The participation of cyclic nucleotides and protein kinase in the regulation of norepinephrine synthesis and release during nerve stimulation

Considerable evidence has accumulated in recent years to suggest that cyclic AMP-dependent protein kinase is responsible for the activation of tyrosine hydroxylase following nerve stimulation. Since stimulation of the central nervous system either by electrical impulses or by exposure of intact brain tissue to depolarizing concentrations of potassium is associated with an activation of adenylate cyclase and an increase in cyclic AMP, it is possible that the normal physiological mechanism by which catecholamine synthesis is enhanced during nerve stimulation involves modification of the enzyme by protein kinase. It has been demonstrated that, in the presence of cyclic AMP, ATP, Mg++ and protein kinase, purified preparations of tyrosine hydroxylase are directly phosphorylated. Since cyclic nucleotides also have been implicated in the process of neurally mediated transmitter release, it is conceivable that activation of adenylate cyclase presynaptically is a common mechanism by which both catecholamine synthesis and norepinephrine release are enhanced during nerve stimulation. Although agonists and antagonists of many putative presynaptic receptors have been found to modulate norepinephrine release during nerve stimulation, no convincing evidence has yet been obtained to suggest that alteration of presynaptic adenylate cyclase activity consequent to nerve stimulation is mediated by a presynaptic action of one or more of these neuromodulators. It is possible that direct depolarization of the nerve terminal in some manner results in activation of presynaptic adenylate cyclase, perhaps by a mechanism involving calcium.

Undernutrition affects cell survival, oxidative stress, Ca2+ handling and signaling pathways in vas deferens, crippling reproductive capacity

Background

The aim of this work was to investigate the mechanisms by which chronic malnutrition (CM) affects vas deferens function, leading to compromised reproductive capacity. Previous studies have shown that maternal malnutrition affects the reproductive tracts of adult male offspring. However, little is known about the effects of CM, a widespread life-long condition that persists from conception throughout growth to adult life.

Methodology/Principal Findings

Young adult male rats, which were chronically malnourished from weaning, presented decreased total and haploid cells in the vas deferens, hypertrophy of the muscle layer in the epididymal portion of the vas deferens and intense atrophy of the muscular coat in its prostatic portion. At a molecular level, the vas deferens tissue of CM rats exhibited a huge rise in lipid peroxidation and protein carbonylation, evidence of an accentuated increase in local reactive oxygen species levels. The kinetics of plasma membrane Ca²⁺-ATPase activity and its kinase-mediated phosphorylation by PKA and PKC in the vas deferens revealed malnutrition-induced modifications in velocity, Ca²⁺ affinity and regulation of Ca²⁺ handling proteins. The severely crippled content of the 12-kDa FK506 binding protein, which controls passive Ca²⁺ release from the sarco(endo) plasmic reticulum, revealed another target of malnutrition related to intracellular Ca²⁺ handling, with a potential effect on forward propulsion of sperm cells. As a possible compensatory response, malnutrition led to enhanced sarco(endo) plasmic reticulum Ca²⁺-ATPase activity, possibly caused by stimulatory PKA-mediated phosphorylation.

Conclusions/Significance

The functional correlates of these cellular and molecular hallmarks of chronic malnutrition on the vas deferens were an accentuated reduction in fertility and fecundity.

Activity of alpha- and beta-mannosidases in semen and reproductive organs of the drake

The activity of alpha- and beta-mannosidase (alpha-MAN and beta-MAN) in seminal plasma, spermatozoa and homogenates of reproductive organs has been determined in the drake. The highest specific activities of the examined mannosidases were found in epididymides. The activities of both enzymes decreased significantly during the postbreeding resting season compared to the breeding season. Elution profiles of multiple forms of mannosidases from particular organs were obtained and characterized. It was found that alpha- and beta-mannosidases in the genital tract of the drake are similar to the enzymes described in other species of domestic fowl. The presence of highly active mannosidases in reproductive tissues and a decline of the mannosidase activities during the postbreeding season strongly suggests that the enzymes take part in reproductive processes of birds.

Localization of cyclooxygenase-2 in mice vas deferens and its effects on fertility upon suppression using nimesulide: a preferential cyclooxygenase-2 inhibitor

Accumulating evidence on constitutive expression of cyclooxygenase-2 (COX-2), one of the isoforms of enzyme cyclooxygenase (COX) the other isoform being cyclooxygenase-1 (COX-1), questions the safety profile of non-steroidal anti-inflammatory drugs (NSAIDs). This COX-2 isoform which is induced not only during inflammation but also by factors such as cytokines, steroid hormones and mitogenic stimuli is constitutively expressed in brain, kidney and reproductive organs. Present NSAIDs, particularly COX-2 inhibitors is no longer considered safe since suppression of COX-2 in tissues which it is constitutively expressed may lead to adverse effects. Though intense expression of COX-2 in vas deferens is proved, lack of information with respect to its function has attracted a wide scope for research as to whether COX-2 in vas deferens contributes to male fertility. In the present study, the authors investigated the localization of COX-2 as well as COX-1 in mice vas deferens and also assessed the activity of COX-2 and total prostaglandin (PG) levels in vas deferens. Further they suppressed the expression of COX-2 using a preferential COX-2 inhibitor nimesulide and analyzed the sperm from vas deferens for any defects. COX-2 was intensely expressed in the epithelial cells of mice vas deferens and nimesulide was able to effectively suppress most of COX-2 expression. A decrease in PG levels was observed initially but interestingly, the levels tend to rise on sustained suppression of COX-2. The motility of sperm was affected severely after 6h of nimesulide administration that suggested a crucial role of COX-2 towards fertility of mice sperm.

RNase9, an Androgen-Dependent Member of the RNase A Family, Is Specifically Expressed in the Rat Epididymis1

Members of the RNase superfamily participate in a diverse array of biological processes, including RNA degradation, antipathogen activities, angiogenesis, and digestion. In the present study, we cloned the rat RNase9 gene by in silico methods and genome walking based on homology to the Macaca mulatta (rhesus monkey) epididymal RNase9. The gene is located on chromosome 15p14, spanning two exons, and is clustered with other members of the RNase A superfamily. It contains 1279 bp and encodes 182 amino acids, including a 24-amino acid signal peptide, and it has unique features known from other RNases. Unlike those other members, the rat RNase9 mRNA was specifically expressed in the epididymis, especially in the caput and corpus, and exhibited an androgen-dependent expression pattern but was downregulated in an epididymitis animal model. The RNASE9 was expressed in a principal cell-specific pattern. Interestingly, most of the principal cells in the caput expressed the RNASE9; however, in the distal caput, the principal cells showed a checkerboard-like pattern of immunoreactivity. We also observed that the RNASE9 was bound on the acrosomal domain of sperm. Its potential roles in sperm maturation are discussed.

Carbonic anhydrase activity in the vas deferens of the cotton leafworm - Spodoptera littoralis (Lepidoptera: Noctuidae) controlled by circadian clock

The male reproductive tract of Lepidoptera is an ideal model for the study of the physiological role of peripheral clocks in insects. The latter are significant in the generation and coordination of rhythmic phenomena which facilitate the initial stages of sperm capacitation. This process requires the maintenance of pH in the upper vas deferens (UVD) aided by, among others, H+-ATPase. Our aim was to determine the potential involvement of carbonic anhydrase (CA) in this process, an enzyme tasked with generating protons subsequently utilized by H+-ATPase to acidify the UVD milieu in S. littoralis, during the time when the lumen of this organ is filled with sperm. We attempted to answer the question whether CA activity can be controlled by the biological oscillator present in the male reproductive tract of the cotton leafworm. Using PAGE zymography, the presence of CA was demonstrated in the UVD wall, but not in the luminal fluid nor in the sperm. Using histochemistry, it was shown that CA is active in the UVD epithelium, and that this activity varies throughout the day and is most likely controlled by an endogenous biological clock. Conversely, the application of CA inhibitors, acetazolamide and sodium thiocyanate, in conjunction with an analysis of H+-ATPase activity in the acidification the UVD environment shows that CA most likely does not play a direct role in the regulation of the pH in this organ.

Adaptive expression pattern of different proteins involved in cellular calcium homeostasis in denervated rat vas deferens

The activity and protein expression of plasma membrane and sarco(endo)plasmic reticulum (Ca2+-Mg2+)ATPases and ryanodine receptors were investigated in surgically denervated rat vas deferens. The function of thapsigargin-sensitive but not thapsigargin-resistant (Ca2+-Mg2+)ATPase (from sarco(endo)plasmic reticulum and plasma membrane, respectively), evidenced by enzyme activity and Ca2+ uptake experiments, was significantly depressed by 30-50% when compared to innervated vas. Western blots showed that such reduction in sarco(endo)plasmic reticulum (Ca2+-Mg2+)ATPase performance was accompanied by a decrement of similar magnitude in sarco(endo)plasmic reticulum (Ca2+-Mg2+)ATPase type 2 protein expression, without any significant change in plasma membrane (Ca2+-Mg2+)ATPase expression. Finally, [3H]ryanodine binding revealed that the density of ryanodine binding sites was reduced by 45% after denervation without modification in affinity. The present findings demonstrate that sarco(endo)plasmic reticulum proteins involved in intracellular calcium homeostasis are clearly down-regulated and brings further evidence of a modified calcium translocation in denervated rat vas deferens.

