Penile Corpus Cavernosum Tissue Research Articles

Interaction of Icariin from Epimedium koreanum and Udenafil on the Relaxation of Rabbit Penile Corpus Cavernosum Tissue

Interaction of Icariin from Epimedium koreanum and Udenafil on the Relaxation of Rabbit Penile Corpus Cavernosum Tissue

MP79-07 EFFECT OF NEAR-INFRARED LASER TREATMENT ON IMPROVING ERECTILE FUNCTION IN RATS WITH DIABETES MELLITUS

You have accessJournal of UrologyCME1 Apr 2023MP79-07 EFFECT OF NEAR-INFRARED LASER TREATMENT ON IMPROVING ERECTILE FUNCTION IN RATS WITH DIABETES MELLITUS Lin Yang, Guoxiong Liu, Dali Jiang, Guiting Lin, Hengtong Fan, Zejun Ren, Bing Yang, Liyue Mu, Tom F Lue, and Dalin He Lin YangLin Yang More articles by this author , Guoxiong LiuGuoxiong Liu More articles by this author , Dali JiangDali Jiang More articles by this author , Guiting LinGuiting Lin More articles by this author , Hengtong FanHengtong Fan More articles by this author , Zejun RenZejun Ren More articles by this author , Bing YangBing Yang More articles by this author , Liyue MuLiyue Mu More articles by this author , Tom F LueTom F Lue More articles by this author , and Dalin HeDalin He More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003356.07AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Diabetes mellitus induced erectile dysfunction (DMED) is difficult to treat. The oxidative stress (OS) created by DM is a major cause of injuries to the corpus cavernosum (CC), thereby resulting in ED. Near-infrared (NIR) laser has already been shown to be effective in treating multiple brain disorders due to its anti-OS effect. In this study we want to investigate whether an NIR laser improves the erectile function of DMED rats through its anti-OS effect. METHODS: Knowing its advantage of reasonable deep tissue penetration and good photo activation on mitochondria, a NIR laser with wavelength of 808nm was used in the experiment. Since the internal and external CC was covered by different tissue layers, the laser penetration rates of the internal and external CC were measured separately. Different radiant exposure settings were applied: in the initial experiment, 40 male SD rats were randomly assigned to five groups, normal controls (NC), and STZ-induced DM rats that 10 weeks later received various radiant exposures (J/cm2) from the NIR laser (DM0J, DM1J, DM2J, and DM4J) in the subsequent 2 weeks. Erectile function was then assessed 1 week after NIR treatment. It was found the initial radiant-exposure setting was not optimal according to the Arndt–Schulz rule. We followed with a second experiment using a different radiant exposure setting. Forty male rats were randomly divided into five groups (NC, DM0J, DM4J, DM8J, and DM16J), and the NIR laser was again applied according the new setting and erectile function was assessed as in the first experiment. Histologic, biochemical analyses and proteomic were then conducted. RESULTS: Recovery of erectile function of varying degrees was observed in the NIR treatment groups, and radiant exposure of 4 J/cm2 achieved optimal results. The NIR4J group showed improvement in mitochondrial function and in morphology in DM rats, and it was found that OS levels were significantly reduced by NIR exposure. The tissue structure of the CC was also improved by NIR exposure. The proteomics analysis confirming multiple biologic processes had been changed by DM and NIR. CONCLUSIONS: NIR laser activated mitochondria, improved OS, repaired the damage to penile CC tissue structures caused by DM, and improved erectile function in DM rats. These results thus raise the possibility that human patients with DMED may respond to NIR therapy in a manner that parallels the responses we observed in animal study. Source of Funding: Key R&D Plan of Shaanxi Province (2022SF-531) © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e1143 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Lin Yang More articles by this author Guoxiong Liu More articles by this author Dali Jiang More articles by this author Guiting Lin More articles by this author Hengtong Fan More articles by this author Zejun Ren More articles by this author Bing Yang More articles by this author Liyue Mu More articles by this author Tom F Lue More articles by this author Dalin He More articles by this author Expand All Advertisement PDF downloadLoading ...

