Effect of androgen deprivation on penile ultrastructure

Aim: To investigate the ultrastructural changes of penile corpus cavernosum and tunica albuginea in rats treated with castration or finasteride. Methods: Eighteen male Sprague-Dawley rats of nine weeks old were randomly divided into three groups with 6 rats each. Group A served as the control, Group B was castrated and Group C, treated with finasteride. Four weeks later, rats were anesthetized and blood samples obtained for the determination of serum testosterone (T) and dihydrotestosterone (DHT) levels; penile tissues were taken for scanning electron microscopy. Results: The T, free T and DHT levels in Group B and the DHT level in Group C were significantly lower than those in Group A (P<0.05). The tunica albuginea was significantly thinner in Group B than that in Group A (P<0.05), but there was no significant difference between Group C and Group A (P>0.05). Elastic fibers in the tunica albuginea of Group A were very rich and arranged regularly and undulatedly, but in Group B, most of the elastic fibers     

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)     

阴茎勃起神经递质CGRP蛋白表达的雄激素依赖性研究

目的 研究大鼠阴茎神经组织降钙素基因相关肽(CGRP)蛋白表达的雄激素依赖性。方法 64只雄性10周龄Sprague Dawley大鼠分为4组：A组为对照组，B组为去势组，C组为去势后肌注十一酸睾酮组，D组为喂饲保列治组。模型建立后分别在4周和10周处死部分大鼠，取腔静脉血和阴茎组织，应用放射免疫技术测定血睾酮(T)和二氢睾酮(DHT)浓度，应用免疫组化技术和计算机图象分析系统观察阴茎组织OGRP阳性神经纤维面积比例。结果 各实验组T和DHT含量低于对照组。4周时实验组和对照组阳性神经纤维面积比例的差异无统计学意义。10周时对照组阳性神经纤维面积比例明显高于实验组。各实验组4周模型和10周模型两两比较阳性神经纤维面积比例前者大于后者；对照组4周模型和10周模型阳性神经纤维面积比例无差异。结论 雄激素水平降低可引起大鼠阴茎神经组织CGRP蛋白表达下调，该影响有时间依从性。     

Pharmacological effects of the lipidosterolic extract of Serenoa repens (Permixon) on rat prostate hyperplasia induced by hyperprolactinemia: comparison with finasteride

BACKGROUND: The growth of the prostate gland is mainly dependent on androgens. Other hormones, like prolactin (PRL), also influence prostate development. Our purpose was to analyze and compare the effects of two drugs (5alpha-reductase inhibitor) used in the therapy of benign prostatic hyperplasia: lipidosterolic extract of Serenoa repens (LSESR), and finasteride in an in vivo model of rat prostate hyperplasia induced by hyperprolactinemia. METHODS: Hyperprolactinemia was induced by 30 daily injections of sulpiride. Wistar rats received daily gavages of LSESR or finasteride. We used the following groups: control, castrated, castrated with a substitute testosterone (T), or 5alpha-dihydrotestosterone (DHT) implant. RESULTS: Hyperprolactinemia increases the wet weight and induces hyperplasia in the lateral prostate (LP). Unlike finasteride, LSESR significantly reduced LP growth and hyperplasia in castrated, DHT-implanted, and sulpiride-treated rats. CONCLUSIONS: Finasteride was only capable of inhibiting the effect of androgens on rat prostate enlargement. LSESR inhibited not only the androgenic but also the trophic effect of PRL in rat LP hyperplasia.     

Preliminary study on androgen dependence of calcitonin gene-related peptide in rat penis