On the mechanism of biosynthesis of 19-hydroxyprostaglandins of human seminal fluid and expression of cyclooxygenase-2, PGH 19-hydroxylase (CYP4F8) and microsomal PGE synthase-1 in seminal vesicles and vas deferens

The predominating prostaglandins of human seminal fluid are 19R-hydroxyprostaglandins E1 and E2, conceivably formed sequentially by prostaglandin H (PGH) synthase-2, PGH 19-hydroxylase (CYP4F8), and microsomal PGE synthase-1 of seminal vesicles. Our aim was to study this enzyme system. Quantification by real-time PCR suggested that the transcripts of PGH synthase-2, CYP4F8, and microsomal PGE synthase-1 were abundant and correlated in seminal vesicles of seven patients (p < 0.05). The three enzymes were detected in seminal vesicles by Western blot analysis, and immunohistological analysis confirmed the localization to the epithelia of seminal vesicles and distal vas deferens. Immunofluorescence analysis showed co-localization of the three enzymes in epithelial cells of seminal vesicles and vas deferens. 19-Hydroxy-PGE compounds were detected by mass spectrometry in the mucosa of distal vas deferens. Recombinant CYP4F8 catalyzes n-2 hydroxylation of PGH1 and PGH2 and n-3 hydroxylation of arachidonic acid. Arachidonic acid was oxidized to 18-hydroxyarachidonic acid and to PGE2 and by microsomes of seminal vesicles in the presence of NADPH and GSH, and to relatively small amounts of 19-hydroxy-PGE2. We conclude that PGH synthase-2, CYP4F8, and PGE synthase-1 likely forms 19-hydroxy-PGE compounds in seminal vesicles and vas deferens, but the catalytic properties of CYP4F8 suggest additional biological functions. Recombinant CYP4F8 was also found to catalyze n-2 hydroxylation of PGI2 and carbaprostacyclin (Km to approximately 40 microM), and n-2 and n-3 hydroxylation of carbocyclic TXA2.

The in vitro and in vivo pharmacological activity of Boiga dendrophila (mangrove catsnake) venom

The great taxonomic and prey base diversity of colubrids (non-front-fanged snakes) suggests that their venoms may represent a 'literal gold mine' for scientists eager to find novel pharmacological probes. While pharmacological characterization is lacking for most of these venoms, this is even more so with regard to activity of colubrid venoms on the mammalian autonomic nervous system. This study characterizes the activity of venom from the colubrid, Boiga dendrophila using in vitro smooth muscle preparations and the anaesthetized rat. In the prostatic segment of the rat vas deferens, cumulative additions of venom (1-150 microg ml(-1)) induced concentration-dependent inhibition of electrically evoked (0.2 Hz, 0.3 ms, 70-100 V) twitches. The inhibitory effect of venom (100 microg ml(-1)) was attenuated by 8-phenyltheophylline (8-PT) (20 microM) and 8-cyclopentyl-1, 3-dipropylxanthine (20 microM) but not idazoxan (1 microM), or a combination of ranitidine (0.2 microM) and thioperamide (10 microM). The inhibitory effect of venom (100 microg ml(-1)) was augmented by dipyridamole (10 microM) but abolished by pretreatment with adenosine deaminase (7.5 units/100 microl) suggesting that it contains components with adenosine A(1) receptor activity, most likely adenosine. In isolated segments of guinea-pig ileum, venom (10-100 microg ml(-1)) caused concentration-dependent contractions which were inhibited by the muscarinic receptor antagonist atropine (0.1 microM) but not by the histamine receptor antagonist mepyramine (0.5 microM). In the anaesthetized rat, venom (5-7.5 mg kg(-1), i.v.) caused a hypotensive effect. Our data suggest that the venom contains components with purinergic and muscarinic receptor activity.

Expression and functional activity of phosphodiesterase type 5 in human and rabbit vas deferens

The molecular mechanisms underlying the regulation of vas deferens (VD) motility and semen emission are still poorly understood. We now report evidence on VD expression of phosphodiesterase type 5 (PDE5), which regulates nitric oxide (NO)-induced relaxation and cGMP breakdown in smooth muscle cells. In human VD, the PDE5 abundance was relatively high (>3 x 10(6) molecules/microg total RNA), although 10-fold lower than in corpora cavernosa (CC). Also cGMP metabolising activity was higher in CC than in VD. However, both tissues share the same sensitivity to a broad panel of cGMP-related PDE inhibitors: sildenafil, tadalafil, dipyridamole, zaprinast, vinpocetine, EHNA and cilostamide. Based on the rank order of potency of these PDE inhibitors, we found that the cGMP metabolizing activity in human VD mostly corresponds to PDE5. PDE5 was immunolocalized in all the muscular layers of human and rabbit VD and was found to be negatively involved in regulating NO-induced relaxation. In addition, by using a rabbit model of hypogonadotropic hypogonadism, we found that PDE5 gene expression and activity are androgen-dependent in VD, as previously demonstrated in CC. In fact, the sensitivity to a NO-donor (NCX4040), its enhancement by PDE5 inhibitors and the PDE5-related cGMP breakdown were all affected by androgen manipulation. Our results provide a hypothesis explaining the beneficial effects of PDE inhibitors in patients with rapid ejaculation.

Effects of cooling and ARL 67156 on synaptic ecto-ATPase activity in guinea pig and mouse vas deferens

We have studied the influence of temperature and ARL 67156 on ATP hydrolysis in mouse and guinea pig vas deferens in order to explore the properties of the enzymatic inactivation mechanism proposed to regulate purinergic neurotransmission at the sympathetic neuromuscular junction of smooth muscle. The ectonucleotidase activity was determined by using the malachite green method to measure the inorganic phosphate (Pi) liberated with ATP used as a substrate. ATP hydrolysis in both species was found to be insensitive to ouabain (100 microM), sodium azide (1 mM), sodium vanadate (100 microM) and beta-glycerophosphate (10 mM) and was also found to depend on Ca2+ and Mg2+. V(MAX) of the ectonucleotidase activity for guinea pig and mouse vas deferens was 958.4+/-66.3 and 79.7+/-8.5 pmol/min/mg, while K(M) was 625.1+/-45.2 and 406.0+/-29.0 microM, respectively. Cooling the tissues from 35 to 25 degrees C reduced the enzyme activity significantly (P<0.01) by 52.7+/-9.2% in guinea pig vas deferens and 34.9+/-5.3% in mouse vas deferens. ARL 67156 (100 microM), the specific ecto-ATPase inhibitor, caused a reduction in enzyme activity in guinea pig and mouse vas of 54.1+/-16.4% and 53.0+/-7.6%, respectively (P<0.01). The degree of inhibition of ATP hydrolysis by lowered temperature and 100 microM ARL 67156 correlates well with the reported potentiation and prolongation of junction potentials under these conditions. It is concluded that ecto-ATPase or a closely related ectonucleotidase plays an important role in the physiological regulation of purinergic neurotransmission.

Androgens regulate phosphodiesterase type 5 expression and functional activity in corpora cavernosa

By real-time RT-PCR and Western blot analysis, we found that phosphodiesterase type 5 (PDE5) mRNA and protein abundance was several fold higher in human male than in female reproductive tracts. The highest mRNA level (>1 x 10(7) molecules/microg total RNA) was detected in human corpora cavernosa (CC), where PDE5 protein was immunolocalized in both muscular and endothelial compartment. The possible role of androgens in regulating PDE5 expression was studied using a previously established rabbit model of hypogonadotropic hypogonadism. In this model, hypogonadism reduced, and testosterone (T) supplementation restored, CC PDE5 gene and protein expression. In addition, T supplementation completely rescued and even enhanced cyclic GMP conversion to metabolites, without changing IC(50) for sildenafil (IC(50) = 2.16 +/- 0.62 nm). In control CC strips, sildenafil dose-dependently increased relaxation induced by electrical field stimulation, with EC(50) = 3.42 +/- 1.7 nm. Hypogonadism reduced, and T increased, sildenafil effect on electrical field stimulation, again without changing their relative EC(50) values. CC sensitivity to the NO-donor NCX4040 was greater in hypogonadal rabbit strips than in control or T-treated counterparts. Moreover, sildenafil enhanced NCX4040 effect in eugonadal rabbit strips but not in hypogonadal ones. This suggests that androgens up-regulate PDE5 in rabbit penis. We also measured PDE5 gene expression and metabolic activity in human CC from male-to-female transsexual individuals, chronically treated with estrogens and cyproterone acetate. Comparing the observed values vs. eugonadal controls, PDE5 mRNA, protein, and functional activity were significantly reduced. In conclusion, we demonstrated, for the first time, that androgens positively regulate PDE5, thus providing a possible explanation about the highest abundance of this enzyme in male genital tract.

Phenylephrine Induces Endogenous Noradrenaline Release in the Rat Vas deferens through Nitric Oxide Synthase Pathway

We have previously observed that in the rat vas deferens nitric oxide synthase pathway potentiated phenylephrine-induced contractility raising the possibility of a facilitatory role on neurotransmission by nitric oxide. To confirm this hypothesis we studied the effect of phenylephrine on the concentration response curves obtained in preparations from reserpine-treated rats in the absence and presence of the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (L-NMMA). The endogenous noradrenaline released by normal preparations (without reserpine) was measured in the perfusion fluid of preparations stimulated with phenylephrine, in the absence and presence of L-NMMA, L-NMMA + the nitric oxide donor 3-morpholinosydnonimine hydrochloride (SIN-1), the alpha1-adrenoceptor antagonist prazosin and the blocker of noradrenaline carrier desipramine. The phenylephrine-induced noradrenaline release in a calcium-free medium was also measured. L-NMMA decreased the Emax of phenylephrine concentration response curves obtained in preparations from normal (reserpine-untreated) but not from reserpine-treated rats. In the perfusion fluid of preparations incubated with phenylephrine, a concentration-dependent increase of noradrenaline was observed which was reversed by L-NMMA and restored when SIN-1 was added together with the nitric oxide synthase inhibitor. The concentration-dependent phenylephrine-induced noradrenaline increase was not modified by desipramine but was abolished by 10 microM prazosin. In calcium-free medium, phenylephrine failed to increase the noradrenaline concentration. These results suggest that in the rat vas deferens, nitric oxide pathway potentiates the phenylephrine-induced contractility through a mechanism which involves calcium-dependent release of endogenous noradrenaline and seems to depend, at least partially on the activation of alpha1-adrenoceptors.