Effect of near-infrared laser treatment on improving erectile function in rats with diabetes mellitus.

Diabetes mellitus-induced erectile dysfunction is difficult to treat. The oxidative stress created by diabetes mellitus is a major cause of injuries to the corpus cavernosum, thereby resulting in erectile dysfunction. Near-infrared laser has already been shown to be effective in treating multiple brain disorders because of its antioxidative stress effect. To investigate whether a near-infrared laser improves the erectile function of diabetes mellitus-induced erectile dysfunction rats through its antioxidative stress effect. Knowing its advantage of reasonable deep tissue penetration and good photoactivation on mitochondria, a near-infrared laser with wavelength of 808nm was used in the experiment. Since the internal and external corpus cavernosum were covered by different tissue layers, the laser penetration rates of the internal and external corpus cavernosum were measured separately. Different radiant exposure settings were applied: in the initial experiment, 40 male Sprague-Dawley rats were randomly assigned to five groups, normal controls, and streptozotocin-induced diabetes mellitus rats that 10weeks later received various radiant exposures (J/cm2 ) from the near-infrared laser (DM0J(DM+NIR 0 J/cm2 ), DM1J, DM2J, and DM4J) in the subsequent 2weeks. Erectile function was then assessed 1week after near-infrared treatment. It was found that the initial radiant exposure setting was not optimal according to the Arndt-Schulz rule. We performed a second experiment using a different radiant exposure setting. Forty male rats were randomly divided into five groups (normal controls, DM0J, DM4J, DM8J, and DM16J), and the near-infrared laser was again applied according to the new setting, and erectile function was assessed as in the first experiment. Histologic, biochemical, and proteomic analyses were then conducted. Recovery of erectile function of varying degrees was observed in the near-infrared treatment groups, and radiant exposure of 4 J/cm2 achieved optimal results. The DM4J group showed improvement in mitochondrial function and morphology in diabetes mellitus rats, and it was found that oxidative stress levels were significantly reduced by near-infrared exposure. The tissue structure of the corpus cavernosum was also improved by near-infrared exposure. The proteomics analysis confirming multiple biologic processes were changed by diabetes mellitus and near-infrared. Near-infrared laser activated mitochondria, improved oxidative stress, repaired the damage to penile corpus cavernosum tissue structures caused by diabetes mellitus, and improved erectile function in diabetes mellitus rats. These results thus raise the possibility that human patients with diabetes mellitus-induced erectile dysfunction may respond to near-infrared therapy in a manner that parallels the responses we observed in animal study.

Effect of low androgen levels on transient receptor potential channels expression in rat penile corpus cavernosum tissue and its relationship with erectile function.

The exact mechanism by which testosterone deficiency causes ED has not yet been elucidated. TRPC is involved in the process of smooth muscle cell contraction and relaxation. The effect of androgens on TRPCs and their relationship with erectile function are currently unclear. Thirty male SD rats were randomly divided into six groups: control group, castration group, castration + testosterone (T) group (cast + T), control + transfection group (control + trans), control + empty transfection group and castration + transfection group (cast + trans). The transfection group rats were given with lentivirus (1 × 108 TU/mL, 15 μl) carrying the siRNA targeting TRPC4 gene in the rat penile cavernous tissue at 4 weeks after castration. The tests were performed at 5 weeks after castration. Comparing the cast group with the control, the ICPmax/MAP, p-eNOS/eNOS and NO levels in the rat penile tissue were significantly lower (p < 0.01) and the level of TRPC3, TRPC4 and TRPC6 in the rat penile tissue was significantly increased (p < 0.01). When the cast + trans group was compared to the cast group, ICPmax/MAP was markedly higher (p < 0.05), and the level of the TRPC4 was remarkably lower (p < 0.05). Low androgen levels might inhibit an erectile function through up-regulation of the expression of TRPC3, TRPC4 and TRPC6 in rat penile cavernous tissue. Inhibition the level of TRPC4 in rat penile tissue may improve the erectile function in low androgen levels.

