Lead acetate versus cadmium sulfate in the modulation of main physiological pathways controlling detrusor muscle contractility in rat.

Heavy metals have a deleterious effect on lower urinary tract functions. Scant data has been reported about metals' effect on altering detrusor muscle contractility. Rats were given lead acetate (3, 30 mg/kg), cadmium sulfate (0.1, 1 mg/kg) or ferrous sulfate-iron overload-(3, 30 mg/kg), in a subacute toxicity study (21 days, ip). In-vitro tension experiments were conducted using isolated rat detrusor muscle. Measurement of heavy metal concentrations in blood and tissue homogenates was performed, as well as histopathological examinations. Subacute toxicity induced by treatment with lead and cadmium was manifested as a decrease in EFS, ACh, and ATP-mediated contraction of isolated detrusor muscle. Iron overload only decreased EMAX of EFS and ACh-mediated contraction. Lead (30 mg/kg) caused an upward shift in the dose response curve of isoprenaline-induced relaxation, with a significant decrease in EMAX. Lead (30 mg/kg) or cadmium (1 mg/kg) inhibited adenosine (10-5 M)-induced relaxation. Comparisons to control tissues showed a selective accumulation of metals in the detrusor muscle. Histopathological examinations revealed edema and inflammation in the urinary bladder. Directly added lead (10 mM) inhibited detrusor muscle contraction in-vitro, and its effect was decreased in presence of atropine, and potentiated in presence of TEA, L-NAME, or MB. Cadmium's (0.1 mM) inhibitory effect was reduced in presence of nifedipine or trifluoperazine. In conclusion, lead, cadmium, or iron induce detrusor hypoactivity: The inhibitory effect of lead may be mediated by modulating muscarinic receptors but not the K+/NO/cGMP pathway, whereas cadmium inhibitory effect may be mediated by inhibiting the Ca2+/calmodulin pathway.

Hypoactivity of rat detrusor muscle in a model of cystitis: exacerbation by non-selective COX inhibitors and amelioration by a selective DP1 receptor antagonist.

Various studies have confirmed that prostaglandins (PG) alter the bladder motor activity and micturition reflex in both human and animals. However, no sufficient data is reported about the effect of cyclooxygenase (COX) inhibitors neither in normal bladder physiology nor in pathological conditions. This study aims to compare the potential effects of some COX inhibitors with varying COX-1/COX-2 selectivities (indomethacin, ketoprofen, and diclofenac) with that of the selective COX-2 inhibitor (DFU) on bladder function. The role played by some PGs and their receptors in controlling detrusor muscle function in normal condition and in cystitis is also studied. Organ bath experiments were performed using isolated rat detrusor muscle. Direct and neurogenic contractions were induced using ACh and electric stimulation (EFS), respectively. A model of hemorrhagic cystitis was induced by single injection of cyclophosphamide (300 mg/kg) in rats, and confirmed by histophathological examination. Results are expressed as mean ± SEM of 5-9 rats. Alprostadil and iloprost (1 nM- 10 µM) concentration-dependently potentiated ACh (100 µM)- and EFS (4 Hz)-induced contraction, with maximum potentiation of 40.01 ± 5.29 and 27.59 ± 6.64%, respectively, in case of ACh contractions. In contrast, ONO-AE1-259 (selective EP2 agonist, 1 nM-10 µM) inhibited muscle contraction. SC51322 (EP1-antagonist, 10 µM) and RO1138452 (IP antagonist, 10 µM) inhibited both direct and neurogenic responses. Hemorrhagic cystitis reduced both ACh and EFS responses as well as the potentiatory effect of iloprost and the inhibitory effect of RO1138452 on ACh contractions. ONO-AE3-237 (DP1 antagonist, 1 µM) significantly potentiated contractions in cystitis but showed no effect in normal bladder. A significant inhibition of contractile response was observed in presence of indomethacin, ketoprofen, and diclofenac at all tested concentrations (20, 50, and 100 µM). Highest effect was induced by diclofenac. The effect of these COX inhibitors on EFS contractions was intensified in case of cystitis, indomethacin being the most potent. Atropine (1 nM) significantly reduced indomethacin effect on ACh contraction only in normal rats. On the other hand, DFU (10-6 M) significantly potentiated the contractile effect of ACh in case of cystitis although it showed no effect in normal rats. EP1 receptors seem to play an important role in rat bladder contractility. DP1 receptors as COX-2, on the other hand, gain an important role only in case of cystitis. The use of non-selective COX inhibitors in cystitis may be associated with bladder hypoactivity; selective COX-2 inhibitors may be a safer option.