To study the androgen dependence of the neurotransmitter, calcitonin gene-related peptide (CGRP) in rat penis. METHODS: Forty-four Sprague-Dawley rats were randomly divided into Group A (intact controls), Group B (castrated) and Group C (gavaged with finasteride 4.5 mg.kg(-1).day(-1)). Four and ten weeks later respectively, half of rats in each group were anaesthetized. Blood samples were taken for the measurement of serum testosterone and dihydrotestosterone (DHT) by means of radioimmunoassay. Penile samples were harvested for the investigation of calcitonin gene related peptide (CGRP)-immunoreactive nerve fibers with immunohistochemistry. The computer-assisted imaging analysis system was applied to calculate the area proportion of the CGRP-positive nerve fibers (CGRP-PNF) in each group. RESULTS: 1) Both 4 and 10 weeks later, testosterone and DHT levels in Group B decreased significantly compared with those in Group A, (P <0.05, P <0.01, respectively); DHT level in Group C was also significantly decreased in comparison with that in Group A for both 4- and 10- week animals (P <0.05); 2) There was no significant differences in area proportion of CGRP-PNF among Groups A, B and C 4 weeks after treatments (P >0.05); However, 10 weeks later, the proportion of CGRP-PNF in Groups B and C was significantly less than that in Group A (P <0.01); 3) The proportion of CGRP-PNF of 4-week animals in Groups B and C was significantly higher than that of 10-week animals (P <0.05). CONCLUSION: The expression of neurotransmitter, CGRP may depend on androgens, including testosterone and DHT in rat penis.     

The antigonadotropic action of testosterone but not 7alpha-methyl-19-nortestosterone is attenuated through the 5alpha-reductase pathway in the castrated male rat pituitary gland

The enzyme 5alpha-reductase plays a significant role in the prostate to amplify the action of testosterone (T) by converting it to a more potent androgen, dihydrotestosterone (DHT). The role of 5alpha-reductase in the testosterone feedback inhibition of gonadotropin secretion from the pituitary has not been elucidated. Therefore, we investigated the role of 5alpha-reductase on T action in in vitro and in vivo models. Castration has been reported to increase the 5alpha-reductase activity in pituitary glands. Hence, the effect of castration duration on the conversion of T to DHT by pituitary homogenates and the responsiveness of pituitary monolayer cell cultures to gonadotropin-releasing hormone (GnRH) challenge exposure were investigated. Incubation of [3H]-T with pituitary homogenates showed that the conversion of T to 5alpha-reduced metabolites was two- to threefold greater in pituitaries from rats who had been castrated for 14 days compared with those castrated for 1 day. In addition, the GnRH-stimulated release of LH from monolayer cell cultures of pituitaries from rats castrated for 1 day was twofold greater, whereas that from rats castrated for 2 weeks was six- to sevenfold greater compared with basal luteinizing hormone (LH) release. Hence we used rats castrated for 2 weeks to elucidate the role of 5alpha-reductase in T feedback inhibition. The inhibitory effects of the androgens T, 19-nortestosterone (19-NT), and 7alpha-methyl-19-nortestosterone (MENT) at 3 different concentrations (10(-9), 10(-7), and 10(-5) mol/L) on GnRH-stimulated LH release from monolayer cell cultures of pituitaries from rats castrated for 2 weeks were examined. All 3 androgens showed dose-dependent inhibition of LH release. MENT showed the greatest inhibition, followed by 19-NT and T. In the presence of finasteride (a 5alpha-reductase inhibitor), the inhibition of LH released by T and 19-NT were significantly greater. The inhibitory effect of MENT, which does not undergo 5alpha-reduction, was not altered by finasteride. In an in vivo study, rats castrated for 2 weeks received T with or without finasteride. There was a significantly greater suppression of serum LH in rats receiving T plus finasteride compared with those receiving T alone. These results suggested that 5alpha-reductase in the pituitary is not obligatory for the inhibitory action of T on gonadotropin secretion in the castrated rat. The action of MENT, a nonreducible androgen, on the pituitary is not affected by 5alpha-reductase.     

