Chronic inhibition of nitric-oxide synthase induces hypertension and erectile dysfunction in the rat that is not reversed by sildenafil

Endothelial and Vascular Smooth Muscle Dysfunction in Hypertension

The development of essential hypertension involves several factors. Vascular dysfunction, characterized by endothelial dysfunction, low-grade inflammation and structural remodeling, plays an important role in the initiation and maintenance of essential hypertension. Although the mechanistic pathways by which essential hypertension develops are poorly understood, several pharmacological classes available on the clinical settings improve blood pressure by interfering in the cardiac output and/or vascular function. This review is divided in two major sections. The first section depicts the major molecular pathways as renin angiotensin aldosterone system (RAAS), endothelin, nitric oxide signalling pathway and oxidative stress in the development of vascular dysfunction. The second section describes the role of some pharmacological classes such as i) RAAS inhibitors, ii) dual angiotensin receptor-neprilysin inhibitors, iii) endothelin-1 receptor antagonists, iv) soluble guanylate cyclase modulators, v) phosphodiesterase type 5 inhibitors and vi) sodium-glucose cotransporter 2 inhibitors in the context of hypertension. Some classes are already approved in the treatment of hypertension, but others are not yet approved. However, due to their potential benefits these classes were included.

Effect of phosphodiesterase-4 inhibitor rolipram on colonic hypermotility in water avoidance stress rat model

BACKGROUND

Phosphodiesterase (PDE) inhibition has been reported to play a role in regulating gut motility, but the evidence is insufficient, and the mechanism remains unknown. The aim of this study was to investigate the possible role of phosphodiesterase-4 (PDE4) inhibitor rolipram in water avoidance stress-induced colonic hypermotility.

METHODS

A rat model of irritable bowel syndrome (IBS) with diarrhea (IBS-D) was established by water avoidance stress (WAS). Intestinal motility was assessed by fecal pellets expulsion per hour. The cyclic adenosine monophosphate (cAMP) and nitric oxide (NO) level in colon tissue were detected using ELISA assay and the Griess test, respectively. Western blotting was performed to assess the protein level of PDE, PKA/p-CREB, and neuronal nitric oxide synthase (nNOS) in the colon. To determine the role of rolipram in gut motility, the rats of the WAS + Rolipram and Rolipram group were injected with rolipram intraperitoneally. The colonic contractile activity was recorded with a RM6240 multichannel physiological signal system.

KEY RESULTS

WAS-induced gastrointestinal hypermotility and increased defecation in rats. After repeated stress, protein levels of PDE4 in the colon were promoted while PKA/p-CREB and nNOS were highly decreased. cAMP content in colon tissue did not change significantly. However, NO content decreased after WAS, and rolipram partly enhanced NO in WAS-exposed rats. In addition, intraperitoneal injection of rolipram partly inhibited the colonic motility in vivo. Meanwhile, we observed rolipram inhibited the contraction of colonic smooth muscle strips, and this inhibitory effect was abolished by Nω-Nitro-L-arginine (L-NNA), a nitric oxide synthase (NOS) inhibitor, tetrodotoxin (TTX), a blocker of neuronal voltage-dependent Na⁺ channels, Rp-Adenosine 3',5'-cyclic monophosphorothioate triethylammonium salt hydrate (Rp-cAMPS), an antagonist of cAMP.

CONCLUSIONS AND INFERENCES

Rolipram could relieve stress-induced gastrointestinal hypermotility. This effect may be partly through the cAMP-PKA-p-CREB pathway and NO pathway.

The Effects of Irisin on Nω-Nitro-L-arginine Methyl Ester Hydrochloride-Induced Hypertension in Rats

Background:

The cause of about 95% of hypertension, an important public health problem, is unknown. Intensive studies are underway to understand the physiopathology of hypertension. Irisin, a newly discovered hormone, has been reported to dilate vascular smooth muscle and lower blood pressure acutely.

Aims:

To investigate the effects of chronic irisin treatment on blood pressure and renal functions in a hypertension model established by nitric oxide synthase inhibition by treatment with Nω-nitro-L-arginine methyl ester hydrochloride.

Study Design:

Animal experimentation.