Neuronal Voltage Gated Potassium Channels May Modulate Nitric Oxide Synthesis in Corpus Cavernosum.

Potassium channels (K+Ch) in corpus cavernosum play an important role in the regulation of erection. Nitric oxide (NO) acts through opening of K+Ch leading to hyperpolarization and relaxation. Aim : This study aims to update knowledge about the role of voltage-gated K+Ch (KV) channels in erectile machinery and investigate their role in the control of NO action &/or synthesis in the corpus cavernosum. Methods : Tension studies using isolated rabbit corpus cavernosum (CC) strips and rat anococcygeus muscle were conducted. Results are expressed as mean ± SEM. Results : Electric field stimulation (EFS, 2-16 Hz) evoked frequency-dependent relaxations of the PE (phenylephrine)-precontracted CC strips. At 2 Hz, EFS-induced relaxation amounted to 73.17 ± 2.55% in presence 4-AP (10-3 M) compared to 41.98 ± 1.45% as control. None of the other selective K+Ch blockers tested inhibited EFS-induced relaxation. 4-AP (10-3M) significantly attenuated ACh-induced relaxation of rabbit CC where dose-response curve was clearly shifted upward, and attenuated SNP- induced relaxation, for example, to 49.28 ± 4.52% compared to 65.53 ± 3.01% as control at 10-6 M SNP. The potentiatory effect of 4-AP on EFS was abolished or reversed in presence of N G -nitro-L-arginine (L-NNA, non-selective nitric oxide synthase inhibitor, 10-5M, and 2 × 10-4M). Same results were observed in rat anococcygeus muscle which is a part of the erectile machinery in rats. Conclusion : This study provides evidence for the presence of prejunctional voltage-gated K+Ch in CC, the blockade of which may increase the neuronal synthesis of NO.

Different mechanisms for lead acetate, aluminum and cadmium sulfate in rat corpus cavernosum.

INTRODUCTION: Some heavy metals show adverse vascular and neurological effects, however, their effect on erection is underestimated. This study aims to investigate the effect of Pb, Cd and Al on erectile function and their potential mechanism of action in rats. METHODS: Measurement of intracavernosal pressure/mean arterial pressure (ICP/MAP) changes elicited by electrical stimulation of cavernous nerve in anesthetized rats treated with Pb-acetate, Al-sulfate, or Cd-sulfate acutely, and subacutely for 7 days. Serum creatinine, testosterone, TBARs, GSH levels and metal accumulation in corpus cavernosum were measured. RESULTS: Pb, Al and Cd significantly reduced ICP/MAP in rats after acute (2,10-2,10 and 1,3 mg/kg respectively) and sub-acute (3, 3, and 1mg/kg/day respectively) treatments. They selectively accumulated in the corpus cavernosum reaching 25.107 ± 2.081 µg/g wet weight for Pb, 1.029 ± 0.193 for Cd, 31.343 ± 1.991 for Al, compared to 7.084 ± 1.517, 0.296 ± 0.067, and 8.86 ± 1.115 as controls respectively. Serum creatinine levels were not altered. Cd and Al significantly reduced testosterone level to 0.483 ± 0.059 and 0.419 ± 0.037 ng/ml respectively compared to 0.927 ± 0.105 ng/ml as control. Aluminum elevated TBARs significantly by 27.843%. The acute anti-erectile action of Pb was blocked by non-selective NOS and GC inhibitors and potassium channel blocker. Lead also masked the potentiatory effect of l-arginine and diazoxide on ICP/MAP. No interaction with muscarinic or nicotinic modulators was observed. CONCLUSIONS: Pb, Cd and Al show anti-erectile effect independent on renal injury. They don not modulate cholinergic nor ganglionic transmission in corpus cavernosum. Pb may inhibit NO/cGMP/K+channel pathway. The effect of Cd and Al but not Pb seems to be hormonal dependent.