血红素氧合酶2在去势大鼠阴茎海绵体内的表达

目的:研究去势大鼠阴茎海绵体血红素氧合酶2(HO-2)和内皮型一氧化氮合酶(eNOS)的表达,探讨雄激素与HO-2、eNOS在ED中的作用及相关性。方法:10周龄雄性SD大鼠40只,分为4、8、12周组和正常对照组各10只,实验组采取手术切除双侧睾丸,对照组采取假手术。分别于术后4、8、12周测定大鼠血清睾酮(T)、阴茎海绵体内压(ICP)、平均颈动脉压(MAP),取阴茎标本,采用Western印迹分析阴茎海绵体HO-2含量,免疫组化分析HO-2和eNOS的表达。结果:去势各组血清T水平较正常对照组显著下降(P<0.05)。经3V、5V电压刺激后去势各组ICP/MAP值明显下降(P<0.05)。HO-2在正常和去势大鼠阴茎海绵体组织均有表达,去势4周组HO-2光密度分布曲线下面积(341.50±99.70)较正常组(876±443.36)和去势8周组(705.00±152.74)明显下降(P<0.05),去势8周与正常组之间无显著变化(P>0.05),去势12周没有检测到HO-2的表达。eNOS主要表达于阴茎海绵体血管内皮细胞,去势组eNOS(123.94±30.23)较正常组(421.21±125.12)差异有显著性(P<0.05)。T与eNOS和HO-2表达呈高度正相关(r=0.976、0.946,P均<0.05)。结论:雄激素可能通过影响大鼠阴茎海绵体HO-2、eNOS的表达参与阴茎勃起功能调控。     

血红素氧合酶在去势大鼠阴茎海绵体的表达

目的:研究血红素氧合酶(HO)在去势大鼠阴茎海绵体的表达,探讨其在雄激素缺乏的勃起功能障碍发生中的机制。方法:40只10周龄雄性SD大鼠随机分成:假手术2周组(A组),假手术4周组(B组),去势2周组(C组),去势4周组(D组)。术后2、4周检测血清睾酮水平,免疫组化及RT-PCR技术检测HO及nNOS在大鼠阴茎海绵体的表达。结果:去势组大鼠较假手术组血清睾酮水平显著下降,[AvsC:(283.222±117.171)ng/dlvs(7.117±3.700)ng/dl;BvsD:(289.280±87.413)ng/dlvs(48.826±19.477)ng/dl](P<0.01)、HO-1、HO-2蛋白表达明显降低(P<0.01),去势组HO-1、HO-2及nNOSmRNA表达较假手术组显著降低(P<0.01)。结论:雄激素可能通过HO-CO系统部分调控阴茎勃起功能。     

Vasoactive intestinal polypeptide, an erectile neurotransmitter, improves erectile function more significantly in castrated rats than in normal rats

What’s known on the subject? and What does the study add? Vasoactive intestinal polypeptide (VIP) is an important erectile neurotransmitter, and our previous study found that the mRNA expression of VIP was independent of androgens. The present study further investigated the vivo effect of VIP on erection. We found that not only the expression of VIP was independent of androgens, but also the effect of VIP on erection was independent of androgens. In fact, we found that VIP played a more significant role on erection in castrated rats than in normal rats.

OBJECTIVE

• ? To investigate the regulatory role of androgen in VIP‐mediated erectile effect. Androgen is essential for physiological erection. Vasoactive intestinal polypeptide (VIP) is an important erectile neurotransmitter. While previous studies demonstrated that VIP expression in the penis was androgen‐independent, it remains controversial whether androgen has any effect on VIP‐mediated erection.

MATERIALS AND METHODS

• ? Male SD rats were divided into a control group, a castration group, and a castration‐with‐testosterone‐replacement group. Four weeks later, each group was subdivided into low and high‐dose VIP subgroups and subjected to intracavernous injection of 0.5 and 2 µg VIP, respectively.
• ? Erectile function was tested by recording intracavernosal pressure (ICP) and mean arterial blood pressure (MAP) before and after VIP injection.
• ? The expressions of the VIP‐receptor (VPAC2), G‐protein stimulatory and inhibitory alpha subunits (Gs‐α, Gi‐α), and PDE3A in rat corpus cavernosum (CC) was qualified by real‐time PCR and Western blot analysis.

RESULTS

• ? Castration reduced erectile function while testosterone restored it. VIP improved erectile function in a dose‐dependent manner.
• ? High‐dose VIP significantly enhanced erectile function in castrated rats and there was no difference of ICP/MAP among three groups after injection of high‐dose VIP.
• ? Low‐dose VIP also resulted in a higher improvement of erectile function in castrated rats, although the ICP/MAP was lower in these rats than in the other two groups. VPAC2 and Gs‐α were up‐regulated while Gi‐α and PDE3A were down‐regulated in CC of castrated rats.

