while malondialdehyde (MDA) concentrations declined in the testes of HU group. The testes of the HU rats showed positive immunostaining of caspase-3, heat shock protein 70 (HSP70) and Bcl2.

CONCLUSIONS

Altogether, these results revealed an inhibitory effect of hindlimb unloading on kisspeptin signaling in the hypothalamic-pituitary-testicular axis with impaired spermatogenesis and steroidogenesis.

Significant alterations of 6-keto prostaglandin F1a and NO levels in spermatic vein plexus patients with varicocele

To investigate the level variation of correlative factors between the spermatic vein plexus and peripheral blood in patients with varicocele, a total of 22 patients diagnosed with varicocele were enrolled in the study. All patients were performed a testicular artery-sparing microsurgical varicocelectomy. During the operation, a blood sample from the left spermatic vein plexus and a peripheral blood sample were collected. A radioimmunoassay was used to determine the 6-keto prostaglandin F1a (6-keto-PGF1a ). A colorimetric method was performed to determine the NO. The enzyme immunoassay method was used to determine the creatinine, urea nitrogen, adrenaline, noradrenaline, dopamine and 5-HT. The mean age of all patients was 29.3 ± 7.8 years. Compared with the level of 6-keto-PGF1a and NO in the peripheral blood, 6-keto-PGF1a and NO were significantly increased in left spermatic vein plexus (347.3 (230.8-415.1) versus 99.7 (80.4-119.9) pg/ml and 192.3 ± 178.5 versus 107.1 ± 73.6 μmol/L, p < .05). There were no differences in the level of creatinine, urea nitrogen, adrenaline, noradrenaline, dopamine and 5-HT between the peripheral blood and left spermatic vein plexus (p > .05). The 6-keto-PGF1a and NO concentrations in left spermatic vein plexus were significantly higher than that in peripheral blood patients with varicocele.

Chronic fluoride exposure-induced testicular toxicity is associated with inflammatory response in mice

Previous studies have indicated that fluoride (F) can affect testicular toxicity in humans and rodents. However, the mechanism underlying F-induced testicular toxicity is not well understood. This study was conducted to evaluate the sperm quality, testicular histomorphology and inflammatory response in mice followed F exposure. Healthy male mice were randomly divided into four groups with sodium fluoride (NaF) at 0, 25, 50, 100 mg/L in the drinking water for 180 days. At the end of the exposure, significantly increased percentage of spermatozoa abnormality was found in mice exposed to 50 and 100 mg/L NaF. Disorganized spermatogenic cells, vacuoles in seminiferous tubules and loss and shedding of sperm cells were also observed in the NaF treated group. In addition, chronic F exposure increased testicular interleukin-17(IL-17), interleukin-17 receptor C (IL-17RC), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in transcriptional levels, as well as IL-17 and TNF-α levels in translational levels. Interestingly, we observed that F treated group elevated testicular inducible nitric oxide synthase (iNOS) mRNA level and nitric oxide (NO) concentration. Taken together, these results indicated that testicular inflammatory response could contribute to chronic F exposure induced testicular toxicity in mice.

Increased Total Antioxidant Capacity in Seminal Plasma of Varicocele Patients: A Multivariate Analysis

To investigate seminal antioxidant systems and their correlation with hormonal pattern in varicocele patients, we studied 33 varicocele (VAR) patients (12 oligozoospermic, 21 normozoospermic) and 34 non-VARs (10 idiopathic oligozoospermic, 24 normozoospermic). Non-enzymatic total antioxidant capacity (TAC) was measured using H(2)O(2)-metamyoglobin, which generates the radical form, spectroscopically detectable, of the chromogen 2,2',-azinobis-3-ethylbenzothiazoline-6-sulphonate (ABTS): time till appearance (Lag) of ABTS*(-) signifies antioxidant concentration. Lag was significantly longer in VARs than controls suggesting ineffective utilization of antioxidants. A significant direct correlation (r = 0.65, p < 0.01) of Lag with sperm count was observed in non-VARs, while in VARs it was inverted, as well as with hematic FSH levels. A multivariate analysis including FSH, Lag, progressive spermatozoa, oligozoospermia and varicocele indicated a strong inverse correlation between FSH and motility (r(2) = 0.31, p > F = 0.0007), not modified by Lag (r(2) = 0.31, p > F = 0.002). Their inverse correlation with Lag may suggest that higher FSH levels, improving sperm antioxidant efficiency, counterbalance varicocele-induced dyspermia.