Methods:

Male Sprague−Dawley rats were divided into four groups (n=8). Control and irisin groups received an intravenous saline injection, hypertension and hypertension + irisin (hypertension + irisin) groups received 1.5 mg/100 g Nω-nitro-L-arginine methyl ester hydrochloride. Nω-nitro-L-arginine methyl ester hydrochloride (150 mg/L) was added to the drinking water of rats in groups hypertension and hypertension + irisin for three weeks. In the second week of the experiment, irisin (50 nmol/day) was given to rats in groups irisin and hypertension + irisin, and saline was administered to rats in groups control and hypertension for two weeks through subcutaneously placed osmotic minipumps. Blood pressure was measured by the tail-cuff plethysmography method. On the twenty-first day of the experiment, 24-hour urine, blood, and both kidneys of the rats were collected.

Results:

The hypertension group had elevated systolic, diastolic, and mean arterial blood pressure values compared with the control group, with decreased glutathione levels in tissue and serum, but an increase in serum oxidized glutathione level (p<0.05). Histopathologically, increased tubular injury, cast formation, glomerular sclerosis, and peritubular fibrosis levels were observed (p<0.05). Irisin treatment did not cause any significant change in blood pressure, renal functions, and injury scores. However, renal nitric oxide levels significantly increased, and endothelial nitric oxide synthase immunoreactivity was determined to be reduced (p<0.05).

Conclusion:

Treatment with chronic irisin at a physiological dose does not reduce blood pressure in an experimental model of hypertension. In different models of experimental hypertension, the effects of irisin administration at different doses and at different periods should be thoroughly investigated.

Gross saponin of Tribulus terrestris improves erectile dysfunction in type 2 diabetic rats by repairing the endothelial function of the penile corpus cavernosum

OBJECTIVE

To investigate the effect of gross saponins of Tribulus terrestris (GSTT) on erectile function in rats resulting from type 2 diabetes mellitus (T2DMED).

METHODS

The T2DMED model was constructed by high-fat and high-sugar feeding and streptozotocin injection. After 4 weeks of GSTT intervention. Intracavernous pressure (ICP) and mean arterial pressure (MAP) were measured in each group. The level of nitric oxide (NO) in the cavernous tissue was detected using the nitrate reductase method. The production of reactive oxygen species (ROS) was detected using DHE fluorescent probe detection. Cyclic adenosine monophosphate (cGMP) level was detected by enzyme-linked immunosorbent assay, and endothelial nitric oxide synthase (eNOS) was detected using immunohistochemistry. Masson staining was used to detect the cavernosal smooth muscle/collagen ratio. Apoptosis in endothelial cells was measured using TUNEL. Western blotting method to detect the protein expression level of eNOS, TIMP-1, cleaved caspase 3, and cleaved caspase 9.

RESULTS

After treatment, the ICP and ICP/MAP values of the GSTT were significantly higher than those of the T2DMED group (P<0.05). Unlike the T2DMED group, the GSTT group showed significantly increased NO levels (P<0.05) and decreased ROS levels (P<0.05). There was no significant difference between the GSTT group and the sildenafil group in increasing cGMP levels (P>0.05), and the mixed group had higher levels than these two groups (P<0.05). Immunohistochemistry and Western blotting showed that the expression of eNOS in the GSTT was significantly higher than that in the T2DMED groups (P<0.05). Masson staining showed that the smooth muscle/collagen ratio of the GSTT group was significantly higher than that of the T2DMED groups (P<0.05), the expression of TIMP-1 was lower than that of T2DMED group (P<0.05). TUNEL assay showed that the apoptotic index and cleaved caspase 3 and cleaved caspase 9 expression level of GSTT group were lower than that of the T2DMED group (P<0.05).

CONCLUSION

GSTT can protect T2DMED rats' erectile function by improving penile endothelial function and inhibiting cavernosum fibrosis, inhibiting apoptosis, and is synergistic with sildenafil.