Aldosterone induces inflammatory cytokines in penile corpus cavernosum by activating the NF-κB pathway

Emerging evidence indicates that aldosterone and mineralocorticoid receptors (MRs) are associated with the pathogenesis of erectile dysfunction. However, the molecular mechanisms remain largely unknown. In this study, freshly isolated penile corpus cavernosum tissue from rats was treated with aldosterone, with or without MRs inhibitors. Nuclear factor (NF)-kappa B (NF-κB) activity was evaluated by real-time quantitative PCR, luciferase assay, and immunoblot. The results demonstrated that mRNA levels of the NF-κB target genes, including inhibitor of NF-κB alpha (IκB-α), NF-κB1, tumor necrosis factor-alpha (TNF-α), and interleukin 6 (IL-6), were higher after aldosterone treatment. Accordingly, phosphorylation of p65/RelA, IκB-α, and inhibitor of NF-κB kinase-β was markedly increased by aldosterone. Furthermore, knockdown of MRs prevented activation of the NF-κB canonical pathway by aldosterone. Consistent with this finding, ectopic overexpression of MRs enhanced the transcriptional activation of NF-κB by aldosterone. More importantly, the MRs antagonist, spironolactone blocked aldosterone-mediated activation of the canonical NF-κB pathway. In conclusion, aldosterone has an inflammatory effect in the corpus cavernosum penis, inducing NF-κB activation via an MRs-dependent pathway, which may be prevented by selective MRs antagonists. These data reveal the possible role of aldosterone in erectile dysfunction as well as its potential as a novel pharmacologic target for treatment.

ShRNA Constructs Targeting IGFBP-3 Alleviate Age Related Erectile Dysfunction in the Rat

We investigated whether injecting shRNA constructs targeting IGFBP-3 in the penis of old rats would improve erectile function. The most validated IGFBP-3 shRNA plasmid vector (pGPU6/GFP/Neo-shIGFBP-3) was prepared and injected in penile corpus cavernosum tissue. A total of 30 old (age 24 months) male Sprague Dawley® rats were randomly divided into 3 groups, including 10 each that received phosphate buffered saline only (100 μl), pGPU6/GFP/Neo-shNC (100 μg) and the most validated plasmid constructs pGPU6/GFP/Neo-shIGFBP-3 (100 μg). At 4 weeks the erectile response was measured as intracavernous pressure. The percent ofsmooth muscle in corpus cavernosum tissue was evaluated. Nitric oxide synthase activity and the cGMP concentration in penile tissue were also analyzed. IGFBP-3 was estimated in penile tissue by Western blot, real-time reverse transcriptase-polymerase chain reaction and immunohistochemistry. pGPU6/GFP/Neo-shIGFBP-3 corrected the impaired erectile response in aged rats compared with the response in those injected with phosphate buffered saline and pGPU6/GFP/Neo-shNC (each p <0.01). The percent of cavernous smooth muscle was increased in the pGPU6/GFP/Neo-shIGFBP-3 group. Nitric oxide synthase activity and the cGMP concentration were also significantly increased in rats treated with pGPU6/GFP/Neo-shIGFBP-3. IGFBP-3 shRNA effectively reduced IGFBP-3 mRNA and protein expression in penile corpus cavernosum tissue. Decreasing IGFBP-3 expression by plasmid expressed shRNA improved erectile function in aged rats. The therapy may modulate smooth muscle integrity and increase the cGMP concentration. This may be a new direction for treating erectile dysfunction in clinical practice.

Involvement of Large‐Conductance Ca2+‐Activated K+ Channels in both Nitric Oxide and Endothelium‐Derived Hyperpolarization‐Type Relaxation in Human Penile Small Arteries

