一氧化氮——阴茎勃起机制研究中的新课题

一氧化氮──阴茎勃起机制研究中的新课题高冰，薛兆英，郭应禄阴茎勃起机制复杂，近十年来多数研究着重于勃起时血流动力学的改变，作为非肾上腺素能非胆碱能（ＮＡＮＣ）介质的肽能神经递质在勃起生理中起着一定的作用［１］。最近发现一氧化氮（ＮＯ）是一种强有力的内...     

NO对前列腺及阴茎勃起功能的调节作用

一氧化氮是一种不稳定的低分子有害气体 ,同时它又是一种生物活性物质 ,参与了多种疾病的病理生理过程。一氧化氮在体内由L 精氨酸在一氧化氮合成酶的作用下生成 ,作为一种非肾上腺能非胆碱能神经递质 ,对动物和人的生殖泌尿器官平滑肌张力起着重要的调节作用。本文简要介绍一氧化氮在体内的产生机制和分布 ,并着重概述一氧化氮对平滑肌舒张调节作用机理 ,及其在非手术治疗前列腺增生导致下尿路梗阻及改善阴茎勃起功能障碍方面的临床应用。     

一氧化氮及其合成酶与阴茎勃起调控

阴茎勃起起机制复杂，学说颇多。本文综述一氧化氮和一氧化氮合成酶的生物学特性及其在勃起生理中的作用。     

一氧化氮及其合成酶与阴茎勃起调控

阴茎勃起机制复杂，学说颇多。近年来，一种全新的阴茎勃起调控机理已被提出，即一氧化氮及其合成酶调控理论。本文综述一氧化氮（ｎｉｔｒｉｃｏｘｉｄｅ，ＮＯ）和一氧化氮合成酶（ｎｉｔｒｉｃｏｘｉｄｅｓｙｎｔｈａｓｅ，ＮＯＳ）的生物学特性及其在勃起生理中的作用。     

一氧化氮等神经递质与阴茎勃起关系的实验观察

为探讨阴茎勃起的神经调节机制，作者通过电刺激狗盆神经诱发阴茎勃起，选择硝普钠为一氧化氮（ＮＯ）的供体，研究了ＮＯ及其相关因素ｃＧＭＰ、ｃＡＭＰ和亚甲蓝在阴茎勃起过程中的作用，同时观察了胆碱能神经递质、窦内皮细胞在勃起中的作用。实验结果支持海绵体平滑肌松弛为胆碱能神经和非肾上腺非胆碱能（ＮＡＮＣ）神经递质所介导，ＮＯ或其释放物质是阴茎勃起的主要ＮＡＮＣ类神经递质的学说。该发现有助于临床解决阴茎勃起障碍的治疗。     

盆神经节海绵体内移植对双侧海绵体神经损伤后大鼠阴茎勃起功能的影响

目的　研究双侧海绵体神经离断后 ,自体盆神经节海绵体内移植对大鼠阴茎勃起功能的影响。方法　将 2 6只雄性SD大鼠 (3～ 6个月 ,30 0～ 4 0 0g 只 )随机分为 2组 :(1)实验组 (n =16 )行双侧海绵体神经离断及左盆神经节移植入左侧阴茎脚内 ;(2 )对照组 (n =10 )仅离断双侧海绵体神经。1个月及 3个月后阿朴吗啡皮下注射检测勃起功能 ,电刺激左阴茎脚移植区域或右侧盆神经节比较海绵体内压的变化 ,NADPH染色检测海绵体内一氧化氮合酶 (NOS)阳性神经纤维 ,透射电镜观察盆神经节移植后的存活情况。结果　两组大鼠 1个月及 3个月后注射阿朴吗啡后均无勃起反应 ;电刺激左阴茎脚盆神经节移植区域后亦不能导致勃起。 1个月后电刺激两组左阴茎脚后的海绵体内压变化分别为 (9 4 1± 3 2 0 )、(4 16± 2 5 8)cmH2 O(t=4 76 9,P <0 0 5 ) ,3个月后分别为 (13 6 7± 4 18)、(5 0 9± 2 74 )cmH2 O(t=9 18,P <0 0 5 )。两组大鼠左阴茎脚区域的NOS阳性神经纤维数目 1个月后分别为 (2 18 7± 2 4 5 )、(18 0± 3 7) (t=14 77,P <0 0 5 ) ,3个月后分别为 (183 2± 19 7)、(19 0± 3 8) (t =12 18,P <0 0 5 ) ;透射电镜证实了神经节移植后的存活。结论　盆神经节海绵体内移植后可以存     