Isolation and identification of nucleosides/nucleotides raising testosterone and NO levels of mice serum from Chinese chive (Allium tuberosum) leaves

Our previous study found that Chinese chive could significantly (p < 0.01) raise testosterone and nitric oxide (NO) levels in mice serum. However, the specific functional components of this traditional remedy are still unknown. In order to isolate and identify the active constituents from Chinese chive for enhancing testosterone and NO levels, the Chinese chive leaves were extracted by petroleum ether, ethyl acetate, n-butanol and water respectively. Results indicated that the n-butanol extract had a significant effect on NO and testosterone blood levels. Subsequently, n-butanol extract was further isolated by D101 macroporous adsorption and eluted with 50% ethanol and then isolated by Sephadex LH-20 and preparative high-performance liquid chromatography to obtain nucleosides. The fraction eluted with 70% ethanol was further isolated by RP-18 and pre-HPLC to obtain nucleotides. Four novel compounds were identified, and their effects on testosterone and NO levels of male mice were evaluated. Results showed that nucleotides, especially the adenosine in Chinese chive leaves, increased serum testosterone and NO levels in male mice, which had not been reported before. This finding might bring into perspective the treatment strategy for those doctors who treat hormone deficiencies, and might be suitable for using in functional food.

Energy restriction, exercise and atorvastatin treatment improve endothelial dysfunction and inhibit miRNA-155 in the erectile tissue of the aged rat

Background

Endothelial dysfunction underlies cardiovascular disease that frequently affects aged individuals. Characterized by local decrease in nitric oxide, it results from down-regulation of endothelial nitric oxide synthase (eNOS) expression/activity. Aiming to elucidate the molecular mechanisms involved in age-related endothelial dysfunction and to unveil potential therapeutic targets, we tested how diet pattern, exercise and atorvastatin modulate the expression of eNOS, inducible NOS (iNOS), endothelin-1, sirtuins (SIRT) and microRNA-155 in the erectile tissue of high-fat fed aged rats.

Methods

Sprague-Dawley male rats fed with high-fat diet until they completed 12 months were grouped and subjected to energy restriction (ER), ER and atorvastatin, or, ER, atorvastatin and physical exercise. Controls were fed with standard rodent chow. The blood pressure was measured using the tail-cuff method before sacrifice at 18 months. Glucose, total cholesterol, HDL, triglyceride and CRP were assessed in blood and eNOS, endothelin-1, iNOS and sirtuins were detected by immunofluorescence in the penis sections; eNOS, endothelin-1, iNOS, SIRT2-4 and SIRT6-7 were semi-quantified by western blotting in tissue homogenates. MicroRNA-155 was quantified using RT-PCR in formalin-fixed paraffin embedded sections. To compare the studied variables, two-tail student t test was used.

Results

Atorvastatin promotes eNOS expression and is more efficient than ER or exercise in the control of hyperlipidemia and inflammation. Among the studied sirtuins, detected for the first time in the erectile tissue of the aged rat, SIRT2 aligns with eNOS expression. Both proteins exhibit over-expression in animals with combined exercise, atorvastatin and ER. Analysis of microRNA-155 expression also suggests its intervention in the regulation of eNOS expression. ER, particularly when combined with atorvastatin, was able to reverse the increase of iNOS and endothelin-1 in high-fat fed rats.

Conclusions

The present results indicate that the association of ER, atorvastatin and exercise is more efficient than isolated interventions in the prevention of endothelial dysfunction.

A role of the endothelial nitric oxide system in acute renal colic caused by ureteral stone

BACKGROUND AND AIMS

Endothelial nitric oxide synthase gene polymorphisms play a role in some pathophysiological processes. In this study, the possible effects of endothelial nitric oxide synthase gene polymorphisms on ureteral stone disease in patients who were admitted to the emergency department with severe pain due to renal colic are examined.

MATERIALS AND METHODS

The study groups were designed as controls and patients. The control group was formed from the healthy volunteers who applied to the blood center next to the emergency service. The patient group comprised patients who were diagnosed with ureteral stone disease with severe pain. All of the genetic studies were based on extracted peripheral blood samples using the necessary procedures from the Genome and Stem Cell Center at Erciyes University (GENKOK). The data were analyzed with SPSS (IBM, ver 20, United Sate).

RESULTS

The study group comprised 62 females and 138 males, and the control group comprised 64 females and 136 males. All of the stones that caused renal colic were found to be localized in the ureters and the ureterovesical junction. The genotypes of the intron 4 polymorphism were found to be as follows: 4a/4a in 10 people, 4b/4a in 115, and 4b/4b in 275 people. The GG genotype of the eNOS-G894T polymorphism was found in 108 patients in the study group and in117 of the healthy individuals. There was no statistically significant difference between the two groups regarding these data.