Large-conductance Ca(2+) -activated K(+) channels (BKC a ), located on the vascular smooth muscle, play an important role in regulation of vascular tone. In penile corpus cavernosum tissue, opening of BKC a channels leads to relaxation of corporal smooth muscle, which is essential during erection; however, there is little information on the role of BKC a channels located in penile vascular smooth muscle. This study was designed to investigate the involvement of BKC a channels in endothelium-dependent and endothelium-independent relaxation of human intracavernous penile arteries. In human intracavernous arteries obtained in connection with transsexual operations, change in isometric force was recorded in microvascular myographs, and endothelium-dependent [nitric oxide (NO) and endothelium-derived hyperpolarization (EDH)-type] and endothelium-independent (NO-donor) relaxations were measured in contracted arteries. In penile small arteries contracted with phenylephrine, acetylcholine evoked NO- and EDH-type relaxations, which were sensitive to iberiotoxin (IbTX), a selective blocker of BKC a channels. Iberiotoxin also inhibited relaxations induced by a NO-donor, sodium nitroprusside. NS11021, a selective opener of BKC a channels, evoked pronounced relaxations that were inhibited in the presence of IbTX. NS13558, a BKC a -inactive analogue of NS11021, failed to relax human penile small arteries. Our results show that BKC a channels are involved in both NO- and EDH-type relaxation of intracavernous penile arteries obtained from healthy men. The effect of a selective opener of BKC a channels also suggests that direct activation of the channel may be an advantageous approach for treatment of impaired endothelium-dependent relaxation often associated with erectile dysfunction.

750 CORRECTION OF DIABETIC ERECTILE DYSFUNCTION WITH ADIPOSE DERIVED STEM CELLS MODIFIED WITH THE VASCULAR ENDOTHELIAL GROWTH FACTOR GENE

You have accessJournal of UrologySexual Function/Dysfunction/Andrology: Basic Research1 Apr 2011750 CORRECTION OF DIABETIC ERECTILE DYSFUNCTION WITH ADIPOSE DERIVED STEM CELLS MODIFIED WITH THE VASCULAR ENDOTHELIAL GROWTH FACTOR GENE XiangZhou Sun, GuiHua Liu, ChunHua Deng, and Yuanyuan Zhang XiangZhou SunXiangZhou Sun Guangzhou, China, People's Republic of More articles by this author , GuiHua LiuGuiHua Liu Winston-Salem, NC More articles by this author , ChunHua DengChunHua Deng Guangzhou, China, People's Republic of More articles by this author , and Yuanyuan ZhangYuanyuan Zhang Winston-Salem, NC More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.1775AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Erectile dysfunction (ED) is three times more common in diabetic men than in nondiabetic men. The main pathogenesis in diabetes mellitus related ED (DMED) is endothelial dysfunction. Our previous study demonstrated that vascular endothelial growth factor (VEGF) levels were abnormal in the penile corpus cavernosum tissue of DMED rats. The aim of this study was to determine whether adipose derived stem cells (ASC) expressing VEGF can be used as a therapeutic approach to repair injured endothelial cells in the penile corpus cavernosum of DMED rats. METHODS ASC were isolated from adipose tissue in the groin area in normal Sprague-Dawley rats, and the cells were cultured and expanded in vitro. Stable expression of VEGF in ASC was established. Diabetes was induced in rats via intraperitoneal injection of streptozotocin (40mg/kg), and we utilized apomorphine (100μg/kg) to screen the DMED models for erectile dysfunction. Five groups were used (n=12 rats/ group): Group 1 (G1) animals received a intracavernous injection of lentivirus-VEGF; G2 animals received ASC injected into the corpora cavernosum; G3 animals received an injection of VEGF-expressing ASC; G4 animals received an injection of normal saline as a negative control. These 4 groups consisted of DMED rats, and a fifth group (G5) consisted of normal rats as controls. Erectile function, including intracavernosal pressure and mean systemic arterial pressure, was measured at days 7 and 28 after injection. The penile tissues were harvested and the components of the VEGF system, including VEGF, fetal liver kinase 1(Flk-1), and endothelial nitric oxide synthase (eNOS), were assessed in the penile tissue with immunohistochemistry and Western blot. RESULTS Up to 95% of the virally-transfected ASC expressed VEGF. On day 7 after injection, the number of ASC increased within the corporal tissue and by day 28, erectile function improved in DMED rats. Improved erectile function was associated with increased expression of VEGF, Flk-1 and eNOS protein. Although ASC implantation or lentivirus-VEGF injection alone each increased erectile function of DMED rats, the degree of improvement was significantly lower than in the group that received VEGF-expressing ASC (p<0.01). CONCLUSIONS ASC expressing VEGF produced a therapeutic effect and appeared to restore erectile function in diabetic rats by enhancing VEGF-stimulated cell function via VEGF, Flk-1, and eNOS. This study highlights the potential for clinical use of adult stem cell-based therapy for the treatment of ED. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e301-e302 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information XiangZhou Sun Guangzhou, China, People's Republic of More articles by this author GuiHua Liu Winston-Salem, NC More articles by this author ChunHua Deng Guangzhou, China, People's Republic of More articles by this author Yuanyuan Zhang Winston-Salem, NC More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Effect of aldosterone on isolated human penile corpus cavernosum tissue