Ex vivo relaxations of pulmonary arteries induced by prostacyclin mimetics are highly dependent of the precontractile agents.

Prostacyclin (PGI2) mimetics (iloprost, treprostinil) are potent vasodilators (primarily via IP-receptor activation) and major therapeutic interventions for pulmonary hypertension (PH). Increased plasma levels of endothelin (ET-1), thromboxane (TxA2) and catecholamines have been demonstrated from patients with PH. In this study, we aimed to compare relaxant effects of iloprost and treprostinil on human (HPA) and rat pulmonary arteries precontracted with either ET-1, thromboxane (U46619) or an α-adrenergic receptor agonist (Norepinephrine, NE or phenylephrine, PE). Treprostinil and iloprost induced vasorelaxation of HPA precontracted with NE, ET-1 or U46619. We obtained greater relaxation response and sensitivity to treprostinil when ET-1 or U46619 were used to induce the precontraction in comparison to NE. In contrast, iloprost showed less relaxation response and sensitivity in HPA precontracted with U46619 versus NE. In the rat, treprostinil and iloprost induced vasorelaxation of pulmonary arteries precontracted with PE and U46619 but minimally with ET-1. However, in rat pulmonary arteries, PE-induced precontractions were comparatively low amplitude. Our study showed that the ex vivo relaxation or sensitivity of pulmonary arteries induced by PGI2 mimetics is highly dependent on both the pre-contraction agent and the species. To best extrapolate to effects on human tissue, our results suggest that U46619 is the appropriate contractile agent for assessing the relaxant effect of PGI2 mimetics in rat pulmonary arteries. Finally we suggest that in PH patients with high plasma concentration of TxA2, treprostinil (not iloprost) would be a preferential treatment. On the other hand, if the ET-1 plasmatic level is high, either treprostinil or iloprost will be effective.

Evaluation of l-arginine on kidney function and vascular reactivity following ischemic injury in rats: protective effects and potential interactions.

BACKGROUND: There is an interaction between many cell types involved in the pathophysiology of ischemic acute renal failure. Nitric oxide (NO) precursors, especially l-arginine, may have protective effects on tissue ischemia/reperfusion injury (IRI); however, their molecular mechanisms are unclear. In the present study, the interaction between l-arginine, cyclo-oxygenase (COX)-2 and reactive oxygen species (ROS) in the pathogenesis of ischemic acute renal failure was investigated. METHODS: Ischemia/reperfusion injury model in rats was used and various biochemical parameters examined. The rat isolated aortic rings served as model for hypoxia/reoxygenation where endothelium dependent and independent relaxations were exerted. RESULTS: Pre-treatment of rats subjected to IRI with l-arginine (125mg/kg) significantly reduced kidney MDA levels, elevated kidney SOD activity, GSH level and total NO levels at 24 and 48h after reperfusion. Kidney COX-2 level was only different in the l-arginine-treated group 48h after reperfusion compared to the IRI group. Pre-treatment with l-arginine (10(-2)M) alone or in combination with celecoxib significantly potentiated the acetylcholine (Ach)-induced relaxations in control and hypoxic rings. The effect of the combination was synergistic only in hypoxic rings. Addition of ascorbic acid to the celecoxib-arginine combination did not produce further potentiation. Sodium nitroprusside-induced relaxations in control and hypoxic rings were potentiated by l-arginine or celecoxib-arginine combination but not by ascorbic acid. CONCLUSIONS: The protective effect of l-arginine may result from the interaction between NO and ROS and increased NO bioavailability. The protective effects of combined celecoxib and l-arginine against IRI could be attributed to their antioxidant activity which exceeded that of ascorbic acid.

Lead acetate may cause erectile dysfunction by modulating NO/cGMP pathway in rat corpus cavernosum.