一氧化氮与雄激素在阴茎勃起中的作用

近年来研究表明 ,一氧化氮 ( NO)是介导阴茎勃起的一种神经递质〔1〕。最近又有实验表明 ,一氧化氮合酶 ( NOS)与雄激素有依赖关系〔2〕。可见 ,NO与雄激素在阴茎勃起中有明显作用。本文现对此作一综述。1　 NO在阴茎勃起中的作用在人体内 ,NO在 NOS的作用下 ,催化 L-精氨酸 (     

美蓝抑制侧脑室注射催产素诱发阴茎勃起的实验研究

为阐明阴茎勃起的中枢性机制 ,对 2 0例雄兔进行实验研究显示 :兔基础阴茎海绵体压 (2 .5± 1.8)mmHg ,经侧脑室内注射催产素 5 μg及 10 μg ,可诱发周期性有节律的阴茎海绵体内压升高 ,最高阴茎海绵体平均压分别为 (4 .5± 3.5 )mmHg及 (31± 10 )mmHg。海绵体注射美蓝可抑制催产素的中枢勃起效应 ,间接表明NO仍是阴茎勃起机制中的最重要的神经递质     

伊木萨克片对半去势雄性大鼠勃起功能的影响

目的 研究伊木萨克片对半去势雄性大鼠勃起功能的影响.方法 从60只性功能正常的雄性SD大鼠中随机取出10只为正常对照组,余50只行右侧睾丸摘除后随机分为半去势空白组、男宝对照组、伊木萨克低、中、高剂量组,经药物干预6周后行阿朴吗啡(Apomorphine,APO)勃起试验,镜检阴茎海绵体的形态改变,采用免疫组化SP法检测各组大鼠阴茎组织中nNOS、eNOS蛋白表达.结果 (1)半去势空白组勃起潜伏期显著长于正常对照组(P<0.01),伊木萨克低、中、高剂量组勃起潜伏期显著短于半去势空白组和男宝对照组(P<0.05),但长于正常对照组(P<0.05),伊木萨克片低、中、高剂量组之间差异则无统计学意义(P>0.05):(2)半去势空白组阴茎组织中eNOS、nNOS蛋白表达低于正常对照组(P<0.05).伊木萨克低、中、高剂量组大鼠阴茎组织中eNOS、nNOS蛋白表达均显著高于半去势空白组和男宝对照组(P<0.05),其中eNOS在伊术萨克片中剂量组显著高于正常对照组(P<0.01),而伊木萨克片低、高剂量组与正常对照组之间的差异则无统计学意义(均为P>0.05);nNOS在伊木萨克片低、中、高剂量组与正常对照组及伊木萨克片低、中、高剂量组之间差异无统计学意义(P>0.05).结论 (1)半去势可显著影响雄性大鼠的阴茎勃起功能;(2)伊木萨克片干预后能够显著增强半去势大鼠的阴茎勃起功能,其机制可能和增加阴茎组织中eNOS、nNOS蛋白表达有关.     

The efficacy, safety and tolerability of intracavernous PNU-83757 for the treatment of erectile dysfunction