Acquisition of arylsulfatase A onto the mouse sperm surface during epididymal transit

Arylsulfatase A (AS-A) is localized to the sperm surface and participates in sperm-zona pellucida binding. We investigated how AS-A, usually known as an acrosomal enzyme, trafficked to the sperm surface. Immunocytochemistry of the mouse testis confirmed the existence of AS-A in the acrosomal region of round and elongating spermatids. However, immunofluorescence and flow cytometry indicated the absence of AS-A on the surface of live testicular sperm. In contrast, positive AS-A staining was observed in the heads of live caudal epididymal and vas deferens sperm. The results suggested that acquisition of AS-A on the sperm surface occurred during epididymal transit. Immunocytochemistry of the epididymis revealed AS-A in narrow and apical cells in the initial segment and in clear cells in all epididymal regions. However, these epithelial cells are in the minority and are not involved in secretory activity. In the caudal epididymis and vas deferens, AS-A was also localized to principal cells, the major epithelial cells. Because principal cells have secretory activity, they may secrete AS-A into the epididymal fluid. This hypothesis was supported by our results revealing the presence of AS-A in the epididymal and vas deferens fluid (determined by immunoblotting and ELISA) and an AS-A transcript in the epididymis (by reverse transcription polymerase chain reaction). Alexa-430 AS-A bound to epididymal sperm with high affinity (Kd = 46 nM). This binding was inhibited by treatment of sperm with an antibody against sperm surface sulfogalactosylglycerolipid. This finding suggests that AS-A in the epididymal fluid may deposit onto sperm via its affinity to sulfogalactosylglycerolipid.

Transgenic mouse with high Cre recombinase activity in all prostate lobes, seminal vesicle, and ductus deferens

BACKGROUND

Prostate-specific gene ablation provides a powerful tool for functional characterization of genes that have impact on embryonic development or on other organs, specifically in the prostate. Uniform expression of Cre with high recombinase activity in the prostate is needed for prostate-specific gene ablation based on Cre-loxP recombinations. Currently, available strains of Cre transgenic mice only express Cre recombinase adequately in certain lobes of the prostate. In other lobes, the expression is low and mosaic. Additional strains of transgenic mice expressing high levels of prostate-specific Cre in all prostate lobes would be useful to study the impact of genome manipulation in all prostate lobes.

METHODS

The ARR2PB composite promoter with improved capacity to drive androgen-responsive gene expression was used to initiate expression of a transgene bearing the cDNA encoding a recently modified Cre recombinase with improved recombination activity. In addition, an insulator element from the chicken globin locus that minimized negative effect on transcription of the transgene imposed by chromosome structure was employed. The derived transgenic founders were crossed with the Z/AP reporter mouse and Fgfr2(f/f) mice bearing loxP flanking the FGFR2 locus. Immunochemical and mRNA analyses were employed to test expression and efficacy of the Cre recombinase in the prostate and other tissues.

RESULTS

The ARR2PBi-Cre transgenic mouse specifically and uniformly expressed Cre recombinase in the dorsal, lateral, ventral, and anterior lobes of the prostate, seminal vesicles, and ductus deferens. The Cre recombinase in these tissues effectively excised loxP flanked DNA fragments in the Z/AP reporter that triggered expression of beta-galactosidase, and the loxP-flanked FGFR2(f/f) locus resulting in specific ablation of FGFR2 in the prostate.

CONCLUSIONS

Compared with the currently available prostate-specific Cre strains, the new ARR2PBi-Cre strain exhibited higher and more uniform expression of Cre recombinase in the prostate as well as in seminal vesicles and ductus deferens. This provides an additional tool for efficient hormone-dependent gene targeting in epithelial cells of all lobes of the adult prostate, seminal vesicle, and ductus deferens.

Evidence for trichloroethylene bioactivation and adduct formation in the rat epididymis and efferent ducts

Recent studies indicate that trichloroethylene (TCE) may be a male reproductive toxicant. It is metabolized by conjugation with glutathione and cytochrome p450-dependent oxidation. Reactive metabolites produced along both pathways are capable of forming protein adducts and are thought to be involved in TCE-induced liver and kidney damage. Similarly, in situ bioactivation of TCE and subsequent binding of metabolites may be one mechanism by which TCE acts as a reproductive toxicant. Cysteine-conjugate beta-lyase (beta-lyase) bioactivates the TCE metabolite dichlorovinyl cysteine (DCVC) to a reactive intermediate that is capable of binding cellular macromolecules. In the present study, Western blot analysis indicated that the soluble form of beta-lyase, but not the mitochondrial form, was present in the epididymis and efferent ducts. Both forms of beta-lyase were detected in the kidney. When rats were dosed with DCVC, no protein adducts were detected in the epididymis or efferent ducts, although adducts were present in the proximal tubule of the kidney. Trichloroethylene can also be metabolized and form protein adducts through a cytochrome p450-mediated pathway. Western blot analysis detected the presence of cytochrome p450 2E1 (CYP2E1) in the efferent ducts. Immunoreactive proteins were localized to efferent duct and corpus epididymis epithelia. Metabolism of TCE was demonstrated in vitro using microsomes prepared from untreated rats. Metabolism was inhibited 77% when efferent duct microsomes were preincubated with an antibody to CYP2E1. Dichloroacetyl adducts were detected in epididymal and efferent duct microsomes exposed in vitro to TCE. Results from the present study indicate that the cytochrome p450-dependent formation of reactive intermediates and the subsequent covalent binding of cellular proteins may be involved in the male reproductive toxicity of TCE.

Ultrastructural localization of phosphoglycerate kinase in adult Clonorchis sinensis

Phosphoglycerate kinase (PGK) is an enzyme that produces one ATP molecule in the glycolytic pathway. Clonorchis sinensis is largely dependent on glycolysis for energy production. We performed immunoelectron microscopy on adult C. sinensis by using mouse immune serum raised against recombinant C. sinensis PGK. A high density of gold particles was found in the microvilli of the intestinal epithelium and in lamellae of the sperm duct. PGK was common in the somatic cells of intra-uterine eggs and in excreted products. It was localized with moderate intensity in muscular fibers of the subtegumental muscle layer, and in the myoepithelia of the intestine and excretory bladder. We suggest that PGK plays an essential role in C. sinensis energy production for movement via muscle contraction.

Localization of 11beta-hydroxysteroid dehydrogenase types 1 and 2 in the male reproductive tract

The action of glucocorticoids in target tissues is dependent on the local expression of glucocorticoid receptors and two 11beta-hydroxysteroid dehydrogenase (11beta-HSD) enzymes, 11beta-HSD1 and 11beta-HSD2, which interconvert active and inactive glucocorticoids. This study examined expression of the 11beta-HSD enzymes in the male reproductive tract of the adult rat. 11beta-HSD1 was immunolocalized to the apical region of principal epithelial cells of the caput epididymis, with the less numerous clear cells devoid of signal. Epididymal 11beta-HSD1 expression was confirmed by Western blot analysis, with immunoreactive species identified at 34 kDa (the expected size for 11beta-HSD1) and at approximately 48 kDa. 11beta-HSD bioactivity was readily detectable in the epididymis, with 11-oxoreductase activity clearly the favored reaction (as observed in liver), consistent with 11beta-HSD1 expression. The epithelium of the vas deferens, seminal vesicle, and penile urethra were also immunopositive for 11beta-HSD1, as were smooth muscle cells of the vas deferens and penile blood vessels. 11beta-HSD2 was also immunolocalized to the epididymal epithelium, but its distribution was complementary to that of 11beta-HSD1 (i.e. clear cells showing intense 11beta-HSD2 staining but principal cells devoid of signal). 11beta-HSD2 was also present in the corpora cavernosa of the penis but not in other tissues. In conclusion, the differential expression of 11beta-HSD1 and 11beta-HSD2 throughout the male reproductive tract suggests that these enzymes locally modulate glucocorticoid and mineralocorticoid actions, particularly in the epididymis and penile vasculature.

A role for protein kinase C in the supersensitivity of the rat vas deferens following chronic surgical denervation

Chronic surgical denervation of the rat vas deferens leads to an enhanced contractile response of the tissue to norepinephrine in vitro. Norepinephrine produces a higher rate of protein kinase C translocation to the particulate fraction of denervated tissues as compared with the paired, control vas deferens. Diacylglycerol generation in response to norepinephrine and contractile responses to phorbol diacetate were not altered by chronic denervation of the vas deferens. However, the contractile response to norepinephrine in these tissues was less susceptible to the inhibitory effects of the calcium channel blocker nifedipine. A potential role of protein kinase C in sensitizing the contractile apparatus to mobilized calcium in denervation supersensitivity is discussed.