Coenzyme Q10 and male infertility

We had previously demonstrated that Coenzyme Q10 [(CoQ10) also commonly called ubiquinone] is present in well-measurable levels in human seminal fluid, where it probably exerts important metabolic and antioxidant functions; seminal CoQ10 concentrations show a direct correlation with seminal parameters (count and motility). Alterations of CoQ10 content were also shown in conditions associated with male infertility, such as asthenozoospermia and varicocele (VAR). The physiological role of this molecule was further clarified by inquiring into its variations in concentrations induced by different medical or surgical procedures used in male infertility treatment. We therefore evaluated CoQ10 concentration and distribution between seminal plasma and spermatozoa in VAR, before and after surgical treatment, and in infertile patients after recombinant human FSH therapy. The effect of CoQ10 on sperm motility and function had been addressed only through some in vitro experiments. In two distinct studies conducted by our group, 22 and 60 patients affected by idiopathic asthenozoospermia were enrolled, respectively. CoQ10 and its reduced form, ubiquinol, increased significantly both in seminal plasma and sperm cells after treatment, as well as spermatozoa motility. A weak linear dependence among the relative variations, at baseline and after treatment, of seminal plasma or intracellular CoQ10, ubiquinol levels and kinetic parameters was found in the treated group. Patients with lower baseline value of motility and CoQ10 levels had a statistically significant higher probability to be responders to the treatment. In conclusion, the exogenous administration of CoQ10 increases both ubiquinone and ubiquinol levels in semen and can be effective in improving sperm kinetic features in patients affected by idiopathic asthenozoospermia.

TNF-alpha and IL-6 affect human sperm function by elevating nitric oxide production

Many studies have reported the effects of cytokines on human sperm function, even though their role and the mechanisms involved remain unclear. The effects of increasing concentrations of the cytokines TNF-alpha and IL-6 on human sperm motility and viability were assessed, and the possible mechanisms involved were investigated. TNF-alpha and IL-6 significantly reduced progressive motility at higher concentrations in a dose- and time-dependent manner. No differences were observed in cell viability. Both cytokines increased nitric oxide production in a dose-dependent manner. TNF-alpha and IL-6 did not statistically differ in their detrimental effects on human spermatozoa. These results indicate that TNF-alpha and IL-6 have an effect on sperm function. This effect is possibly mediated via an increase in nitric oxide production.

Increased testicular 8-hydroxy-2'-deoxyguanosine in patients with varicocele

OBJECTIVES

To assess immunohistochemically 8-hydroxy-2'-deoxyguanosine (8-OHdG, a sensitive biological marker of oxidative damage and stress) in testicular tissue from patients with varicocele, to determine whether 8-OHdG is related to spermatogenesis, as oxidative stress in testicular DNA is associated with poor semen quality and reduced fertility.

PATIENTS, SUBJECTS AND METHODS

Testicular tissue samples were collected from the testes of 36 patients with varicocele and five normal volunteers. The mean (sd) age of the patients was 35.3 (5.4) years. The prevalence of immunostained germ cells among all the germ cells in >20 seminiferous tubules was calculated.