PURPOSE: Despite the introduction of sildenafil citrate many men with erectile dysfunction remain dependent on intracavernous therapy. While the majority achieves satisfactory results with currently available intracavernous preparations, all preparations have undesirable side effects, including priapism, fibrosis and post-injection pain. We determined the efficacy, safety and tolerability of the erectogenic potassium channel opener PNU-83757. MATERIALS AND METHODS: We selected 66 men with erectile dysfunction of vascular etiology for intracavernous injection of PNU-83757 in a single dose, single blind, placebo controlled study. Of the 6 patients allocated into each of 11 dose groups 5 received active drug and 1 received placebo. Groups received progressive doses of PNU-83757 or placebo. Holter monitoring was performed at scheduled intervals. Heart rate, and systolic, diastolic and mean blood pressure were assessed at scheduled intervals. Blood samples were obtained for pharmacokinetic study. Patients were evaluated at regular intervals for adverse events. Investigators and patients evaluated efficacy. RESULTS: The first complete erection was observed at 10 mcg. Of the 25 patients receiving active drug in the 60 to 140 mcg. groups only 1 had no erectile response, 15 had partial erection and 9 had complete erection. No serious adverse events or cardiovascular effects were noted. CONCLUSIONS: The minimum effective dose for complete erection was 10 mcg. The erectile response reached a plateau between 60 and 140 mcg., suggesting minimal improvement in efficacy at higher doses. Patient evaluation of erectile quality corresponded well with that of investigators. PNU-83757 was efficacious and extremely well tolerated, and the only adverse events were mild. No cardiovascular side effects were observed at any dose. PNU-83757 intracavernous injections caused no post-injection pain in any patient, which may make PNU-83757 superior to alprostadil in a select group. Further study is required to evaluate the efficacy of PNU-83757 combined with other drugs and with sexual stimulation.     

The effects of androgen on penile reflex, erectile response to electrical stimulation and penile NOS activity in the rat

Aim: To investigate the effects of androgen on penile erection through the reflex arc and penile corpus cavernosum,and study the respective roles of testosterone (T) and dihydrotestosterone (DHT) in penile erection ira rats. Methods:Male Sprague-Dawley rats were castrated and implanted with silastic brand silicone tube containing T or DHT, with orwithout daily injections of a 5a-reductase inhibitor, MKM-434. The penile reflex, erectile response to electrical stimula-tion (ES) of the cavernous nerves and penile nitric-oxide synthase (NOS) activity were observed under varying andro-genic status. Results: Penile reflex erection in the rat was, on the whole, related to serum T levels though the numberof glans engorgernents was not. The number of cups and flips was significantly decreased by castration, and restoredto the control level by T supplementation. Erectile response to ES and NOS activity in penile tissue was also related toserum T level. T administered together with a ,5a-reductase inhibitor no longer restored the number of reflex erection,erectile responses to ES and NOS activity in the corpus cavemosum. Conclusion: Androgen influenced the penile re-flex arc, corpus cavemosum, and the perinea] striated muscles, ha reflex erection, erectile response to ES and penileNOS activity in the rat, T seeras to be first conyerted to DHT, the more active androgen modality. (Asian JAndrol1999Dec; 1: 169-174)     

大鼠阴茎组织中NOS表达及增龄的影响

为探讨大鼠阴茎组织中一氧化氮合酶分布及增龄对其的影响。本文采用ＮＡＤＰＨｄ组化对不同月龄大鼠阴茎组织进行染色。结果显示ＮＯＳ主要分布于大鼠阴茎组织平滑肌细胞,而内皮和社会纤维含量较少;随年龄增加,阴茎组织中ＮＯＳ表达逐渐减弱,各月龄组间差别明显。     

In vivo and in vitro investigation of the effects of sildenafil on rat cavernous smooth muscle

PURPOSE: We investigated the effect of sildenafil on rat erectile tissues in vivo and in vitro. MATERIALS AND METHODS: Intracavernous pressure was recorded in pentobarbital anesthetized, male Sprague-Dawley rats and we studied the effect of 100 or 200 microg/kg(-1) sildenafil given intravenously. In an isolated endothelin-1 contracted strip preparation of rat corpus cavernosum we also assessed the effect of sildenafil on the response to electrical field stimulation of the nerves. RESULTS: Electrical stimulation of the cavernous nerve induced a frequency dependent increase in intracavernous pressure of a mean plus or minus standard error of mean 55 +/- 3 mm Hg at 20 Hz, corresponding to a mean of 47% +/- 2% of mean arterial pressure. The 100 microg/kg(-1) dose did not increase intracavernous pressure but significantly increased mean decay time of the pressure response from 16 +/- 3 to 35 +/- 3 seconds (p <0.001). In vitro sildenafil significantly enhanced the amplitude and duration of the relaxation induced by the electrical stimulation of corpus cavernosum strips in a concentration dependent fashion. CONCLUSIONS: In anesthestized rats sildenafil significantly prolonged the decay period of the intracavernous pressure response induced by electrical stimulation of the cavernous nerve but it did not increase the amplitude. Sildenafil enhanced the amplitude and duration of the relaxant response to electrical field stimulation in isolated corpus cavernosum tissue.     