Enzyme kinetics and pharmacological characterization of nucleotidases released from the guinea pig isolated vas deferens during nerve stimulation: evidence for a soluble ecto-nucleoside triphosphate diphosphohydrolase-like ATPase and a soluble ecto-5'-nucleotidase-like AMPase

Previously, we have demonstrated that stimulation of the sympathetic nerves of the guinea pig vas deferens evokes release not only of the cotransmitters ATP and norepinephrine but also of soluble nucleotidases that break down extracellular ATP, ADP, and AMP into adenosine. In this study we show that the apparent K(m) values of the releasable enzyme activity vary depending on which of these adenine nucleotides is used as initial substrate. The K(m) value for ATP was 33.6 +/- 2.3 microM, 21.0 +/- 2.3 microM for ADP, and 10.0 +/- 1.1 microM for AMP. The ratios of the V(max) values for each enzyme reaction were 4:2:3. We have also found a different sensitivity of the metabolism of ATP and AMP by releasable nucleotidases to known nucleotidase inhibitors. Suramin inhibited the breakdown of ATP by releasable nucleotidases in a noncompetitive manner and with a K(i) value of 53 microM, but had no effect on the breakdown of AMP. The 5'-nucleotidase inhibitor alpha,beta-methylene ADP inhibited the breakdown of AMP but not that of ATP. Concanavalin A inhibited the breakdown of AMP but had neither inhibitory nor facilitatory effects on the breakdown of ATP. 6-N,N-Diethyl-beta,gamma-dibromomethylene-D-ATP (ARL67156), an ecto-ATPase inhibitor, suppressed ATPase and AMPase activities, whereas NaN(3) (10 mM) affected neither reaction, but inhibited the ADP metabolism. Phosphatase- and phosphodiesterase inhibitors did not affect the activity of the releasable nucleotidases. This evidence suggests that the soluble nucleotidases released during neurogenic stimulation of the guinea pig vas deferens combine an ecto-5'-nucleotidase-like and an ecto-nucleoside triphosphate diphosphohydrolase-like activity.

Estrogen sulfotransferase: discrete and androgen-dependent expression in the male reproductive tract and demonstration of an in vivo function in the mouse epididymis

Estrogen sulfotransferase (EST) catalyzes the sulfoconjugation and inactivation of the steroid hormone estrogen. It is known previously that EST is expressed abundantly in Leydig cells of the testis. We recently have shown that male mice with targeted EST gene disruption developed age related Leydig cell and seminiferous tubule abnormalities as a consequence of increased local estrogen stimulation. In the same study, we also found that epididymal sperm isolated from the mutant mice had significantly reduced motility, but whether this reflected impaired epididymal function or was secondary to the testicular lesions was not known. The purpose of the current study was to investigate if EST is normally present in the mouse epididymis and/or other parts of the male reproductive tract where, as in testis, it may play a role in regulating local estrogen homeostasis. We describe here that EST is expressed in the epithelium of corpus and cauda but not caput regions of the mouse epididymis. It is also expressed in the luminal epithelium and smooth muscle cells of the vas deferens but was present at very low levels, if at all, in the prostate or seminal vesicle/ coagulating gland. Hypophysectomy, castration, and epididymal ligation experiments, together with the use of an androgen receptor antagonist, established that EST expression in the epididymis and vas deferens is critically dependent on pituitary hormone(s) and androgen but not on other factors in the testicular fluid. Administration of exogenous estradiol to mice with surgically ligated epididymis resulted in a more pronounced reduction in sperm motility in EST mutant mice than in wild-type mice. We conclude that EST is discretely expressed and regulated in the male reproductive tract and plays a physiological role in maintaining the functional integrity of the epididymis by regulating luminal estrogen homeostasis.

Role of sperm surface arylsulfatase A in mouse sperm-zona pellucida binding

We have previously described the zonae pellucidae (ZP) binding ability of a pig sperm surface protein, P68. Our recent results on peptide sequencing of 3 P68 tryptic peptides and molecular cloning of pig testis arylsulfatase A (AS-A) revealed the identity of P68 as AS-A. In this report, we demonstrate the presence of AS-A on the mouse sperm surface and its role in ZP binding. Using anti-AS-A antibody, we have shown by immunoblotting that AS-A was present in a Triton X-100 extract of mouse sperm. The presence of AS-A on the sperm plasma membrane was conclusively demonstrated by indirect immunofluorescence, immunogold electron microscopy, and AS-A's desulfation activity on live mouse sperm. The AS-A remained on the head surface of in vivo capacitated sperm, as revealed by positive immunofluorescent staining of oviductal/uterine sperm. Significantly, the role of mouse sperm surface AS-A on ZP binding was demonstrated by dose-dependent decreases of sperm-ZP binding on sperm pretreatment with anti-AS-A IgG/Fab. Furthermore, Alexa-430 conjugated AS-A bound to mouse ZP of unfertilized eggs but not to fertilized ones, and this level of binding increased and approached saturation with increasing Alexa-430 AS-A concentrations. Moreover, in vivo fertilization was markedly decreased when mouse sperm pretreated with anti-AS-A IgG were artificially inseminated into females. All of these results designated a new function for AS-A in mouse gamete interaction.

Localization of a proteolytic enzyme within the efferent and deferent duct epithelial cells of the turkey (Meleagris gallopavo) using immunohistochemistry

Turkey seminal plasma contains a serine protease found to be distinct from the spermatozoal acrosin. However, the origin and biological roles of this enzyme are unknown. Our experimental objective was to identify the cellular source of this protease within the male reproductive tract. The enzyme was isolated from seminal plasma using benzamidine-Sepharose 6B chromatography. A synthetic substrate, Nalpha-benzoyl-DL-arginine p-nitroanilide, was used to detect fractions containing the enzyme. The affinity chromatography technique yielded a 150-fold increase in amidase activity. Analysis of the protease by SDS-PAGE revealed two protein bands with relative molecular masses of 37 000 and 61 000. Proteolytic activity was detected within the smaller band as evidenced by casein digestion. Further analysis of the purified protein revealed that the smaller protein band was glycosylated. To determine the cellular source of the protease, a panel of mouse monoclonal antibodies was then developed against the purified protease, and used in immunohistochemistry. Frozen tissue sections from the liver, testis, epididymal region, and deferent duct were fixed in 4% (w/v) paraformaldehyde, permeabilized with 0.2% (v/v) (octylphenoxy)polyethoxyethanol followed by routine immunohistochemistry procedures. Monoclonal antibodies did not bind to tissue sections from either the liver or testis, or to blood plasma proteins. Both the distal portion of the efferent duct and the deferent duct were immunoreactive. We concluded that the protease found in turkey seminal plasma is concentrated to the distal efferent duct and the deferent duct epithelial cells.

Urodilatin attenuates sympathetic neurotransmission in the rabbit isolated vas deferens without activating guanylyl cyclase

Natriuretic peptides are produced in cardiovascular, renal and neural tissues and are believed to reduce arterial blood pressure by augmenting sodium and water loss in the urine. Another potential antihypertensive action of these peptides involves a suppression of adrenergic neurotransmission. Atrial, brain and C-type natriuretic peptides suppress sympathetic neurotransmission but no data are available on neuromodulatory actions of urodilatin. This study investigates the hypothesis that urodilatin and brain natriuretic peptide inhibit sympathetic neurotransmission by elevating guanylyl cyclase activity. Both brain natriuretic peptide and urodilatin suppressed force generation in response to electrical stimulation of the vas deferens. Brain natriuretic peptide accelerated the production of cyclic guanosine monophosphate equipotently with its effects on neurotransmission. However, urodilatin failed to increase guanylyl cyclase activity, thus dissociating its effects on neurotransmission from guanylyl cyclase stimulation. None of the natriuretic peptides altered contractile effects of either adenosine triphosphate or norepinephrine, the two putative neurotransmitters secreted from adrenergic nerves in the vas deferens. These data are consistent with the following conclusions: 1) all of the known endogenous natriuretic peptides suppress adrenergic neurotransmission; 2) guanylyl cyclase activation is not required for the inhibition of sympathetic neurotransmission by natriuretic peptides; and 3) inhibitory effects of the natriuretic peptides on neurotransmission result from a suppression of neurotransmitter exocytosis. The novel findings of this study include both the suppression of sympathetic neurotransmission by urodilatin and its biological activity in the absence of guanylyl cyclase activation.

Sperm disposal system in spermatic granuloma: a link with superoxide radicals

Spermatic granulomas are believed to maintain "physiological harmony" in the male reproductive tract by maintaining a balance of hydrostatic pressure post-vasectomy. The mechanism for the disposal of deposited spermatozoa in the granuloma core is not clear. A fourfold rise in the production of superoxide along with ascorbyl and dienyl radicals and a 50% drop in the production of nitric oxide (NO) radicals by granuloma tissue hints that a reaction between NO and superoxide radicals could lead to the formation of peroxynitrite species which may contribute to the disposal of spermatozoa in the granuloma core. A higher protease activity and low hypoxanthine content in the granuloma indicates that a free radical driven sperm disposal system is active in granulomas.