CONCLUSION

Although this study is the first in the literature to examine the relationship between renal colic and endothelial nitric oxide synthase gene polymorphisms, our study demonstrated that no relation was found.

Improvement of erectile dysfunction by the active pepide from Urechis unicinctus by high temperature/pressure and ultra - wave assisted lysis in Streptozotocin Induced Diabetic Rats

Introduction:

We investigate the effect of active peptide from Urechis unicinctus (UU) by high temperature/pressure and ultra-wave assisted lysis on erectile dysfunction in streptozotocin-induced diabetic rats.

Materials and Methods:

Forty 12-week-old Sprague-Dawley rats were used in this study. Diabetes was induced by a one-time intraperitoneal injection of streptozotocin (50mg/kg). One week later, the diabetic rats were randomly divided into four groups: normal control, untreated diabetes control, and groups treated with 100 or 500mg/kg/d UU peptide. Rats were fed with UU peptide by intragastric administration for 8 weeks. After 8 weeks, penile hemodynamic function was evaluated in all groups by measuring the intracavernosal pressure after electrostimulating the cavernous nerve. Nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) activities were measured and endothelial nitric oxide synthase (eNOS) and neuronal NOS (nNOS) protein expression was determined by Western blot.

Results:

Maximum intracavernosal pressure in diabetic control rats decreased significantly compared to normal control rats, and was increased significantly compared to untreated diabetic rats after UU peptide supplementation. Treatment with the higher dose of UU peptide significantly increased the NO and cGMP levels compared with the diabetic control group. Decreased activity and expression eNOS and nNOS were found in the diabetic rats compared with the normal control group. Decreased eNOS and nNOS in diabetic rats were improved by UU peptide administration.

Conclusions:

Active peptide from UU ameliorates erectile function in a streptozotocin induced diabetic rat model of erectile dysfunction.

Non-nitric oxide based metallovasodilators: synthesis, reactivity and biological studies

There is an increasing number of compounds developed to target one or more pathways involved in vasodilation. Some studies conducted with azaindole and indazole derivatives showed cardiovascular activity associated with these compounds. Fast and easy structural modification of these organic molecules can be achieved using metal complexes promoting a much larger spatial change than organic strategies, potentially leading to novel drugs. Here, we have prepared a series of complexes with a formula cis-[RuCl(L)(bpy)(2)]PF(6), where L = 7-azaindole (ain), 5-azaindole (5-ain), 4-azaindole (4-ain), indazole (indz), benzimidazole (bzim) or quinoline (qui), which were characterized by spectroscopic and electrochemical techniques (CV, DPV). These compounds showed reasonable stability exhibiting photoreactivity only at low wavelength along with superoxide scavenger activity. Cytotoxicity assays indicated their low activity preliminarily supporting in vivo application. Interestingly, vasodilation assays conducted in rat aorta exhibited great activity that largely improved compared to free ligands and even better than the well-studied organic compound (BAY 41-42272), with IC(50) reaching 55 nM. These results have validated this strategy opening new opportunities to further develop cardiovascular agents based on metallo-bicyclic rings.

Impaired neuronal nitric oxide synthase-mediated vasodilator responses to mental stress in essential hypertension

Neuronal NO synthase (nNOS) regulates blood flow in resistance vasculature at rest and during mental stress. To investigate whether nNOS signaling is dysfunctional in essential hypertension, forearm blood flow responses to mental stress were examined in 88 subjects: 48 with essential hypertension (42±14 years; blood pressure, 141±17/85±15 mm Hg; mean±SD) and 40 normotensive controls (38±14 years; 117±13/74±9 mm Hg). A subsample of 34 subjects (17 hypertensive) participated in a single blind 2-phase crossover study, in which placebo or sildenafil 50 mg PO was administered before an intrabrachial artery infusion of the selective nNOS inhibitor S-methyl-l-thiocitrulline (SMTC, 0.05, 0.1, and 0.2 μmol/min) at rest and during mental stress. In a further subsample (n=21) with an impaired blood flow response to mental stress, responses were measured in the presence and absence of the α-adrenergic antagonist phentolamine. The blood flow response to mental stress was impaired in hypertensive compared with normotensive subjects (37±7% versus 70±8% increase over baseline; P<0.001). SMTC blunted responses to mental stress in normotensive but not in hypertensive subjects (reduction of 40±11% versus 3.0±14%, respectively, P=0.01, between groups). Sildenafil reduced the blood flow response to stress in normotensive subjects from 89±14% to 43±14% (P<0.03) but had no significant effect in hypertensive subjects. Phentolamine augmented impaired blood flow responses to mental stress from 39±8% to 67±13% (P<0.02). Essential hypertension is associated with impaired mental stress-induced nNOS-mediated vasodilator responses; this may relate to increased sympathetic outflow in hypertension. nNOS dysfunction may impair vascular homeostasis in essential hypertension and contribute to stress-induced cardiovascular events.