RESULTS

The mean (sd) sperm concentration and Johnsen's score in the varicocele group was lower than in the normal group, at 27.6 (11.8) vs 80.4 (21.7) million/mL (P < 0.001) and 7.6 (1.1) vs 9.0 (0.7), respectively (P < 0.05). In all patients, 8-OHdG was mainly expressed in the spermatogonia and spermatocytes in the seminiferous tubule. Immunostained germ cells correlated negatively with sperm concentration (r = -0.48, P = 0.01) and Johnsen's score (r = -0.46, P = 0.02), but not with follicle-stimulating hormone, luteinizing hormone or testosterone level. Immunostained germ cells were significantly more prevalent in the varicocele group, at 53.6 (5.7)%, than that in the normal group, at 14.3 (2.3)% (P < 0.001). The prevalence of immunostained germ cells and clinical grades were positively related; the ratio recorded for varicocele grades I, II and III was 38.0 (10.0)%, 41.0 (9.1)%, and 57.0 (9.3)%, respectively (grade I vs grade III, P < 0.05).

CONCLUSIONS

Increased 8-OHdG expression in the testis was associated with deficient spermatogenesis in infertile men with varicocele.

Effect of psychological stress on the L-arginine-nitric oxide pathway and semen quality

It has been reported that mental stress causes abnormality of spermiogram parameters. We investigated the effect of psychological stress on the L-arginine-nitric oxide (NO) pathway. Semen samples were collected from 29 healthy fourth semester medical students just before (stress) and 3 months after (non-stress) the final examinations. Psychological stress was measured by the State Anxiety Inventory questionnaire. After standard semen analysis, arginase activity and NO concentration were measured spectrophotometrically in the seminal plasma. Measurements were made in duplicate. During the stress period, sperm concentration (41.28 +/- 3.70 vs 77.62 +/- 7.13 x 10(6)/mL), rapid progressive motility of spermatozoa (8.79 +/- 1.66 vs 20.86 +/- 1.63%) and seminal plasma arginase activity (0.12 +/- 0.01 vs 0.22 +/- 0.01 U/mL) were significantly lower than in the non-stress situation, whereas seminal plasma NO (17.28 +/- 0.56 vs 10.02 +/- 0.49 micromol/L) was higher compared to the non-stress period (P < 0.001 for all). During stress there was a negative correlation between NO concentration and sperm concentration, the percentage of rapid progressive motility and arginase activity (r = -0.622, P < 0.01; r = -0.425, P < 0.05 and r = -0.445, P < 0.05, respectively). These results indicate that psychological stress causes an increase of NO level and a decrease of arginase activity in the L-arginine-NO pathway. Furthermore, poor sperm quality may be due to excessive production of NO under psychological stress. In the light of these results, we suggest that the arginine-NO pathway, together with arginase and NO synthase, are involved in semen quality under stress conditions.

Experimental varicocele in the rat: early evaluation of the nitric oxide levels and histological alterations in the testicular tissue

The relationship between varicocele and male infertility remains to be explained. Oxidative damage because of the testicular venous backflow may represent one of the causes of gonad injury and seems to precede the histological alteration. Therefore measuring the values of spermatic or intratesticular nitric oxide (NO) could be useful in evaluating this oxidative distress. The aim of this study is to assess the role of testicular NO in early detection of the damages induced by an experimental varicocele in the Wistar rat. A left varicocele was induced in 10 animals (group A). A control group of 10 rats was performed (group B). Animals were killed 3 months after the operation. Both testicles were harvested, weighed and sectioned in two equal parts: one for the evaluation of the NO level and the other one for histological examination. All the rats in group A showed a conspicuous dilatation of the left spermatic vein. The histopathological analysis was normal in both the groups. Biochemistry showed a meaningful statistical difference (P < 0.001) in the concentrations of NO among the specimens of the left and right gonads in group A but no difference was found in group B. The increase in NO values and the presence of other oxidant agents represent the first sign of testicular distress and it seems to anticipate histopathological changes. As it is well known that a great difference exist between human and animal sperm, NO could therefore in the future be taken into consideration together with others parameters for the evaluation of patient who is affected by varicocele.

Testicular oxidative stress. Effects of experimental varicocele in adolescent rats

OBJECTIVE

This present study was undertaken to determine the levels of malondialdehyde (MDA), nitric oxide (NO) and total antioxidant status (TAS) in testes of adolescent rats with experimental bilateral varicocele and to determine the effects of oxidative stress on testis produced by varicocele.