Expression of CPI-17 and myosin phosphatase correlates with Ca(2+) sensitivity of protein kinase C-induced contraction in rabbit smooth muscle

1. Various smooth muscles have unique contractile characteristics, such as the degree of Ca(2+) sensitivity induced by physiological and pharmacological agents. Here we evaluated six different rabbit smooth muscle tissues for protein kinase C (PKC)-induced Ca(2+) sensitization. We also examined the expression levels of myosin light chain phosphatase (MLCP), the MLCP inhibitor phosphoprotein CPI-17, and the thin filament regulator h-calponin. 2. Immunohistochemical and Western blot analyses indicated that CPI-17 was found primarily in smooth muscle, although expression varied among different tissues. Vascular muscles contained more CPI-17 than visceral muscles, with further distinction existing between tonic and phasic subtypes. For example, the tonic femoral artery possessed approximately 8 times the cellular CPI-17 concentration of the phasic vas deferens. 3. In contrast to CPI-17 expression patterns, phasic muscles contained more MLCP myosin-targeting subunit than tonic tissues. Calponin expression was not statistically different. 4. Addition of phorbol ester to alpha-toxin-permeabilized smooth muscle caused an increase in contraction and phosphorylation of both CPI-17 and myosin light chain (MLC) at submaximal [Ca(2+)]i. These responses were several-fold greater in femoral artery as compared to vas deferens. 5. We conclude that the expression ratio of CPI-17 to MLCP correlates with the Ca(2+) sensitivities of contraction induced by a PKC activator. PKC stimulation of arterial smooth muscle with a high CPI-17 and low MLCP expression generated greater force and MLC phosphorylation than stimulation of visceral muscle with a relatively low CPI-17 and high MLCP content. This implicates CPI-17 inhibition of MLCP as an important component in modulating vascular muscle tone.

Distribution of the vacuolar H+ atpase along the rat and human male reproductive tract

Luminal acidification in parts of the male reproductive tract generates an appropriate pH environment in which spermatozoa mature and are stored. The cellular mechanisms of proton (H+) secretion in the epididymis and the proximal vas deferens involve the activity of an apical vacuolar H+ ATPase in specialized cell types, as well as an apical Na+/H+ exchanger in some tubule segments. In this study we used Western blotting and immunocytochemistry to localize the H+ ATPase in various segments of the male reproductive tract in rat and man as a first step toward a more complete understanding of luminal acidification processes in this complex system of tissues. Immunoblotting of isolated total cell membranes indicated a variable amount of H+ ATPase in various segments of the rat reproductive tract. In addition to its known expression in distinct cell types in the epididymis and vas deferens, the H+ ATPase was also localized at the apical pole and in the cytoplasm of epithelial cells in the efferent duct (nonciliated cells), the ampulla of the vas deferens and the ventral prostate (scattered individual cells), the dorsal and lateral prostate, the ampullary gland, the coagulating gland, and all epithelial cells of the prostatic and penile urethra. Both apical and basolateral localization of the protein were found in epithelial cells of the prostatic ducts in the lateral prostate and in periurethral tissue. Only cytoplasmic, mostly perinuclear localization of the H+ ATPase was found in all epithelial cells of the seminal vesicles and in most cells of the ventral prostate and coagulating gland. No staining was detected in the seminiferous tubules, rete testis, and bulbourethral gland. In human tissue, H+ ATPase-rich cells were detected in the epididymis, prostate, and prostatic urethra. We conclude that the vacuolar H+ ATPase is highly expressed in epithelial cells of most segments of the male reproductive tract in rat and man, where it may be involved in H+ secretion and/or intracellular processing of the material endocytosed from the luminal fluid or destined to be secreted by exocytosis.

Expression of the transmembrane carbonic anhydrases, CA IX and CA XII, in the human male excurrent ducts

Testicular fluid is concentrated and acidified during its passage through the excurrent ducts. These processes involve bicarbonate absorption, in which carbonic anhydrases are implicated. In this study, the distribution of two transmembrane carbonic anhydrase isozymes (CA IX and CA XII) in the human excurrent ducts was investigated using isozyme-specific antibodies in conjunction with immunohistochemical and immunoblotting techniques. Specific staining for CA XII was present in the basolateral plasma membrane of the epithelial cells in the efferent ducts, predominantly in the non-ciliated cells. In the epididymal duct, CA XII was detected only in sporadic cells, which also contained CA II, thus suggesting that they are apical mitochondria-rich cells. CA IX was also localized to the basolateral plasma membrane of the epithelium in the efferent ducts, but its staining was weaker and less uniform compared to CA XII. No signal for CA IX was detected in the epididymal duct. Western blot analysis from efferent duct samples revealed specific bands for CA IX and CA XII, confirming that the immunohistochemical stainings represent these isozymes. The expression of CA XII and CA IX in the excurrent duct system and co-expression of CA XII with Aquaporin-1 in the same efferent duct epithelial cells suggest their functional involvement in ion transport and concentration processes of testicular fluid.

The cellular physiology of carbonic anhydrases

Carbonic anhydrases are zinc metalloenzymes that catalyze the reversible hydration of CO(2) to form HCO(3)(-) and protons according to the following reaction: CO(2) + H(2)O <=> H(2)CO(3) <=> HCO(3)(-) + H(+). The first reaction is catalyzed by carbonic anhydrase and the second reaction occurs instantaneously. The carbonic anhydrase (CA) gene family includes ten enzymatically active members, which are major players in many physiological processes, including renal and male reproductive tract acidification, bone resorption, respiration, gluconeogenesis, signal transduction, and formation of gastric acid. The newly identified CA IX (previously called MN) and CA XII are related to cell proliferation and oncogenesis. Carbonic anhydrase isozymes have different kinetic properties and they are present in various tissues and in various cell compartments. CA I, II, III and VII are cytoplasmic, CA V is mitochondrial, and CA VI is present in salivary secretions. CA IV, IX, XII and XIV are membrane proteins: CA IV is a glycosyl-phosphatidylinositol-anchored protein, and CA IX, XII and XIV are transmembrane proteins. The present work will focus on the roles of CA II and CA IV in transepithelial proton secretion and bicarbonate reabsorption processes. The localization of these isoforms in selected epithelia that are involved in net acid/base transport, such as kidney proximal tubules and collecting ducts, and tubules from the male reproductive tract will be reviewed.

Constant expression of cyclooxygenase-2 gene in prostate and the lower urinary tract of estrogen-treated male rats

Expression of cyclooxygenase-2 (E. C. 1.14.99.1) in prostate and the lower urinary tract (LUT) of the neonatally estrogenized male rat has been studied by using a COX-2's PCR fragment of 724 nt spanning 3 introns and a 478nt internal standard for quantitative RT-PCR. The same fragment of 724 nt was used for RNA probe in Northern hybridization. Neonatal estrogenization (10 microg/day of diethylstilbestrol on days 1-5) had no effect on COX-2 expression in prostatic urethra, prostatic lobes, or bladder. Acute estrogen treatment of castrated animals did not induce COX-2 expression, either. In addition the differential expression of basal level of COX-2 in the different lobes of prostate in normal rat was demonstrated. Our results suggest a constant expression of COX-2 gene in prostate and the lower urinary tract of the neonatally estrogenized (neoDES) rats. The present study indicates that the increased expression of COX-2 is probably not essential for the estrogen-driven development of stromal inflammation or hyperplastic and dysplastic alterations in the prostate of neoDES rats.

Expression and regulation of H+K+ATPase in lysosomes of epithelial cells of the adult rat epididymis

Endocytosis is an important event in the epididymis as it contributes to a luminal environment conducive for sperm maturation. Principal and clear cells contain numerous lysosomes which degrade many substances internalized by endocytosis from the epididymal lumen. The interior of the lysosomes depends on low pH to activate the release of their enzymes and to activate their acid hydrolases. In the present study, H+K+ATPase was localized by light microscopy in the adult rat epididymis of intact and of orchidectomized animals supplemented with testosterone or not. In normal animals, numerous lysosomes of nonciliated cells of the efferent ducts were intensely reactive for anti-H+K+ATPase antibody. In the initial segment, only a few lysosomes of principal cells were reactive. In the intermediate zone of the epididymis, numerous lysosomes of principal cells were intensely reactive, while the number of intensely reactive lysosomes decreased progressively from the proximal caput to the distal caput with none being seen in the proximal corpus region. In the distal corpus and cauda regions, only a few lysosomes of some principal cells were reactive. In contrast, clear cells of all regions showed intense reactivity. Orchidectomy resulted in the abolishion of H+K+ATPase in lysosomes of principal cells of all regions except the initial segment. However, while clear cells of the caput and corpus regions also became unreactive, those of the cauda region remained as reactive as in controls. Orchidectomized animals supplemented with testosterone maintained a staining pattern similar to controls for both cell types. These observations demonstrate the presence in principal and clear cells of H+K+ ATPase which may have an important role in acidifying the interior of their lysosomes. However, there is a region-specific expression of H+K+ATPase in lysosomes of principal cells, unlike that for clear cells. In addition, H+K+ATPase expression in lysosomes of principal cells depends on testosterone in all regions except the initial segment. However, in the case of clear cells, only those of the caput and the corpus regions are dependent on testosterone, while those of the cauda region appear to be regulated by some other factor.

Physiological functions and hormonal regulation of mouse vas deferens protein (AKR1B7) in steroidogenic tissues

The MVDP (mouse vas deferens protein) gene encodes an aldose reductase-like protein (AKR1B7) highly expressed in vas deferens epithelium and zona fasciculata of the adrenal cortex. Recombinant MVDP showed kinetic properties distinct from those of aldose reductase, including its spectrum of substrates, cofactor preference and sensitivity to inhibitors. We demonstrate that in adrenocortical cells, MVDP, rather than aldose reductase, is the principal reductase for isocaproaldehyde (a product of side-chain cleavage of cholesterol) and 4-hydroxynonenal (a lipid peroxidation product). In steroidogenic tissues MVDP expression is regulated by pituitary trophic hormones, namely ACTH in adrenals, FSH in ovaries, and LH in testicular Leydig cells.