Effect of short- and long-term sildenafil treatment on erectile dysfunction in rats with partial bladder outlet obstruction

AIM

Lower urinary tract symptoms (LUTS) and erectile dysfunction (ED) are frequent problems in older men worldwide. We evaluated the effect of short- and long-term sildenafil treatment on erectile function in rats with surgically induced partial bladder outlet obstruction (PBOO).

METHODS

A total of 60 male Sprague-Dawley rats were randomized in five groups: (1) control (sham-operated); (2) PBOO for 3 weeks; (3) PBOO for 6 weeks; (4) sildenafil (1.5 mg/rat/day) treated PBOO for 3 weeks; and (5) sildenafil treated PBOO for 6 weeks. We assessed erectile function by measuring intracavernous pressures (ICP), mean arterial pressure (MAP) and total ICP after cavernous nerve stimulation. Corpus cavernous smooth muscle (CCSM) strips were isolated and evaluated for relaxation responses using organ-bath preparation. Neuronal nitric oxide synthase (nNOS) expression was determined immunohistochemically.

RESULTS

Experimental PBOO at 3 and 6 weeks showed decreased erectile response based on ICP/MAP ratio, total ICP and decreased expression of nNOS, which returned to normal after prolonged daily treatment with sildenafil. CCSM strips from PBOO rats displayed reduced relaxation responses to both electrical field stimulation (EFS) and acetylcholine (ACh) as well as nNOS enzyme intensity when compared to untreated PBOO group, which was reversed by treatment with sildenafil for 6 weeks.

CONCLUSIONS

Daily sildenafil treatment prevents development of ED in PBOO rats in a time dependent manner. Further studies are needed to explore the effectiveness of sildenafil in patients with BPH/LUTS in association with ED.

Effect of avanafil on rat and human corpus cavernosum

We compared the activity of a new phosphodiesterase-5 inhibitor (PDE5i) avanafil with sildenafil and tadalafil in human and rat corpus cavernosum (CC) tissues. The effect of avanafil with several inhibitors and electrical field stimulation (EFS) was evaluated on CC after pre-contraction with phenylephrine. With the PDE5i, sildenafil and tadalafil, concentration-response curves were obtained and cyclic guanosine monophosphate (cGMP) levels were measured in tissues. Avanafil induced relaxation with maximum response of 74 ± 5% in human CC. This response was attenuated by NOS inhibitor and soluble guanylate cyclase (sGC) inhibitor. Avanafil potentiated relaxation responses to acetylcholine and EFS in human CC and enhanced SNP-induced relaxation and showed 3-fold increase in cGMP levels. When compared with sildenafil, avanafil and tadalafil were effective at lower concentrations in human CC. In addition, Sprague-Dawley rats underwent in vivo intracavernosal pressure (ICP) and mean arterial pressure (MAP) measurements. Avanafil increased ICP/MAP that was enhanced by SNP and cavernous nerve (CN) stimulation in rat CC tissues. Also avanafil showed maximum relaxation response of 83 ± 7% in rat CC with 3-fold increase in cGMP concentration. Taken together, these results of our in vivo and in vitro studies in human and rat suggest that avanafil promotes the CC relaxation and penile erection via NO-cGMP pathway.