To clarify the physiological effects of aldosterone on human penile corpus cavernosum (hPCC) tissue, as aldosterone has a wider physiological action than just the maintenance of electrolyte balance, and there are mineralocorticoid receptors, i.e. aldosterone receptors, in hPCC tissue. Specimens of hPCC were obtained from 10 patients (mean age 38 years, range 21-75), with informed consent and approval by the local ethics committee. One patient had a penectomy because of penile cancer, and nine had a penile biopsy because of erectile dysfunction. Patients with diabetes mellitus, hypertension or ischaemic heart disease were excluded. In a pharmacological study we evaluated the effect of aldosterone on the isolated hPCC tissues. Aldosterone caused no significant change in resting tension and did not affect the nitric oxide-dependent relaxation reaction. However, the dose-response curve of noradrenaline was shifted to the left when the strip preparation was treated with aldosterone (1 x 10(-5)M) for 20 min before administering noradrenaline. Moreover, the shift to the left was completely blocked when spironolactone (anti-aldosterone agent) was added as a pre-treatment. Pre-treatment with aldosterone also significantly extended the mean (SEM) time required to reach 50% relaxation of a noradrenaline-induced contraction, of 9.3 (1.5) min, vs the control, of 5.2 (1.0) min (P = 0.002). Aldosterone has no direct contractile action or a relaxant action on human penile cavernous tissue, but acts to significantly enhance the noradrenaline-induced contraction. The effect on the noradrenaline-induced contraction is probably caused by aldosterone enhancing the affinity of the alpha-receptors for noradrenaline in hPCC. We suggest that aldosterone acts to enhance contraction of hPCC tissue, and is one of the restraining factors for human penile erection.

Nebivolol induces eNOS activation and NO-liberation in murine corpus cavernosum

Erectile function is critically dependent upon the activation of the endothelial nitric oxide synthase (eNOS) in the smooth muscle cells of penile corpus cavernosum tissue. Nebivolol is a β 1-selective β-adrenoceptor blocker (β-ARB) with additional vasodilating properties, which have been attributed to eNOS-activation. Our study investigated whether nebivolol is able to increase eNOS activity in erectile tissue. Murine penile tissue was incubated in an organ bath under control conditions and in the presence of nebivolol or metoprolol. Immunofluorescence staining was performed using specific antibodies against eNOS-activation or eNOS-serine 1177 phosphorylation. Corpus cavernosum smooth muscle tissue was identified using a smooth muscle actin antibody. In addition, slices of murine erectile tissue were incubated with diaminofluorescein (DAF), a specific fluorescence marker for NO-liberation. Under control conditions and after application of metoprolol, we observed a small eNOS-activation and serine 1177-phosphorylation in murine corpus cavernosum tissue. A significant increase in eNOS-activation and serine 1177-phosphorylation of eNOS was observed only in the presence of nebivolol (10 μM). These alterations of the eNOS protein induced after application of nebivolol were associated with a time-dependent increase in DAF fluorescence in murine erectile tissue. We conclude that β-adrenoceptor blockers differentially influence erectile tissue. Since cardiovascular diseases are often associated with the development of erectile dysfunction, the nebivolol-induced eNOS-activation in corpus cavernosum may be beneficial when treating patients suffering from cardiovascular disease.