Correlation between the release of the sympathetic neurotransmitter ATP and soluble nucleotidases from the guinea pig vas deferens

Recently, we have shown that by releasing specific nucleotidases the sympathetic nerves of the guinea pig vas deferens may regulate the metabolism of extracellular adenine nucleotides and consequently, the inactivation of neurotransmitter ATP. Based on the evidence for tetrodotoxin sensitivity and calcium dependence of the nerve stimulation-evoked overflow of enzyme activity, we have suggested that soluble nucleotidases may be stored in synaptic vesicles within the sympathetic nerves and released upon arrival of nerve action potentials by a mechanism similar to that for release of neurotransmitters. To further test this hypothesis we studied the time course of nerve stimulation-evoked overflow of ATP, norepinephrine (NE), releasable ATPase (r-ATPase) activity, and releasable AMPase (r-AMPase) activity under control conditions and in the presence of drugs known to selectively modulate sympathetic neurotransmission. The results show that the time course of overflow of r-ATPase and r-AMPase activities resembles the transient pattern of overflow of ATP but not the tonic pattern of overflow of NE. Vasa deferentia dissected from animals treated with reserpine release ATP, r-ATPase, and r-AMPase, whereas the overflow of NE is completely abolished. Guanethidine, on the other hand, inhibits equally well the overflow of the two neurotransmitters and the releasable nucleotidase activities. Agonists of the alpha(2)-adrenergic receptors abolish the overflow of ATP, r- ATPase, and r-AMPase but not the overflow of NE. This evidence supports the idea that the sympathetic nerves of the guinea pig vas deferens store and release ATP together with specific nucleotidases responsible for the inactivation of this neurotransmitter.

Expression of the lipocalin-type prostaglandin D synthase gene in the reproductive tracts of Holstein bulls

The aim of this study was to localize expression of the prostaglandin D synthase gene in the reproductive tracts of Holstein bulls using northern blotting and in situ hybridization. For northern blotting, a digoxigenin-labelled prostaglandin D synthase cDNA probe was used to probe blots containing RNA isolated from the testes, epididymides, vas deferens, ampullae, seminal vesicles, prostate and bulbourethral glands of bulls. The digoxigenin-labelled cDNA for the bovine homologue of prostaglandin D synthase hybridized to a single band (approximately 0.9 kb) to RNA samples from the caput, corpus and cauda epididymides, as well as RNA samples from the vas deferens and the ampulla. The probe also detected a single band in testis samples, although the transcript size was slightly larger (approximately 1.0 kb) than the transcript found in the other tissues. The highest expression of prostaglandin D synthase was observed in the testes and caput epididymides. Prostaglandin D synthase transcripts were not found in the seminal vesicles or the prostate or bulbourethral glands using northern blotting. For in situ hybridization, antisense and sense riboprobes were synthesized and used to hybridize to cryosections obtained from the reproductive tissues of bulls. In situ hybridization of bull testes showed that prostaglandin D synthase transcripts were present within the germ cells in the adluminal compartment of the seminiferous tubules containing round and elongated spermatids, indicating that expression varied with stage of development of the seminiferous tubules. Prostaglandin D synthase expression was observed in the epithelial cells of the epididymides with greatest expression occurring in the caput epididymidis. Some expression was also observed in the epithelial cells of the vas deferens and a few cells of some lobules in the prostate and bulbourethral glands. Expression of the prostaglandin D synthase gene was not detected in ampullae or seminal vesicles by in situ hybridization.

Release of a soluble ATPase from the rabbit isolated vas deferens during nerve stimulation

The properties of the ATPase released during electrical field stimulation (EFS) (8 Hz, 25 s) of the sympathetic nerves of the superfused rabbit isolated vas deferens were investigated. Superfusate collected during EFS rapidly metabolised exogenous ATP (100 microM) and 50% was broken down in 5.67+/-0.65 min. The main metabolite was ADP, virtually no AMP was produced and adenosine was absent. No enzyme activity was seen in samples collected in the absence of EFS. Lineweaver-Burke analysis of the initial rates of ATP hydrolysis gave a K(M) of 40 microM and V(max) of 20.3 nmol ATP metabolized min(-1) ml(-1) superfusate. ATPase activity was unaffected by storage at room temperature for 24 h, but was abolished at pH4 or by heating at 80 degrees C for 10 min. ARL 67156 inhibited ATP breakdown in a concentration-dependent manner (IC(50)=25 microM (95% confidence limits=22-27 microM), Hill slope=-1.06+/-0.04). When EFS was applied three times at 30 min intervals, ATP metabolism was 20-30% less in superfusate collected during the second and third stimulation periods compared with the first. ATPase activity was released in a frequency-dependent manner, with significantly greater activity seen after stimulation at 4 and 8 Hz than at 2 Hz. In conclusion, EFS of the sympathetic nerves in the rabbit vas deferens causes release of substantial ATPase, but little ADPase activity into the extracellular space. This contrasts with the guinea-pig vas deferens, which releases enzymes that degrade ATP to adenosine. Thus, the complement of enzymes released by nerve stimulation is species-dependent.

Down-regulation of Na(+)/K(+)-ATPase alpha(2) isoform in denervated rat vas deferens

In the rat vas deferens, an organ richly innervated by peripheral sympathetic neurons, we have demonstrated recently the expression of alpha(1) and alpha(2), but not alpha(3) isoforms of the alpha subunit of Na(+)/K(+)-ATPase (EC 3.6.1.37), a membrane-bound enzyme of vital function for living cells (Noël et al., Biochem Pharmacol 55: 1531-1535, 1998). In the present work, we characterized, qualitatively and quantitatively, Na(+)/K(+)-ATPase alpha isoforms in denervated rat vasa deferentia. [(3)H]Ouabain binding at concentrations defined for high-affinity isoforms (alpha(2) and/or alpha(3)) detected only one class of specific binding sites in control (C) and denervated (D) vas deferens. Although the dissociation constant was similar for both groups [K(d) = 138 +/- 14 nM (C) and 125 +/- 8 nM (D)], a marked decrease in density was observed after denervation [716 +/- 81 fmol.mg protein(-1) (C) and 445 +/- 34 fmol.mg protein(-1) (D), P < 0.05]. In addition, western blotting revealed that denervated vasa deferentia produce the alpha(1) and alpha(2) isoforms but not alpha(3), just as we reported for the controls previously (Noël et al., Biochem Pharmacol 55: 1531-1535, 1998). Densitometric analysis showed a decrease of the alpha(2) isoform by about 40% in denervated organs, in very good agreement with what was shown with the [(3)H]ouabain binding technique, but no significant change in alpha(1) isoform density. Truncated alpha(1) (alpha(1)T), an isoform suggested to exist in the guinea pig vas deferens, was not detected. Altogether, our results demonstrated that Na(+)/K(+)-ATPase alpha(2) is down-regulated after sympathetic denervation of the rat vas deferens.

Characterization of the ATPase released during sympathetic nerve stimulation of the guinea-pig isolated vas deferens

The release of ATPase activity evoked by electrical field stimulation (EFS) (8 Hz, 25 s) was investigated in several tissues in which adenosine 5'-triphosphate (ATP) acts as a neurotransmitter. Superfusate collected during EFS of sympathetic nerves of the guinea-pig, rat and mouse isolated vas deferens and parasympathetic nerves of the guinea-pig isolated urinary bladder contained ATPase activity. ATP breakdown was fastest in superfusate collected from the guinea-pig isolated vas deferens. However, EFS of the enteric nerves of the guinea-pig isolated taenia coli did not release any detectable ATPase. The ATPase released from the guinea-pig isolated vas deferens metabolized ATP at similar rates at incubation temperatures of 37 degrees C and 20 degrees C. Lineweaver-Burke analysis of the initial rates of ATP hydrolysis gave a K(M) of 39 microM and a V(max) of 1039 pmol ATP metabolized min(-1) ml(-1) superfusate. 6-N,N-diethyl-D-beta,gamma-dibromomethyleneATP (ARL 67156), pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) and pyridoxal-5'-phosphate (P-5-P) all inhibited the ATPase activity in a concentration-dependent manner with a potency order of ARL 67156 = PPADS>P-5-P. In conclusion, EFS of several tissues in which ATP is a neurotransmitter causes the release of an ATPase and activity is greatest in the guinea-pig vas deferens. The enzyme has pharmacological and kinetic characteristics that are similar to ectonucleoside triphosphate diphosphohydrolases.

H(+)V-ATPase-dependent luminal acidification in the kidney collecting duct and the epididymis/vas deferens: vesicle recycling and transcytotic pathways

Many vertebrate transporting epithelia contain characteristic ‘mitochondria-rich’ cells that express high levels of a vacuolar proton-pumping ATPase (H(+)V-ATPase) on their plasma membrane and on intracellular vesicles. In the kidney cortex, A-cells and B-cells are involved in proton secretion and bicarbonate secretion, respectively, in the distal nephron and collecting duct. A-cells have an H(+)V-ATPase on their apical plasma membrane and on intracellular vesicles, whereas the cellular location of the H(+)V-ATPase can be apical, basolateral, bipolar or diffuse in B-cells. The rat epididymis and vas deferens also contain a distinct population of H(+)V-ATPase-rich epithelial cells. These cells are involved in generating a low luminal pH, which is involved in sperm maturation and in maintaining sperm in an immotile state during their passage through the epididymis and vas deferens. In both kidney and reproductive tract, H(+)V-ATPase-rich cells have a high rate of apical membrane recycling. H(+)V-ATPase molecules are transported between the cell surface and the cytoplasm in vesicles that have a well-defined ‘coat’ structure formed of the peripheral V(1) subunits of the H(+)V-ATPase. In addition, we propose that B-type intercalated cells have a transcytotic pathway that enables them to shuttle H(+)V-ATPase molecules from apical to basolateral plasma membrane domains. This hypothesis is supported by data showing that A-cells and B-cells have different intracellular trafficking pathways for LGP120, a lysosomal glycoprotein. LGP120 was found both on the basolateral plasma membrane and in lysosomes in B-cells, whereas no LGP120 was detectable in the plasma membrane of A-cells. We propose that the ‘polarity reversal’ of the H(+)V-ATPase in B-intercalated cells is mediated by a physiologically regulated transcytotic pathway that may be similar to that existing in some other cell types.