CONCLUSION

• ? VIP improves erectile function much more significantly in hypogonadal condition, mainly due to the higher expression of VPAC2, Gs‐α, and lower expression of Gi‐α and PDE3A in CC of castrated rats. Androgen may negatively regulate the erectile effect of VIP.

     

去势对大鼠阴茎海绵体功能和结构的影响

目的 :探讨雄激素对阴茎海绵体功能和结构的影响。　方法 :30只成年雄性大白鼠随机分为 3组 :阉割组、替代组及假手术对照组。于 1周后取阴茎海绵体 ,用紫外分光光度计测定其一氧化氮合酶 (NOS)活性 ,同时用ISEL法检测其细胞凋亡情况。　结果 :阉割组海绵体NOS活性下降 70 %并出现细胞凋亡 (P <0 .0 1) ,睾酮替代能阻止NOS活性降低及凋亡的发生 (P >0 .0 5 )。　结论 :雄激素可通过调节NOS活性及细胞的增殖与凋亡而维持阴茎海绵体的结构与功能。     

雄激素对大鼠腹叶前列腺GDNF mRNA表达的影响

目的 :探讨雄激素对大鼠腹叶前列腺中胶质细胞源性神经营养因子 (GDNF)mRNA表达的影响。　方法 :2 4只SD大鼠分为 3组 ,其中A组 (n =8)为假手术对照组 ,B组 (n =8)为去势组 ,C组 (n =8)为雄激素替代组 (去势后肌注十一酸睾酮 5 0mg/kg) ;术后 3d处死 ,通过半定量RT PCR检测GDNFmRNA在去势前后和雄激素替代组大鼠腹叶前列腺中的表达变化。　结果 :去势后大鼠前列腺的体积萎缩变小 ;雄激素替代组出现前列腺增生变大 ;对照组正常的大鼠前列腺有GDNFmRNA表达 ,去势组GDNFmRNA表达量减少 ,雄激素替代组GDNFmRNA表达量增加。与正常对照组比较 ,去势组的GDNFmRNA表达量显著减少 (P <0 .0 5 ) ,雄激素替代组的GDNFmRNA表达量显著增加(P <0 .0 5 )。　结论 :雄激素可增加GDNFmRNA表达 ,促进前列腺细胞生长。     

Effect of low androgen status on the expression of adenosine A2A and A2B receptors in rat penile corpus cavernosum

To investigate whether low androgen status affects erectile function by regulating the expression of adenosine A_2A and A_2B receptors in rat penile corpus cavernosum. Thirty‐six 8‐week‐old male Sprague‐Dawley rats were randomly divided into six groups: sham‐operated group (4w‐sham, 8w‐sham), castration group (4w‐cast, 8w‐cast) and androgen replacement group (4w‐cast+T, 8w‐cast+T). The rats in the androgen replacement groups were subcutaneously injected with testosterone propionate (3 mg/kg) every other day after castration. The maximum intracavernous pressure/mean arterial pressure (ICPmax/MAP), the expression of A_2A, A_2B, AKT and eNOS and the concentrations of cAMP and cGMP in the corpus cavernosum were detected at the 4th and 8th weeks after the operation. The serum testosterone level and the ratio of ICPmax/MAP decreased significantly in the castration group as compared to other groups (p < 0.01). There was no significant difference in the expression of A_2A receptor among groups, while the expression of A_2B, AKT and eNOS and the concentrations of cAMP and cGMP in the castration group were significantly lower than in other groups (p < 0.01). Low androgen status inhibits the AKT/eNOS/cGMP signalling pathways and the production of cAMP in the corpus cavernosum of castrated rats by down‐regulating the expression of A_2B receptor, and results in decreased of ICPmax/MAP.     