Despite the fact that metal toxicity has been widely reported in industrial toxicological studies, very little has been reported about the effect of lead exposure on erectile function. This study investigated the effect of lead on erectile function in rats and aimed to preliminarily test the mechanisms by which it might affect erection. Rats were injected with lead acetate (0.25-2 mg/kg) intraperitoneally for 21 days. Intracavernosal pressure/mean arterial pressure (ICP/MAP) next to nerve stimulation; nitrite/nitrate; malonaldehyde; and reduced glutathione levels and superoxide dismutase activity in the corpus cavernosum, kidney, and brain were measured in addition to creatinine, urea, and testosterone. For acute studies, rats were injected intravenously with lead acetate, and then ICP/MAP was recorded for 45 min. Subacute treatment significantly reduced erection with significant elevation of malonaldehyde and reduction of nitrite/nitrate levels in the corpus cavernosum. In acute studies, lead (2 and 5 mg/kg) reduced neurogenic erections by 28.42 ± 3.76 and 96.84 ± 8.52%, respectively, an effect that was masked in the presence of NG-nitro-L-arginine, tetraethyl ammonium, or methylene blue, but not zinc protoporphyrine, and reversed by vitamin C and partially by sildenafil. Lead acetate may inhibit the erectile process in rats. Besides its prooxidant effect and consequent inactivation of nitric oxide, lead may negatively modulate the action of nitric oxide on guanylate cyclase and potassium channels.

Effect of chronic low-dose tadalafil on penile cavernous tissues in diabetic rats.

OBJECTIVE: To assess the effect of chronic low-dose administration of tadalafil (Td) on penile cavernous tissue in induced diabetic rats. METHODS: The study investigaged 48 adult male albino rats, comprising a control group, sham controls, streptozotocin-induced diabetic rats, and induced diabetic rats that received Td low-dose daily (0.09 mg/200 g weight) for 2 months. The rats were euthanized 1 day after the last dose. Cavernous tissues were subjected to histologic, immunohistochemical, morphometric studies, and measurement of intracavernosal pressure and mean arterial pressure in anesthetized rats. RESULTS: Diabetic rats demonstrated dilated cavernous spaces, smooth muscles with heterochromatic nuclei, degenerated mitochondria, vacuolated cytoplasm, and negative smooth muscle immunoreactivity. Nerve fibers demonstrated a thick myelin sheath and intra-axonal edema, where blood capillaries exhibited thick basement membrane. Diabetic rats on Td showed improved cavernous organization with significant morphometric increases in the area percentage of smooth muscles and elastic tissue and a significant decrease of fibrous tissue. The Td-treated group showed enhanced erectile function (intracavernosal pressure/mean arterial pressure) at 0.3, 0.5, 1, 3, and 5 Hz compared with diabetic group values at the respective frequencies (P <.05) that approached control values. CONCLUSION: Chronic low-dose administration of Td in diabetic rats is associated with substantial improvement of the structure of penile cavernous tissue, with increased smooth muscles and elastic tissue, decreased fibrous tissue, and functional enhancement of the erectile function. This raises the idea that the change in penile architecture with Td treatment improves erectile function beyond its half-life and its direct pharmacologic action on phosphodiesterase type 5.

Combined effect of sildenafil and guanethidine, propranolol or verapamil on erectile function in rats.

OBJECTIVES: This study aims to further elucidate the role of adrenergic transmission in erection and to highlight whether adrenergic transmission in the penis modulates sildenafil's action. METHODS: Measurement of intracavernosal pressure in the anesthetized rat model. KEY FINDINGS: Guanethidine (3 and 6 mg/kg) potentiated intracavernosal pressure/mean arterial pressure (ICP/MAP) rises in response to cavernous nerve stimulation by 4.375 ± 0.425 and 18.375 ± 1.085% respectively. Propranolol did the opposite. In presence of guanethidine, sildenafil (0.01, 0.1 and 1 mg/kg) potentiated ICP/MAP responses by 81.571 ± 4.918%, 147.83 ± 10.864% and 279.285 ± 23.053% at 1 Hz compared to 22.277 ± 2.139%, 123.571 ± 8.443% and 186.25 ± 13.542% respectively in the absence of guanethidine. Propranolol inhibited the effect sildenafil at all frequencies of stimulation. Verapamil exhibited a pro-erectile action and potentiated the effect of sildenafil (0.01, 0.1 and 1 mg/kg) on erectile responses corresponding to 85.25 ± 6.716%, 146 ± 11.288% and 221.571 ± 19.032% respectively compared to 26.011 ± 1.911%, 87.142 ± 8.73% and 182.2 ± 16.921% in its absence. CONCLUSIONS: This study provides functional evidence that inhibition of sympathetic tone peripherally results in enhancement of erectile function. ß-adrenergic receptors seem to play an important role in erection. The combination of sildenafil and guanethidine or verapamil could have a potential advantage on erectile function but propranolol may mask the effect of sildenafil on erectile function.