Comparative localization of heme oxygenase-2 and nitric oxide synthase in the autonomic innervation to the human ductus deferens and seminal vesicle

PURPOSE

The aim of present study was to determine the topographic relationship between heme oxygenase-2 (HO-2), which synthesizes carbon monoxide (CO), and neuronal nitric oxide synthase (nNOS), which generates nitric oxide (NO), in the autonomic nerves of the human ductus deferens and seminal vesicle.

MATERIALS AND METHODS

Specimens of the ductus deferens and seminal vesicle were obtained during cancer surgery or vasectomy. HO-2 and nNOS were localized by indirect immunofluorescence. Additionally, the histochemical NADPH-diaphorase (NADPH-d) activity of NOS was demonstrated using a standard staining method and some modifications.

RESULTS

Anti-HO-2 labeling stained virtually all nerve cell bodies in local ganglia of the pelvic plexus, which is composed of a mixed population of postganglionic sympathetic and parasympathetic neurons supplying the pelvic viscera. Furthermore, nerve cell bodies in the wall of the seminal vesicle, which are considered an extension of the pelvic plexus, were also found to stain positively for HO-2. Some of the HO-2-immunoreactive ganglion cells were also nNOS-positive, their proportion varying between individual ganglia but generally not exceeding 20%. Both enzymes were present in large adventitial nerve trunks. Only nNOS but no HO-2 was found in small intramuscular and mucosal nerve fibers. In both the ductus deferens and seminal vesicle, the highest density of nNOS-containing nerve fibers was in the lamina propria of the mucosa. A well-developed plexus of nNOS-positive nerve fibers was also observed in the muscular layer of the seminal vesicle. By contrast, there was a very sparse innervation by nNOS-positive nerve fibers in the muscle coat of the ductus deferens. In addition, a population of epithelial cells in the seminal vesicle may contain an isoform of NOS, as revealed by a resistant NADPH-d activity.

CONCLUSIONS

These findings set the scene for functional studies which will hopefully clarify the biological role of CO and NO in the control of the ductus deferens and seminal vesicle.

Product of side-chain cleavage of cholesterol, isocaproaldehyde, is an endogenous specific substrate of mouse vas deferens protein, an aldose reductase-like protein in adrenocortical cells

Mouse vas deferens protein (MVDP) is an aldose reductase-like protein that is highly expressed in the vas deferens and adrenal glands and whose physiological functions were unknown. We hereby describe the enzymatic characteristics of MVDP and its role in murine adrenocortical Y1 cells. The murine aldose reductase (AR) and MVDP cDNAs were expressed in bacteria to obtain recombinant proteins and to compare their enzymatic activities. Recombinant MVDP was functional and displayed kinetic properties distinct from those of murine AR toward various substrates, a preference for NADH, and insensitivity to AR inhibitors. For MVDP, isocaproaldehyde, a product of side-chain cleavage of cholesterol generated during steroidogenesis, is the best natural substrate identified so far. In Y1 cells, we found that NADH-linked isocaproaldehyde reductase (ICR) activity was much higher than NADPH-linked ICR activity and was not abolished by AR inhibitors. We demonstrate that in Y1 cells, forskolin-induced MVDP expression enhanced NADH-linked ICR activity by 5-6-fold, whereas no variation in ICR-linked NADPH activity was observed in the same experiment. In cells stably transfected with MVDP antisense cDNA, NADH-linked ICR activity was abolished even in the presence of forskolin, and the isocaproaldehyde toxicity was increased compared with that of intact Y1 cells, as measured by isocaproaldehyde LD(50). In Y1 cells transfected with MVDP antisense cDNA, forskolin-induced toxicity was abolished by aminoglutethimide. These results indicate that in adrenocortical cells, MVDP is responsible for detoxifying isocaproaldehyde generated by steroidogenesis.

Immunocytochemical localization of the Ya, Yb1, Yc, Yf, and Yo subunits of glutathione S-transferases in the cauda epididymidis and vas deferens of adult rats

Glutathione S-transferases (GSTs) are dimeric proteins grouped into five classes based on the degree of amino acid homology of their subunits. They are involved in cellular detoxification through the catalyzation of the conjugation of reduced glutathione with various electrophilic substances. In the present study, the distribution of Ya and Yc subunits from the alpha family, Yb1 and Yo subunits of the mu class, and the Yf subunit of the pi class were examined with light microscope immunocytochemistry in Bouin-fixed, paraffin-embedded tissue of different regions of the cauda epididymidis and vas deferens. In the cauda, principal cells showed high levels of expression of Ya, Yc, and Yo subunits, while in the vas deferens, staining decreased to moderate levels for the Ya and Yo subunits and to low levels for the Yc subunit. While Yf was maintained at low levels in principal cells of all cauda and vas deferens regions, Yb1 expression was more erratic, presenting a checkerboard-like staining pattern in the proximal vas deferens and showing moderate cytoplasmic but intense nuclear reactivity in all other regions. Basal cells in the cauda were intensely reactive for Yf, while in the vas deferens, they became unreactive. Conversely, basal cells were unreactive for Ya in the cauda and proximal vas deferens, while in the middle and distal vas deferens, they became moderately reactive. In the case of Yb1 and Yo, some basal cells were reactive while others appeared unreactive in all cauda and vas deferens regions. Yc elicited the display of both reactive and unreactive basal cells in the cauda regions, and while the cells were moderately reactive in the proximal vas deferens, they became intensely reactive in the middle and distal vas deferens. In summary, both principal and basal cells show varying degrees of GST expression in the different regions of the cauda and vas deferens, suggesting that these cells are subjected to a complex, changing environment of substrates. Furthermore, while expression often differs from principal to basal cells, the absence of reactivity of a given GST in one cell type is usually compensated for by expression in the other cell type in any given region of the cauda or vas deferens. Taken together, the data suggest that ample protection from harmful circulating electrophiles can be provided for sperm during their storage in the cauda and vas deferens. In addition, since principal cells of the vas deferens are involved in steroid synthesis, the presence of GSTs in these cells may also serve to bind steroids, or this presence may be involved in steroid isomerization.

Exogenous 17beta-estradiol blocks alpha and mu but not pi class glutathione S-transferase immunoreactivity in epithelium of Syrian hamster vas deferens

Members of the glutathione S-transferase (GST) family of detoxification enzymes play a role in chemotherapy resistance in certain cancers but have not been directly implicated as agents whose absence may predispose tissues to hormonally induced tumorigenesis. Here we report the development of a polyclonal antiserum to a hamster mu class GST, and immunohistochemical analysis of alpha, mu, and pi class GSTs to study the effects of hormone treatment on their expression in reproductive tract tissues of male golden Syrian hamsters. These animals develop leiomyosarcomas in the vas deferens after treatment with testosterone propionate (TP) and 17beta-estradiol (E2). High levels of all three GST classes were detected throughout the reproductive tract epithelium of control animals. In 100% of the experimental animals, 4 weeks of treatment either with E2 alone, or with E2 plus TP promoted a complete loss of immunostaining for alpha and mu class GSTs, but not for pi class GSTs, only in the epithelial lining of the vas deferens. In contrast, treatment with TP alone resulted in moderate hyperplasia of smooth muscle in the proximal vas deferens, with no cellular atypia and no changes in immunoreactivity of any of the GST classes. The consistent and site-specific nature of these results strongly suggests a functional role for GSTs in hormonally induced carcinogenic process. (J Histochem Cytochem 47:91-98, 1999)

Principal cells of the vas deferens are involved in water transport and steroid synthesis in the adult rat

Principal cells show marked structural differences in the proximal, middle, and distal regions of the vas deferens, reflective of diverse functional activities. In the present study, we performed electron microscopy to examine the structural features of principal cells using glutaraldehyde-fixed, Epon-embedded material, while functional parameters were examined using light microscopic immunocytochemistry on Bouin-fixed, paraffin-embedded material. In the proximal region, the cuboidal principal cells resembled those of the cauda epididymidis, but few clear cells and occasional narrow cells were present. In the middle region, principal cells often contained blebs of their apical cytoplasm containing vesicular and tubular profiles. These blebs extended far from the cell surface and appeared to be liberated into the lumen, suggesting an apocrine type of secretion. In the distal region, dilated intercellular spaces containing numerous membranous profiles of different shapes and sizes were noted between adjacent principal cells and overlying basal cells. The use of an anti-aquaporin-1 antibody revealed an intense reaction over the endothelial cells of numerous vascular channels in the lamina propria. Taken together, these observations suggested water transport from the lumen of the vas deferens via the dilated spaces to underlying vascular channels, the function of which may be to concentrate sperm. The infranuclear cytoplasm of principal cells of this region showed whorls of smooth endoplasmic reticulum (sER). Large intracytoplasmic cavities were found within the sER aggregates, and these contained membranous profiles that appeared to peel off from the surrounding sER elements. Various images of such cavities closely juxtaposed to the lateral plasma membrane suggested that the membranous profiles of the intercellular spaces were derived from them. Use of anti-3beta-hydroxysteroid dehydrogenase antibody revealed an intense reaction over principal cells of the vas deferens, as well as over the blebs in the lumen of the vas deferens, which is indicative of the steroid synthesis performed by these cells. The release of sER membranous profiles into the dilated spaces and the presence of blebs in the lumen may represent a means of transporting steroids that are destined for different sites out of the principal cells. Steroids in the blebs would be ultimately destined for utilization by luminal sperm, while those steroids in the dilated spaces are designed for utilization by muscle layers of the lamina propria. In summary, principal cells of the vas deferens appear to be involved in synthesis and secretion of steroids and in eliminating water from the lumen of the vas deferens.