Effects of castration and testosterone replacement on veno-occlusion during penile erection in the rat

Aim: To determine if androgens directly regulate veno-occlusion or if androgens act indirectly to maintain the penilestructures which control outflow. Methods: Using CASTRATE and TESTO rats, measurement was made of meanarterial pressure (MAP), intracavernosal pressure (CCP), and intracavernosal flow (CCF) during erection resultingfrom stimulation of the autonomic innervation of the penis. CCP and CCF were also measured during saline infusioninto the cavernosal sinuses before and after treatment with sodium nitroprusside (SNP, a nitric oxide donor drag) tofully relax cavernosal smooth muscle. Penile tissue was also collected to measure the content of α actin and proline andhydroxyproline to determine if brief withdrawal of androgenic support led to changes in the number of smooth musclecells or the collagen content of the tissue. Results: Infusion of saline into the cavernosal sinuses demonstrated thatveno-occlusion was defective in CASTRATE rats while reno-occlusion was fully functional in TESTO animal     

Potentiation of reflex erectile responses in the anaesthetized rat by the selective melanocortin receptor 4 agonist MB243

OBJECTIVE

To assess the potentiation of erectile responses induced by electrical stimulation (ES) of the dorsal penile nerve (DPN) in the urethane‐anaesthetized rat by the selective melanocortin receptor 4 agonist MB243.

MATERIALS AND METHODS

Intracavernosal and blood pressures (ICP and BP, respectively) were monitored in urethane‐anaesthetized rats after complete spinal cord transection at the thoracic level. Erectile responses were induced by ES of the DPN (train of square wave pulses of 1 ms and 6 V for 20 s at 1, 2 and 5 Hz) after i.v. injection of either saline or MB243, 3 mg/kg, in two groups of six rats. The maximal and mean ICP, and the area under the curve (AUC) of the ICP response, corrected for the corresponding BP, were measured and used as an index of erectile function (ICPmax/BP, ICPmean/BP and AUC/BP, respectively).

RESULTS

MB243 increased the number of spontaneous erections between the injection and the first ES when compared with the vehicle group, but this difference was not statistically significant. ES of the DPN induced frequency‐dependent erectile responses, the mean (sem ) ICPmean/BP was 0.26 (0.02), 0.34 (0.04) and 0.39 (0.05) after administration of saline (vehicle) at 1, 2 and 5 Hz, respectively. All the variables, except the ICPmax/BP at 5 Hz, were significantly increased in the group injected with MB243 when compared with the vehicle group (P < 0.05 for ICPmax/BP and ICPmean/BP; P < 0.01 for AUC/BP). The AUC/BP showed the greatest increases of (+79%, +60% and +44% at 1, 2 and 5 Hz, respectively) in the group injected with MB243 compared with the vehicle group.

CONCLUSION

Erectile responses induced by ES of the DPN in spinalized, urethane‐anaesthetized rat are suitable for evaluating the proerectile facilitator activity of selective peripherally restricted melanocortin receptor 4 agonists. This model represents a valuable alternative to the classically used cavernous/pelvic nerve stimulated model.     

Nitric oxide synthase gene transfer for erectile dysfunction in a rat model

OBJECTIVE: To determine whether over-expression of nitric oxide synthase (NOS) in the corpus cavernosum of the penis improves erectile function, as NO is an important transmitter for genitourinary tract function, mediating smooth muscle relaxation and being essential for penile erection. MATERIALS AND METHODS: The inducible form of the enzyme NOS (iNOS) was introduced into the corpus cavernosum of adult Sprague-Dawley rats (250-300 g) by injecting a solution of plasmid, adenovirus or adenovirus-transduced myoblast cells (adeno-myoblasts). Plasmid, adenovirus and adeno-myoblasts encoding the expression of the beta-galactosidase reporter gene were also injected into rats. RESULTS: Throughout the corpora cavernosum there was expression of beta-galactosidase after injecting each of the three solutions. Maximum staining was greatest for adeno-myoblast, then adenovirus and then plasmid. The mean (sd) basal intracavernosal pressure (ICP) of iNOS-treated animals (adenovirus and adeno-myoblast) increased to 55 (23) cmH2O, compared with naive animals with a basal ICP of 5 (6) cmH2O (P = 0.001). Stimulating the cavernosal nerve (15 Hz, 1.5 ms, 10-40 V, 1 min) resulted in a doubling of the ICP (adenovirus and adeno-myoblast) from the basal level of the iNOS-treated animals. Direct in situ measurement of NO showed the release of 1-1.3 micro mol/L in the adeno-myoblast penis. CONCLUSION: Myoblast-mediated gene therapy was more successful for delivering iNOS into the corpus cavernosum than direct adenovirus injection or plasmid transfection. Surprisingly, implanting muscle cells into the penis is not only feasible but also beneficial. Gene therapy for NOS may open new avenues of treatment for erectile dysfunction. Control of NOS expression would be necessary to prevent priapism.     