Probing erectile function: S-(2-boronoethyl)-L-cysteine binds to arginase as a transition state analogue and enhances smooth muscle relaxation in human penile corpus cavernosum.

The boronic acid-based arginine analogue S-(2-boronoethyl)-L-cysteine (BEC) has been synthesized and assayed as a slow-binding competitive inhibitor of the binuclear manganese metalloenzyme arginase. Kinetic measurements indicate a K(I) value of 0.4-0.6 microM, which is in reasonable agreement with the dissociation constant of 2.22 microM measured by isothermal titration calorimetry. The X-ray crystal structure of the arginase-BEC complex has been determined at 2.3 A resolution from crystals perfectly twinned by hemihedry. The structure of the complex reveals that the boronic acid moiety undergoes nucleophilic attack by metal-bridging hydroxide ion to yield a tetrahedral boronate anion that bridges the binuclear manganese cluster, thereby mimicking the tetrahedral intermediate (and its flanking transition states) in the arginine hydrolysis reaction. Accordingly, the binding mode of BEC is consistent with the structure-based mechanism proposed for arginase as outlined in Cox et al. [Cox, J. D., Cama, E., Colleluori D. M., Pethe, S., Boucher, J. S., Mansuy, D., Ash, D. E., and Christianson, D. W. (2001) Biochemistry 40, 2689-2701.]. Since BEC does not inhibit nitric oxide synthase, BEC serves as a valuable reagent to probe the physiological relationship between arginase and nitric oxide (NO) synthase in regulating the NO-dependent smooth muscle relaxation in human penile corpus cavernosum tissue that is required for erection. Consequently, we demonstrate that arginase is present in human penile corpus cavernosum tissue, and that the arginase inhibitor BEC causes significant enhancement of NO-dependent smooth muscle relaxation in this tissue. Therefore, human penile arginase is a potential target for the treatment of sexual dysfunction in the male.

Phentolamine mesylate relaxes penile corpus cavernosum tissue by adrenergic and non-adrenergic mechanisms.

We investigated the biochemical and physiological mechanisms of action of phentolamine mesylate (Vasomax) in regulating erectile tissue smooth muscle contractility in human and rabbit corpus cavernosum. The binding activity of phentolamine was investigated in a cell-free system by displacement of specific and selective radiolabelled ligands to alpha 1 and 2 adrenergic receptors. The physiologic activity of phentolamine-mediated relaxation of adrenergic and non-adrenergic pre-contracted erectile tissue strips of human and rabbit corpus cavernosum were studied in organ bath chambers. In corpus cavernosum membranes, phentolamine displaced binding of the selective alpha 1 receptor antagonists [125I]HEAT and [3H]prazosin and the alpha 2 receptor antagonists [3H]rauwolscine and [3H]RX 821002 with relatively high affinity. Phentolamine caused concentration dependent relaxation in erectile tissue strips pre-contracted with adrenergic agonists phenylephrine, norepinephrine, oxymetazoline and UK 14,304, as well as with non-adrenergic contractile agents endothelin and KCl. Biochemical and physiologic studies reveal that the concentration of phentolamine required to displace half maximal binding or to produce half-maximal relaxation was similar to that found in human plasma 30 min after ingestion of 40 mg of Vasomax. Reversible inhibition of nitric oxide synthase by L-nitroarginine or mechanical disruption of endothelium diminished non-adrenergic phentolamine-mediated erectile tissue relaxation. Phentolamine mesylate induced relaxation of corpus cavernosum erectile tissue by direct antagonism of alpha 1 and 2 adrenergic receptors and by indirect functional antagonism via a non-adrenergic, endothelium-mediated mechanism suggesting nitric oxide synthase activation.