Gas what: NO is not the only answer to sexual function

The ability to get and keep an erection is important to men for several reasons and the inability is known as erectile dysfunction (ED). ED has started to be accepted as an early indicator of systemic endothelial dysfunction and subsequently of cardiovascular diseases. The role of NO in endothelial relaxation and erectile function is well accepted. The discovery of NO as a small signalling gasotransmitter led to the investigation of the role of other endogenously derived gases, carbon monoxide (CO) and hydrogen sulphide (H2 S) in physiological and pathophysiological conditions. The role of NO and CO in sexual function and dysfunction has been investigated more extensively and, recently, the involvement of H2 S in erectile function has also been confirmed. In this review, we focus on the role of these three sister gasotransmitters in the physiology, pharmacology and pathophysiology of sexual function in man, specifically erectile function. We have also reviewed the role of soluble guanylyl cyclase/cGMP pathway as a common target of these gasotransmitters. Several studies have proposed alternative therapies targeting different mechanisms in addition to PDE-5 inhibition for ED treatment, since some patients do not respond to these drugs. This review highlights complementary and possible coordinated roles for these mediators and treatments targeting these gasotransmitters in erectile function/ED.

Oral L-citrulline supplementation improves erectile function in rats with acute arteriogenic erectile dysfunction

INTRODUCTION

Oral L-citrulline supplementation increases serum L-arginine levels more efficiently than L-arginine itself and increases nitric oxide (NO) production.

AIM

To investigate whether oral L-citrulline supplementation improves erectile function in rats with acute arteriogenic erectile dysfunction (ED).

METHODS

We divided 8-week-old male Wistar-ST rats into 3 groups: sham-operated rats (control group), arteriogenic ED rats who underwent ligation of both internal iliac arteries (ligation group), and arteriogenic ED rats receiving oral 2% L-citrulline water supplementation (citrulline group). Citrulline water was given to arteriogenic ED rats for 3 weeks from 1 week after surgery. Erectile function was evaluated by maximum intracavernous pressure/mean arterial pressure (ICP/MAP) ratios via cavernous nerve stimulation at 4 weeks after surgery. Then, the penises were resected, stained with Masson's trichrome, and observed microscopically. Serum nitrogen oxides (NOx) levels were measured by high-performance liquid chromatography. Bonferroni's multiple t-test was used for statistical analysis.

MAIN OUTCOME MEASURES

The main outcome measures were changes in ICP/MAP, smooth muscle (SM)/collagen ratios, and NOx levels following L-citrulline supplementation.

RESULTS

The ICP/MAP ratio in the ligation group was significantly lower than that in the control group (P<0.05), denoting ED. The ICP/MAP ratio of the citrulline group was significantly higher than that of the ligation group (P<0.05), indicating ED amelioration. Levels of NOx in the ligation group were significantly lower than in the control group (P<0.05), while those in the citrulline group were significantly higher than in the ligation group (P<0.05). SM/collagen ratios in the ligation group were significantly lower than in the control group (P<0.05), while ratios in the citrulline group were significantly higher than those in the ligation group (P<0.05).

CONCLUSIONS

Oral L-citrulline supplementation improved ICP/MAP and SM/collagen ratios and increased NOx. Therefore, oral L-citrulline supplementation might be a useful novel therapy for acute arteriogenic ED.

L-NAME in the cardiovascular system - nitric oxide synthase activator?

L-arginine analogues are widely used inhibitors of nitric oxide synthase (NOS) activity both in vitro and in vivo, with N(ω)-nitro-L-arginine methyl ester (L-NAME) being at the head. On the one hand, acute and chronic L-NAME treatment leads to changes in blood pressure and vascular reactivity due to decreased nitric oxide (NO) bioavailability. However, lower doses of L-NAME may also activate NO production via feedback regulatory mechanisms if administered for longer time. Such L-NAME-induced activation has been observed in both NOS expression and activity and revealed considerable differences in regulatory mechanisms of NO production between particular tissues depending on the amount of L-NAME. Moreover, feedback activation of NO production by L-NAME seems to be regulated diversely under conditions of hypertension. This review summarizes the mechanisms of NOS regulation in order to better understand the apparent discrepancies found in the current literature.

PDE5 inhibitors: targeting erectile dysfunction in diabetics

Erectile dysfunction (ED) is strongly linked to cardiovascular disease (CVD), especially in diabetics. ED is associated with deleterious changes in the overall vasculature and is recognized as an indicator of higher risk for adverse cardiovascular events. Endothelial dysfunction, vascular smooth muscle changes and increased fibrosis are indicated as major players in both ED and CVD. ED in diabetics is more refractory to acute treatment with phosphodiesterase-5 (PDE5) inhibitors (Viagra, Cialis, Levitra, Zydena) than in non-diabetics, but recent studies indicate that chronic administration of these drugs improves endothelial function, preserves vascular smooth muscle and decreases fibrotic changes. Use of PDE5 inhibitors in pre-diabetic and diabetic men may protect cardiovascular health, including vascular function in penile tissues.