淫羊藿次苷Ⅱ对大鼠阴茎海绵体压力、平均动脉血压的影响及其作用机制的研究

目的 淫羊藿次苷Ⅱ是淫羊藿中提取分离的单体,为了解淫羊藿次苷Ⅱ对阴茎性功能障碍(ED)的疗效,通过体内试验观察其对阴茎海绵体压力和平均动脉血压的影响及作用机制.方法 麻醉下游离大鼠左侧颈总动脉和左侧阴茎海绵体,允别插管与电生理仪连接;游离左侧海绵体神经(CN),采用电生理仪刺激器连接双极电极刺激;检测不同浓度的淫羊藿次苷Ⅱ在刺激CN后对阴茎海绵体压力(ICP)和平均动脉血压(MAP)影响,淫羊藿苷、西地那非、罂粟碱作为对照组.同时观察可溶性环鸟苷酸(sGC)抑制剂H-[1,2,4]噁二唑[4,3.A]喹喔啉(ODQ)、一氧化氮合酶(NOS)抑制剂N~ω硝基-L-精氨酸(LNNA)及一氧化氮生成抑制剂亚甲蓝(methylene blue,MB)对淫羊藿次苷Ⅱ(10~(-4)mol/L)诱发ICP/MAP变化的影响.结果 4组药物均剂量依赖性显著提高ICP(P<0.01),淫羊藿次苷Ⅱ、淫羊藿苷和西地那非对MAP无显著影响(P>0.05),而罂粟碱浓度达10~(-4)mol/L后,即可显著降低MAP(P<0.01).在受试浓度下,LNNA、MB和ODQ可显著抑制淫羊藿次苷Ⅱ诱发的ICP变化(P<0.01),对两地那非诱发的ICP变化无影响(P>0.05).结论 淫羊藿次苷Ⅱ和淫羊藿苷呈剂量依赖性地提高大鼠阴茎勃起功能(ICP),淫羊藿次苷Ⅱ效价强度为淫羊藿苷的2.44倍,对平均动脉血压没有显著影响,其机制可能与增强阴茎海绵体NO-cGMP通路的活性有关.     

Effect of exogenous l-arginine and ageing on NO and ET-1 in penile tissue of rat

The aim of this study was to investigate the effect and significance of l ‐arginine and ageing on nitric oxide (NO)‐cyclic guanosine monophosphate (cGMP) pathway and ET‐1 in penile tissue of rats. The different months old rats were divided into control group and experiment group randomly, the content of NO, cGMP, the changes of activity of Nitrous Oxide Systems (NOS) and the content of endothelin‐1(ET‐1) in penile tissue were determined. Along with ageing, NO and the activity of NOS in penile tissue increased at first and then decreased (P < 0.001). The content of cGMP reduced obviously (P < 0.001), the content of ET‐1 had a tendency to increase, and the ratio of ET‐1/NO increased significantly (P < 0.001 or P < 0.01). After feeding rats with l ‐arginine for some time, both the activity of NOS and the content of cGMP increased significantly in penile tissue (P < 0.001), while there was no obvious change in the content of ET‐1. Our study shows that whether the smooth muscle cells relax or contract might be decided by the content of cGMP and value of ET‐1/NO in penile tissue. l ‐arginine had significant effect on increasing the activity of NOS and the content of NO and cGMP, indicating that l ‐arginine has potential clinical value to be used in treating ED.