METHODS

6-week-old, male Wistar rats, weighing 146-334 g (228.37 +/- 41.34 g), were randomly allocated into two groups. The first group underwent selective and bilateral partial ligation of the spermatic vein (n = 28), and the second group underwent a sham operation and served as the controls (n = 15). Animals were sacrificed 12 weeks after surgery and dilatation of the spermatic veins was observed in the first study group. Bilateral orchiectomy was performed in all rats, and MDA, NO and TAS levels were measured.

RESULTS

In the study group, the mean MDA (SEM) level was 15.58 +/- 6.07 micromol/g protein, and in the control group, it was 11.59 +/- 3.86 micromol/g protein, respectively; this difference was statistically significant (p < 0.05). The mean NO level was 82.73 +/- 77.84 nmol/g protein in the study group, whereas 28.65 +/- 20.18 nmol/g protein in the control group, this difference was also statistically significant (p < 0.005). The mean TAS levels of the study and control groups were 0.91 +/- 0.32 and 1.78 +/- 0.46 nmol/g tissue, respectively, and this difference was also statistically significant (p < 0.001). But there was no correlation between these three parameters (MDA<-->TAS: r = -0.103, p > 0.05; MDA<-->NO: r = -0.104, p > 0.05; NO<-->TAS: r = -0.123, p > 0.05).

CONCLUSION

These findings suggest that varicocele may change the testicular oxidative status and may play a role in testicular dysfunction that causes infertility.

An update of Coenzyme Q10 implications in male infertility: biochemical and therapeutic aspects

This review is focused upon the role of coenzyme Q(10) in male infertility in the light of a broader issue of oxidative damage and antioxidant defence in sperm cells and seminal plasma. Reactive oxygen species play a key pathogenetic role in male infertility besides having a well-recognized physiological function. The deep involvement of coenzyme Q(10) in mitochondrial bioenergetics and its antioxidant properties are at the basis of its role in seminal fluid. Following the early studies addressing its presence in sperm cells and seminal plasma, the relative distribution of the quinone between these two compartments was studied in infertile men, with special attention to varicocele. The reduction state of CoQ(10) in seminal fluid was also investigated. After the first in vitro experiments CoQ(10) was administered to a group of idiopathic asthenozoospermic infertile patients. Seminal analysis showed a significant increase of CoQ(10) both in seminal plasma and in sperm cells, together with an improvement in sperm motility. The increased concentration of CoQ(10) in seminal plasma and sperm cells, the improvement of semen kinetic features after treatment, and the evidence of a direct correlation between CoQ(10) concentrations and sperm motility strongly support a cause/effect relationship. From a general point of view, a deeper knowledge of these molecular mechanisms could lead to a new insight into the so-called unexplained infertility.

Increased nitric oxide is accompanied by lipid oxidation in adolescent varicocele

Summary One of the mechanisms of injury in varicocele has been proposed to be elevated nitric oxide (NO). We aimed to determine the association between the elevation of NO and lipid oxidation in varicocele compared with peripheral venous levels of these two substances as it has not been studied before. The study group consisted of 13 adolescents with left idiopathic varicocele of grades II-III. Blood specimens were obtained from dilated spermatic and peripheral veins simultaneously. Peripheral samples were also collected from 13 healthy children as controls. Nitrite/nitrate levels (NO(x)) and levels of malonedialdehyde (MDA) were determined using Griess reaction and thiobarbituric acid test, respectively. Results were compared with Kruskal-Wallis and Mann-Whitney tests. Peripheral NO(x) and MDA were the same in the study and control groups (p = 0.069 and p = 0.27, respectively). Spermatic vein NO(x) and MDA levels were elevated significantly compared with the peripheral levels in the study group (p = 0.005 and p = 0.048, respectively). Increased NO(x) levels with lipid oxidation occur locally in adolescent varicocele, implying that these events could be reversed by early treatment.