Prostanoid Production in Rabbit Corpus Cavernosum. II. Inhibition of Oxidative Stress

Purpose To investigate the effects of reoxygenation following hypoxia on prostanoid production in rabbit penile corpus cavernosum tissue (RCC) in organ culture. Materials and Methods Strips of RCC were incubated in organ culture media under either 21 percent O 2 (control, PO 2 approximately 167 mm.Hg) or 0 percent O 2 (hypoxia, PO 2 approximately 27 mm.Hg) followed by a reoxygenationi period with 21 percent O 2, in the presence or absence of exogenous arachidonate, Tiron or catalase. Prostanoids were measured in collected media by radioimmunoassay. Malondialdehyde levels were measured in RCC following exposure to either control or hypoxia-reoxygenation conditions. Results Under hypoxic conditions, basal release of prostanoids (PGI 2, PGF 2 alpha, PGE 2 and TXB 2) was inhibited. Although this inhibition was reversible upon reoxygenation, the recovery was delayed, requiring at least 2 hours of exposure to 21 percent oxygen to reestablish prostanoid production. Reoxygenation also caused lipid peroxidation as measured by an increase in malondialdehyde levels. When reoxygenation was done in the presence of exogenous arachidonate, recovery of PGI 2 production was complete by 1 hour. Reoxygenation in the presence of a scavenger of reactive oxygen species (Tiron) or catalase significantly improved the recovery rate of PGI 2 production. Conclusions These results show that reoxygenation of hypoxic tissue generates oxidative stress that interferes with the recovery of prostanoid production by alteration of a biosynthetic point(s) upstream from prostaglandin H synthase (PGHS) including, at least, phospholipid peroxidation.

Prostanoid Production in Rabbit Corpus Cavernosum: I. Regulation by Oxygen Tension

Purpose To investigate the effects of oxygen tension on prostanoid synthesis in rabbit penile corpus cavernosum tissue (RCC) in organ culture. Materials and Methods Strips of rabbit corpus cavernosum were incubated in organ culture media under varying oxygen conditions (0 percent, 12 percent and 21 percent oxygen), in the presence or absence of acetylcholine and arachidonate stimulation. Prostanoids were measured in collected media by radioimmunoassay. Prostaglandin H synthase (PGHS) protein levels and mRNA PGHS expression were measured under both 0 percent and 21 percent oxygen conditions. Results Basal and acetylcholine-stimulated PGI 2 release was progressively diminished as a function of diminishing oxygen tension (pO 2 from approximately 165 to 25 mm.Hg). The basal and stimulated production of other prostanoids, thromboxane A 2, PGF 2 alpha and PGE 2, was also significantly inhibited under 0 percent oxygen (approximately 25 mm.Hg) conditions. However, incubation under 0 percent oxygen did not alter PGHS protein levels nor mRNA PGHS expression. Cavernosal strips incubated under 0 percent oxygen but supplemented with exogenous arachidonate (10 micromolar) maintained significantly lower PGI 2 production than tissues exposed to 21 percent oxygen (approximately 165 mm.Hg). Conclusions These data demonstrate that oxygen tension regulates prostaglandin production in corporal tissue. The reduction in prostanoid production during hypoxia can be attributed to inhibition of PGHS activity rather than the expression of the enzyme. In view of the role of PGI 2 as an inhibitor of platelet aggregation and white cell-endothelial adhesion, our findings may provide mechanistic insight into the alteration in corporal blood homeostasis during ischemic-hypoxic priapism.

Vasoactive intestinal polypeptide (VIP) and peptide histidine methionine (PHM) in human penile corpus cavernosum tissue and circumflex veins: localization and in vitro effects.

Localization and functional effects of vasoactive intestinal polypeptide (VIP) and peptide histidine methionine (PHM), two peptides derived from a common precursor molecule, were investigated in isolated preparations from human penile corpus cavernosum (CC) and circumflex vein (CV). VIP- and PHM-immunoreactivity (IR) was demonstrated in both CC and CV. The concentrations of VIP-IR and PHM-IR in CC tissue were 54.4 +/- 15.3, and 42.0 +/- 7.5 pmol g-1 wet weight respectively with a VIP/PHM ratio of 1.5 +/- 0.4 (mean +/- SEM). The corresponding values for CV tissues were 28.0 +/- 7.7 and 9.6 +/- 2.6 pmol g-1 wet weight with a VIP/PHM ratio of 3.1 +/- 0.4. CC and CV displayed VIP- and PHM-IR confined to nerve fibres in close relation to bundles of smooth muscle cells and blood vessels in both tissues. In vitro, VIP and PHM had no effects in unstimulated tissue preparations. Both peptides concentration-dependently (10(-9)-10(-6) M) relaxed CC and CV preparations precontracted with 3 x 10(-6) M noradrenaline. In CC the maximum relaxant effect of VIP and PHM was 22 +/- 11% and 9 +/- 9% and in CV the corresponding values were 82 +/- 8% and 93 +/- 3% respectively. The present study supports the hypothesis of VIP and PHM as neurotransmitters and/or neuromodulators in the nervous control of penile erection.