Increased expression of insulin-like growth factor-binding protein-3 is implicated in erectile dysfunction in two-kidney one-clip hypertensive rats after propranolol treatment

This study aimed to investigate the role of insulin-like growth factor-binding protein-3 (IGFBP-3) in erectile dysfunction (ED) in two-kidney one-clip (2K-1C) hypertensive rats treated with the β-blocking agent propranolol. Adult male Wistar rats were randomly divided into three groups: a normal control group, a hypertensive control group and a propranolol treatment group (n=9). After 4 weeks of propranolol treatment, intracavernous pressure (ICP) responses to electrical stimulation of the cavernous nerves were evaluated. The expression of IGFBP-3 and insulin-like growth factor-1 (IGF-1) mRNA and protein in the rat cavernous tissue were detected by quantitative real-time PCR and Western blot, respectively. The concentration of cyclic guanosine monophosphate (cGMP) in the cavernous tissue was determined by enzyme-linked immunosorbent assay (ELISA). Cavernosal pressure in response to cavernous nerve stimulation was decreased 4 weeks after propranolol treatment (P<0.01, compared to the hypertensive control group). IGFBP-3 mRNA and protein expression was increased in the propranolol treatment group compared to the hypertensive control group (P<0.01), whereas IGF-1 expression was decreased in the propranolol treatment group compared to the hypertensive control group (P<0.01). In addition, cavernous cGMP concentration was decreased in the propranolol treatment group compared to the hypertensive control group (P<0.01). Taken together, these results suggest that the upregulation of IGFBP-3 may play a role in the development of ED in hypertensive rats.

Long-term oral treatment with BAY 41-2272 ameliorates impaired corpus cavernosum relaxations in a nitric oxide-deficient rat model

OBJECTIVE

• To investigate the potential beneficial effects of 4-week oral treatment with 5-cyclopropyl-2-[1-(2-fluoro-benzyl)-1Hpyrazolo[3,4-b]pyridin-3-yl]-pyrimidin-4-ylamine (BAY 41-2272), a nitric oxide (NO)-independent soluble guanylate cyclase activator, on impaired rat corpus cavernosum relaxations in NO-deficient rats.

MATERIAL AND METHODS

• Male Wistar rats were divided into four groups: Control, N (G)-nitro-L- arginine methyl ester (L-NAME; 20 mg/rat/day), BAY 41-2272 (20 mg/kg/day) and L-NAME + BAY 41-2272. • Rats were treated with L-NAME concomitantly with BAY 41-2272 for 4 weeks. • Concentration-response curves to acetylcholine (ACh) and sodium nitroprusside (SNP), along with the nitrergic relaxations (1-32 Hz) were obtained in rat corpus cavernosum (RaCC). • The RaCC contractile responses to the α₁ -adrenoceptor agonist phenylephrine (PE) were obtained.

RESULTS

• Acetylcholine (0.01-1000 µmol/L) produced concentration-dependent relaxing responses in RaCC that were significantly enhanced (P < 0.05) in BAY 41-2272-treated rats. • The ACh-induced relaxations were largely reduced in L-NAME-treated rats, and co-treatment with BAY 41-2272 failed to significantly modify these impaired relaxations. • The SNP-induced relaxations were modified neither by L-NAME nor by co-treatment with BAY 41-2272. • The nitrergic relaxations were significantly amplified in BAY 41-2272-treated rats (at 16 and 32 Hz). A significant reduction in the nitrergic relaxations was observed in L-NAME-treated rats, an effect largely restored by co-treatment with BAY 41-2272. • The contractile RaCC responses produced by PE (0.001-100 µmol/L) were significantly higher (P < 0.05) in L-NAME-treated rats, and co-treatment of L-NAME with BAY 41-2272 nearly restored these enhanced contractile responses.

CONCLUSION

• Four-week therapy with BAY 41-2272 prevents the impaired corpus cavernosum relaxations of rats treated chronically with L-NAME, indicating that accumulation of cyclic guanosine monophosphate into erectile tissue counteracts the NO deficiency.