Testicular tissue nitric oxide and thiobarbituric acid reactive substance levels: evaluation with respect to the pathogenesis of varicocele

The aim of the present study is to evaluate tissue nitric oxide (NO) and thiobarbituric acid reactive substance (TBARS) levels in testicular tissue, and to determine their relationship with seminal parameters in order to explain possible effects on varicocele pathophysiology. Ten adult male Wistar rats at 8 weeks old underwent partial left renal vein ligation. A sham operation was performed on control rats in a second group of another ten rats. All animals were killed 4 weeks after surgery. The testes were removed and histological changes were observed by light microscopy with haematoxylin and eosin stain on half of each testis. The rest of testis was used for the evaluation of testicular tissue NO and TBARS levels. Epididymal aspirated seminal plasma was used for semen analysis and morphological analysis was carried out according to Kruger's criteria. Statistical analysis was performed by using Mann-Whitney U-tests and Spearman rank correlations between the two groups for NO and TBARS levels and for seminal parameters. Testicular tissue NO and TBARS levels (mean+/-SEM) were 62.8+/-10.1 micromol/g protein and 4.7+/-0.3 nmol/g protein in group 1. These parameters were 16.9+/-2.2 micromol/g protein and 3.1+/-0.2 nmol/g protein in the group 2 controls. There were significant differences between these parameters ( P(NO)=0.000, P(TBARS)=0.001). Although a positive and significant correlation between testicular tissue NO and TBARS levels was found ( r(s)=0.739, P=0.014), there was only a strong negative correlation between NO levels and sperm motility in group 1 ( r(s)=-0.815, P=0.004). We found that this effect of NO on sperm motility was independent from TBARS levels after regression analysis ( r(2)=-0.687, beta=0.825, P=0.034). Although there were statistically significant differences in seminal parameters between the two groups, there was no difference between them in the histopathological examination. We found that sperm motility was significantly related to testicular tissue NO levels only. Thus, we suggest that NO is an important mediator in the pathogenesis of varicocele. TBARS and other substances have been effective via NO pathways.

Total antioxidant capacity in patients with varicoceles

OBJECTIVE

To explore a possible molecular defect linked to infertility, studying total antioxidant capacity (TAC) of seminal plasma in varicocele (VAR).

DESIGN

Case-series study.

SETTINGS

Volunteers in an academic research environment and out-patients in clinical service.

PATIENT(S)

Twenty-five VAR patients (9 oligospermic and 16 normospermic) vs 24 non-VAR controls (7 subjects with idiopathic oligospermia and 17 normospermic subjects).

INTERVENTION(S)

Evaluation of seminal plasma TAC.

MAIN OUTCOME MEASURE(S)

TAC was measured using myoglobin, as a source of radicals, which interact with a chromogen 2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonate) (ABTS), whose radical cation is spectroscopically detectable. The latency phase (Lag) in the accumulation of ABTS cation is proportional to antioxidant concentration.

RESULT(S)

Lag showed significantly greater values in the all VAR patients vs non-VAR subjects. Oligospermic-VAR patients showed the greatest values. Lag and sperm motility significantly correlated in VAR normospermic patients. Follicle-stimulating hormone (FSH) showed significant inverse association with Lag in same group.

CONCLUSION(S)

The augmented Lag values could indicate an ineffective utilization of antioxidants in oligospermic-VAR, while in normo-VAR the direct correlation between TAC and motility suggest a potential protective role toward sperm motility. In the same group, the inverse correlation with FSH suggests that greater FSH levels induce a better utilization of antioxidants by spermatozoa.

The changes in testicular vascular permeability during progression of the experimental varicocele

OBJECTIVES

The vascular permeability of testicular capillaries which play a role in controlling the formation of testicular interstitial fluid was studied during the progressive course of experimental varicocele.