Neuropeptide Y (NPY) in Human Penile Corpus Cavernosum Tissue and Circumflex Veins—Occurrence and in Vitro Effects

The concentration and distribution of neuropeptide Y (NPY) within the penile corpus cavernosum (CC) and in penile circumflex veins (CV) from healthy potent males was investigated by immunochemistry and immunohistochemistry. The concentrations were assessed to 28.6pmol/gm. (CC) and 15.8pmol/gm. (CV) respectively. Gel filtration on CC tissue extracts demonstrated a single peak of NPY-immunoreactivity (NPY-IR) similar to synthetic human NPY. The NPY-IR was confined to nerve fibers seemingly innervating smooth muscle cells. In vitro myographic examinations demonstrated contractile activation by NPY in 2/8 CC strips and in 5/8 CV strips. The mean contractile force was 1.17 ± 0.62mN (18.3 ± 15.8% of the K+-induced contraction) and 2.42 ± 0.42mN(31 ± 12%) respectively. NPY 10−7and 10−6 M displayed a potentiating effect on the response to NA 10−9 in one of six CC and four of six CV preparations. It is suggested that NPY could add to the contractile effect of NA in detumescence and in maintenance of the resting state; contribution of NPY to the veno-occlusive mechanism at initiation of erection is another putative physiological function.

Effect of moxisylyte hydrochloride on isolated human penile corpus cavernosum tissue

The effect of moxisylyte hydrochloride on isolated human penile corpus cavernosum tissue was investigated and compared with other a− adrenergic antagonists. Moxisylyte produced a concentration-dependent relaxation of a norepinephrine-induced (1×10 −5M contraction of the corpus cavernosum tissue. Pretreatment with 1×10 −6M doses of moxisylyte reduced competitively the norepinephrine-induced contraction. The competitive effect of prazosin was strongest among four tested agents, followed by phentolamine, moxisylyte, and then yohimbine. The activity ratio for each antagonist is 2.4 for moxisylyte, as compared with 28.2 for prazosin, 6.7 for phentolamine, and 1.6 for yohimbine respectively. Moxisylyte hydrochloride is an agent with potential clinical and research uses capable of producing erection when injected intra-cavernously.

Cholinergic neurotransmission in human corpus cavernosum. I. Responses of isolated tissue

To investigate the role of cholinergic neurotransmission in erection, human penile corpus cavernosum tissue was studied. Electrical stimulation of strips of corpus cavernosum suspended in an organ chamber induced contractions and relaxations that were blocked by tetrodotoxin. The contractions also were blocked by bretylium and prazosin. Norepinephrine and phenylephrine contracted the isolated strips and this response was prevented by prazosin. Electrical stimulation-induced relaxations were enhanced by bretylium and physostigmine and partially blocked by atropine. The effect of atropine, but not that of physostigmine, was prevented by bretylium. Corporal strips contracted with norepinephrine relaxed to acetylcholine; this effect was blocked by atropine and enhanced by physostigmine. Strips lacking endothelium contracted normally with norepinephrine, but the relaxation caused by acetylcholine was virtually abolished. Thus endothelium lining the lacunar spaces within human corpus cavernosum is required for the relaxation caused by exogenous acetylcholine. There may be three neurotransmitter effector systems that control corpus cavernosum smooth muscle tone: adrenergic (excitatory), cholinergic (inhibitory), and nonadrenergic noncholinergic (inhibitory). Cholinergic nerves do not dilate or constrict directly the smooth muscle but may modulate other neuroeffector systems and/or the endothelium.