Evaluation of vitamin E in the treatment of erectile dysfunction in aged rats.

AIMS: The present study aims to elucidate the role of oxidative stress in erectile dysfunction associated with aging and to investigate the effect of treatment with vitamin E in this respect. MAIN METHODS: Rats were divided into four groups: young (3-month-old), aged rats (18-month-old), aged rats given 80 IU of vitamin E/rat/day for 21-days, aged rats given 5mg/kg of sildenafil/day for 21-days. Intracavernosal pressure/mean arterial pressure (ICP/MAP), nitric oxide production, TBARS, GSH levels and SOD activity in corpus cavernosum were measured. KEY FINDINGS: Significant decrease in ICP/MAP was observed in aged rats at both low and high frequency of stimulation. Significant increase in ICP/MAP was observed in aged rats treated with vitamin E over the range of 0.8 to 5 Hz but young control values were not restored. Percentage potentiation of ICP/MAP than aged group at 0.8 Hz was 326±41.3% and 897±72.2% for vitamin E and sildenafil respectively. Decreased levels of NO(2)/NO(3) and SOD activity in the penile tissue observed with aging were elevated back to control by either vitamin E or sildenafil. Penile concentration of TBARS was 20.86±0.83 for aged rats vs. 11.39±0.79 nmol/g tissue for young controls. Both vitamin E and sildenafil reduced penile TBARS in aged rats. SIGNIFICANCE: This study proves that antioxidant therapy with vitamin E ameliorates the age-associated erectile dysfunction. Sildenafil may exert some antioxidant properties which add to the advantages of its long-term use. The effect of combinations of low-dose sildenafil and vitamin E on age-associated erectile dysfunction merits to be studied.

Interaction between nitric oxide and dopaminergic transmission in the peripheral control of penile erection.

As the peripheral role of dopamine in the mediation of penile erection was recently identified, its potential role in the modulation of NO action and whether D1 or D2 receptors are involved in this potential modulation was investigated. The isolated rabbit corpus cavernosum and measurement of intracavernosal pressure in the anesthetized rat model were used. The selective D1 antagonist SCH23390 but not the D2 antagonist sulpiride reduced the inhibitory effect of N(G)-nitro-L-arginine (L-NNA) and the potentiatory effect of sildenafil on erectile responses. L-NNA did not change the inhibitory effect of SCH23390 or the potentiatory effect of apomorphine but enhanced the effect of high-dose fenoldopam on intracavernosal pressure. Similarly, fenoldopam produced 47.30 ± 6.89% potentiation of relaxation of corpus cavernosum in absence of L-NNA and 80 ± 9.34% potentiation in its presence at 3 Hz. The effect of sildenafil was greatly reduced by pretreatment with SCH23390 or sulpiride and completely abolished by their combination. This study supports the role played by D1 receptors peripherally in the control of penile erection. Absence of NO may potentiate the effect of D1 receptor on erection. Activation of D1 receptors may be involved in the synthesis of NO in the corpus cavernosum or may activate the role of NO in erection.

Functional inhibition of erectile process in rats by indomethacin.