MATERIALS AND METHODS

The pathology was developed through partial ligation of left renal vein in four groups of rats. Controls of each group were subjected to sham surgery. After different periods of varicocele creation (1, 3, 6 and 14 weeks), animals' testes per one of the study groups were extirpated and weighed. The volume density percentages of polymorphnuclear leukocytes (PMN) per testicular blood vessels; which are markers of the increase in vascular permeability, were also estimated in both testes. To further verify the obtained findings, another group of animals received human chorionic gonadotrophin (hCG) treatment 6 weeks after varicocele creation and their histopathological sections were examined.

RESULTS

Animal testes' of (1 and 3 weeks) groups were found to be significantly heavier (p<0.05) than their controls. PMN showed accumulation in testicular blood vessels and their volume density percentages per these blood vessels in both testes were significantly higher in each study group than in those of its controls. However, these percentages showed gradual significant decline as the duration of varicocele bearing gradually increased. The hCG-treated animals revealed more accumulation of the PMN in their histopathological sections.

CONCLUSION

The present results suggest that experimental varicocele may induce an increase in testicular vascular permeability, which then decreases gradually with time. It is supposed that parallel changes in the rate of formation of testicular interstitial fluid may be accompanied. The results have also showed that the vasculature of the testis with experimental varicocele can still respond to hCG.

Guanylate cyclase activity and sperm function

In species with external fertilization, the guanylate cyclase family is responsible for the long-distance interaction between gametes, as its activation allows sperm chemotaxis toward egg-derived substances, gamete encounter, and fertilization. In species with internal fertilization, guanylate cyclase-activating substances, which are secreted by several tissues in the genital tracts of both sexes, deeply affect sperm motility, capacitation, and acrosomal reactivity, stimulating sperm metabolism and promoting the ability of the sperm to approach the oocyte, interact with it, and finally fertilize it. A complex system of intracellular pathways is activated by guanylate cyclase agonists in spermatozoa. Sperm motility appears to be affected mainly through an increase in intracellular cAMP, whereas the acrosome reaction depends more directly on cyclic GMP synthesis. Both cyclic nucleotides activate specific kinases and ion signals. A complex cross-talk between cAMP- and cyclic GMP-generating systems occurs, resulting in an upward shift in sperm function. Excessive amounts of certain guanylate cyclase activators might exert opposite, antireproductive effects, increasing the oxidative stress on sperm membranes. In view of the marked influence exerted by guanylate cyclase-activating substances on sperm function, it seems likely that guanylate cyclase activation or inhibition may represent a new approach for the diagnosis and treatment of male and/or female infertility.

Seminal plasma nitric oxide concentration in oligo- and/or asthenozoospermic subjects with/without varicocele

There is an inverse correlation between seminal plasma nitric oxide (NO) concentration and sperm parameters (motility and concentration) in patients with varicocele. This study investigated whether this occurs in patients with oligo- and/or asthenozoospermia due to causes other than varicocele. A total of 69 (19 with varicocele and oligo- and/or asthenozoospermia [group 1], 30 from oligo- and/or asthenozoospermic ones without varicocele [group 2], and 20 from healthy subjects [control group]) semen samples were analyzed. While group 1 had a significantly higher NO concentration in the seminal plasma compared to both the control group and group 2, there was no significant difference between group 2 and the control group (p >.05). In group 1, but not in the other groups, there was an inverse correlation between the seminal plasma NO concentration and sperm motility and concentration. NO production could be specifically related to the varicocele, since NO production in oligo- and/or asthenozoospermia cases without varicocele is not increased.

Oxidative stress, spermatogenesis and fertility

Reactive oxygen species production and glutathione depletion in mammalian male germ cells are physiological events that are requisite to the functional maturation and capacitation of spermatozoa. In relation to this oxidative stress, an oxidation of the bulk of protein sulfydryl groups takes place during the final phases of male germ cell maturation. The selenoenzyme phospholipid hydroperoxide glutathione peroxidase catalyzes this reaction, and accounts for both the assembly of the mid-piece of spermatozoa and chromatin condensation. This process highlights the role of H2O2 and selenium in spermatogenesis and provides a mechanism for coupling a 'physiologically controlled' oxidative stress to a specialized phenotypic function.