GPx3: the plasma-type glutathione peroxidase is expressed under androgenic control in the mouse epididymis and vas deferens

We report here-using northern experiments, western blotting, and immunohistochemistry-on the findings that the plasma type glutathione peroxidase, GPx3, a major enzyme in reducing lipid hydroperoxides and hydrogen peroxide in plasma, is also expressed at significant levels in tissues of the male genital tract including epididymis and vas deferens. Within the epididymis and the kidney, the accumulation of the GPx3 mRNA and protein were investigated during postnatal development and found to be temporally regulated in a tissue-specific manner. Furthermore, we show here that androgen withdrawal by castration down regulates the expression of the GPx3 gene both in the epididymis and vas deferens while GPx3 expression in the kidney was found to be androgen-independent. Finally, immunohistochemistry data reveals that within the epididymis GPx3 distribution is quite peculiar suggesting the existence in this organ of complex traductional and/or transcriptional regulatory processes.

NADPH-diaphorase in glandular cells and nerves and its relation to acetylcholinesterase-positive nerves in the male reproductive tract of man and guinea-pig

The presence of NADPH-diaphorase activity and acetylcholinesterase in the testis, epididymis, vas deferens, seminal vesicle, pelvic plexus, prostate and urethra of man and guinea-pig was investigated with the nitro blue NADPH technique and the thiocholine method, respectively. In human material NADPH-diaphorase activity was found in the Leydig cells, Sertoli cells and the epithelial linings of the rete testis, the excretory ducts, seminal vesicle, prostate and urethra. The guinea-pig material showed staining of the Leydig cells and spermatozoa and similar epithelial staining of the tract as man. Nerves beneath the epithelium and in the muscle layers of cauda epididymis, vas deferens, seminal vesicle, prostate and urethra were also stained. NADPH-diaphorase-positive nerve cells were seen in the pelvic plexus. Some cells also displayed acetylcholinesterase activity but others showed activity for only one of the enzymes or no activity for either enzyme. In the cauda epididymis, vas deferens, seminal vesicle, prostate and urethra acetylcholinesterase-positive nerve fibres formed a plexus beneath the secretory cells. It is concluded that NADPH-diaphorase, generally accepted as a nitric oxide synthase, is present in glandular cells of the male genital tract. The enzyme is also present in nerves, where it is partly co-localized with acetylcholinesterase.

Constitutive expression of cyclooxygenase-2 in rat vas deferens

Prostaglandins, lipoid substances discovered in human semen as modulators of uterine muscle contractility, are known to play significant roles in virtually all mammalian organ systems, but their male reproductive functions are unclear. Cyclooxygenase, the rate-limiting enzyme in prostaglandin synthesis, occurs in two isoforms distinguished on the basis of constitutive (COX-1) or inducible (COX-2) expression patterns in mammalian tissues. However, in the adult rat male reproductive system, immunohistochemistry and Western and Northern analysis showed that COX-2 is the predominant isoform and is heavily localized to the epithelium of the distal vas deferens, where constitutive expression is manyfold greater than in any other organs of the body. COX-2 is not detected in the proximal one-half of the vas nor in the testis, epididymis, seminal vesicles, or prostate. Elimination of luminal sperm by vasectomy does not affect COX-2 levels, whereas castration severely depletes COX-2 and androgen replacement after castration restores COX-2, indicating that COX-2 expression in the vas is androgen dependent. Because the distal vas also comprises an extensive submucosal venous plexus connected to the penile corpora cavernosa, prostaglandins from the vas may play a role in erection.

Creatine synthesis and transport systems in the male rat reproductive tract

Previous studies from this laboratory showed that high levels of guanidinoacetate methyltransferase are present in mouse testis and epididymis, whereas guanidinoacetate methyltransferase mRNA and protein are not detected in seminal vesicles where large amounts of creatine (Cr) and phosphocreatine are found (Lee et al., Biol Reprod 1994; 50:152-162). To further investigate the origin(s) of Cr in the male reproductive tract, the expression patterns of the three enzymes and a transporter involved in Cr metabolism were examined with rat reproductive tissues. Western blot analysis showed that expression of L-arginine:glycine amidinotransferase was limited to the kidney. On the other hand, high levels of the mRNAs for both guanidinoacetate methyltransferase and Sadenosylhomocysteine hydrolase were expressed in the testis and epididymis as well as the liver and kidney. Cr transporter mRNA was highly expressed in the seminal vesicle and vas deferens. These results suggest that the source of Cr in the male reproductive tract varies depending on the tissue; in the testes and epididymides, Cr is synthesized from guanidinoacetate, while in the seminal vesicles, Cr is transported from blood. Previous and present findings suggest the importance of Cr metabolism and/or transport for reproductive functions.

Quantitative analysis of the high-affinity binding sites for [3H]ouabain in the rat vas deferens and their immunological identification as the alpha 2 isoform of Na+/K(+)-ATPase

Binding assays were performed with [3H]ouabain to investigate the presence of, and to characterize, a Na+/K(+)-ATPase isoform with high affinity for cardiac glycosides in the rat vas deferens. Nonlinear regression analysis of equilibrium experiments carried out with crude preparations in a Mg-Pi medium indicated the presence of high-affinity sites characterized with good precision (individual coefficients of variation = 11-35%) by their density (Bmax = 0.42 to 0.72 pmol/mg protein) and dissociation constant (Kd = 0.069 to 0.136 microM) values. The values of the dissociation rate constant (kappa-1) and the association rate constant (kappa+1) for these sites were 0.151 to 0.267 min-1 and 2.87 to 3.60 microM-1.min-1, respectively. A higher number of low-affinity sites (Kd around 15 microM), supposed to correspond to the alpha 1 isoform, was also identified, but their Kd and Bmax values were not quantified precisely in this crude preparation. Western blot assays indicated hybridization with specific anti-alpha 1 and anti-alpha 2 isoform antibodies but not with anti-alpha 3 isoform antibody. Taken together, the present results indicate the existence of a low proportion of the alpha 2 isoform of Na+/K(+)-ATPase in the rat vas deferens that can be quantified precisely by [3H]ouabain binding even in a crude membrane preparation that is suitable for studies under conditions of plasticity.

Nitric oxide synthase is co-localized with vasoactive intestinal polypeptide in postganglionic parasympathetic nerves innervating the rat vas deferens

Cross-sections of the vas deferens taken from control adult male rats showed positive histochemical reactivity to acetylcholinesterase and immunoreactivity for antibodies to protein gene product 9.5, tyrosine hydroxylase, neuropeptide Y, vasoactive intestinal polypeptide, nitric oxide synthase and calcitonin gene-related peptide. Immunoreactivity to substance P was very sparse. Histochemical reactivity to acetylcholinesterase and immunoreactivity to vasoactive intestinal polypeptide and nitric oxide synthase was concentrated in the subepithelial lamina propria and inner smooth muscle layers. Complete surgical denervation resulting from transection of the nerve arising from the pelvic ganglion which supplies the vas deferens totally abolished the immunoreactivity to all of the antibodies tested as well as the histochemical reactivity to acetylcholinesterase. In sections of the prostatic end of the vas deferens taken from rats neonatally pretreated with capsaicin, immunoreactivity to calcitonin gene-related peptide and substance P was reduced by 75 and 83%, respectively. Immunoreactivity to neuropeptide Y, vasoactive intestinal polypeptide and nitric oxide synthase was similar in tissue sections taken from capsaicin-treated rats and those taken from control tissues. Pretreatment of rats with guanethidine or 6-hydroxydopamine decreased immunoreactivity to tyrosine hydroxylase and neuropeptide Y by 60-70%, but immunoreactivity to substance P, vasoactive intestinal polypeptide and nitric oxide synthase was unchanged, while immunoreactivity to calcitonin gene-related peptide and acetylcholinesterase staining was increased by guanethidine but not by 6-hydroxydopamine treatment. Triple labelling experiments showed nitric oxide synthase, vasoactive intestinal polypeptide and acetylcholinesterase all to be co-localized in some nerve fibres. These results indicate that the nitric oxide synthase contained in the nerve fibres innervating the rat vas deferens is unaffected by pretreatment of rats with capsaicin, 6-hydroxydopamine or guanethidine but is abolished by surgical denervation, of postganglionic parasympathetic, sympathetic and sensory nerves. Therefore it appears that nitric oxide synthase is co-localized with vasoactive intestinal polypeptide in the postganglionic parasympathetic nerves which innervate the rat vas deferens.