OBJECTIVES: Despite the important role played by prostaglandins in the control of erection, the potential contribution of non-steroidal anti-inflammatory drugs in erectile dysfunction in experimental animals has not been investigated. We examined the effect of the selective COX-2 inhibitor, celexocib, and the non-selective COX-inhibitors, indomethacin and diclofenac on erectile process in vivo. METHODS: Erectile responses to electrical stimulation of the cavernous nerve in anesthetized male rats were recorded after single and repeated administration and intracavernosal pressure/mean arterial pressure (ICP/MAP) was calculated. The effect on blood pressure during erection and total plasma nitrite/nitrate level was also investigated. RESULTS: Single-dose administration of indomethacin significantly reduced erectile responses to electrical stimulation at all frequencies tested; 15 mg/kg further reduced ICP/MAP to 0.016 ± 0.005 compared to 0.064 ± 0.012 and 0.104 ± 0.035 for indomethacin (5 mg/kg) and control, respectively at 0.5 Hz. Longer-term treatment with indomethacin completely abolished erectile responses at low frequencies and significantly reduced ICP/MAP at higher frequencies, accompanied by significant reduction in total plasma nitrite/nitrate level. Diclofenac reduced erectile responses only at low frequencies in contrast to celexocib that failed to negatively affect erectile responses. CONCLUSION: Indomethacin, and to a lower extent diclofenac, may adversely affect erectile responses in rats.

A novel COX-2 inhibitor pyrazole derivative proven effective as an anti-inflammatory and analgesic drug.

The introduction of new COX-2 inhibitors with high efficacy and enhanced safety profile would be a great achievement in the development of anti-inflammatory drugs. This study was designed to screen and assess the anti-inflammatory and analgesic activities as well as some of the expected side effects of some pyrazole derivatives, newly synthesized as potential COX-2 inhibitors at the Faculty of Pharmacy, Alexandria University and compared to indomethacin and celecoxib. Twelve compounds were screened for their anti-inflammatory activity using carrageenan-induced paw oedema and cotton pellet granuloma tests. On the basis of their apparent anti-inflammatory activity, four compounds with different substitutions were selected for the evaluation of their analgesic activity using the formalin-induced hyperalgesia and hot-plate tests. Compound AD 532, ((4-(3-(4-Methylphenyl)-4-cyano-1H-pyrazol-1-yl)benzenesulfonamide)), showed very promising results. In the single-dose and subchronic toxicity studies, compound AD 532 showed no ulcerogenic effect and produced minimal effects on renal function. Furthermore, compound AD 532 was a less potent inhibitor of COX-2 in vitro than celecoxib, which may indicate lower potential cardiovascular toxicity. It is concluded that compound AD 532 appears to be a promising and safe option for the management of chronic inflammatory conditions. This study recommends more in-depth investigation into the therapeutic effects and toxicity profile of this compound including its cardiovascular toxicity.

Peripheral modulation of dopaminergic receptors affects erectile responses in rats.

Clinical observations have suggested that dopaminergic mechanisms are involved in the regulation of male sexual responses, including erection. Apomorphine was initially reported to exert its erectogenic effects by modifying central dopaminergic activity. This study aimed primarily at evaluating and investigating the effect of apomorphine on erectile functions in rats and its potential effects on the cardiovascular system, as well as the possible role of dopaminergic stimulation in the peripheral control of erection. Measurement of intracavernosal pressure changes elicited by electrical stimulation of the cavernosal nerve in anaesthetized rats and mating tests were used. SCH23390, the D1 receptor antagonist, attenuated penile response to electrical stimulation. Intravenous administration of apomorphine in low dose (100 microg/kg), but not in high dose, significantly potentiated erectile responses to electrical stimulation. Intracavernosally injected apomorphine (50 microg/kg) significantly potentiated the filling rate of the corpora cavernosa 5 min. after injection, and did not induce erection in absence of electrical stimulation. In addition, apomorphine amplified the male sexual and copulatory behaviour by reducing ejaculation, mount and intromission latencies, and significantly increasing the number of ejaculations per session. However, apomorphine produced rapid and long-lasting hypotension and potentiated the hypotension and tachycardia associated with nerve-stimulated penile erection. Our results suggest that D1-dopaminergic receptors may be functionally involved in the peripheral mediation of penile erection. Apomorphine may amplify sexual and copulatory behaviour and may also, by a complementary role, amplify neurogenically mediated erections by acting in the periphery.