血管活性肠多肽基因转导增强阴茎勃起功能

目的 探讨阴茎海绵体勃起神经递质血管活性肠多肽(VIP)基因转导入糖尿病大鼠阴茎海绵体并表达多量VIP以增强勃起功能的可行性.方法 将构建的重组质粒pcDNA3/VIPcDNA注射入链尿佐菌素诱导的糖尿病大鼠阴茎海绵体,在注射3 d后测定阴茎海绵体内压(ICP),分别以正常空白、空白、单纯注射缓冲液和单纯注射pcDNA3载体对照.Dot blot法测定阴茎组织中VIP mRNA表达水平.结果 糖尿病大鼠阴茎海绵体注射重组质粒后3 d,电刺激海绵体神经,ICP较对照组明显升高(P＜0.05);阴茎组织VIP mRNA表达增多(P＜0.05).结论 成功将重组质粒pcDNA3/VIP cDNA转导入糖尿病阴茎海绵体,VIP mRNA表达增加能增强糖尿病大鼠阴茎海绵体的勃起功能.     

安雄对去势大鼠离体阴茎海绵体平滑肌舒张性的影响

目的 :探讨口服雄激素类药安雄对大鼠阴茎海绵体平滑肌舒张性的调节作用。　方法 :去势大鼠分别给予高、低剂量的安雄 ,与假手术组、去势组大鼠进行对照观察。治疗 4周后分别切取其阴茎海绵体 ,制成海绵体肌条 ,应用去甲肾上腺素对海绵体肌条进行预收缩 ,继予硝普钠 (SNP)、电刺激 (EFS)观测海绵体平滑肌的舒张性 ,比较各组的舒张百分率。　结果 :高剂量安雄 (2 0mg/kg)组其离体平滑肌条 ,对 10 -3 mol/LSNP和EFS的舒张百分率高于去势组 ;低剂量组 (10mg/kg)对 10 -3 mol/LSNP诱导的舒张百分率也高于去势组。统计学处理差异有显著性 (P <0 .0 1) ,　结论 :去势大鼠应用安雄可提高离体大鼠海绵体平滑肌的舒张百分率 ,可增强其海绵体平滑肌的舒张性     

缺氧诱导因子-1α在去势前后大鼠腹叶前列腺中表达的变化

目的探讨与缺氧相关的缺氧诱导因子-1α(HIF-1α)是否参与去势后前列腺萎缩过程.方法24只SD大鼠分为3组,其中A组(n=8)为假手术对照组,B组(n=8)为去势组,C组(n=8)为雄激素替代组(去势后肌注十一酸睾酮50mg/kg);术后3天处死,通过半定量RT-PCR检测与HIF-1α在去势前后前列腺表达变化.结果去势后大鼠前列腺的体积萎缩变小;雄激素替代组出现前列腺增生变大;对照组正常的大鼠前列腺有HIF-1 α mRNA低水平表达,去势组HIF-1α mRNA表达量增加,雄激素替代组HIF-1αmRNA表达量减少,与正常对照组比较,去势组的HIF-1α mRNA的表达量显著增加(P＜0.05),雄激素替代组的HIF-1αmRNA的表达量显著减少(P＜0.01).结论前列腺组织的缺氧参与去势后大鼠前列腺的早期萎缩过程.     

Effect of castration on penile erection in the dog

The reduction in sexual activity in hypogonadal men is at least partially due to a decrease in sexual interest, but it may also involve peripheral mechanisms. In the present experiments, the effects of castration on penile erection in dogs was investigated. The pressure within the corpus cavernosum was measured in intact anaesthetized dogs and in dogs castrated 2 weeks or more than 6 months previously. It was found that there was no significant difference between intact and castrated dogs in the magnitude or time course of increase in corpus cavernosal pressure induced by pelvic nerve stimulation or in the inhibitory effects of simultaneous stimulation of the sympathetic chain. Furthermore, the mean ED₅₀ value for contraction to phenylephrine of isolated strips of erectile tissue from the corpus cavernosum was not significantly different between groups. This suggests that the mechanism of penile erection is not affected by reducing the levels of testosterone.     

衰老对大鼠阴茎勃起机制的影响

为探讨衰老对阴茎勃起机制的影响程度,以不同月龄的雄性大鼠分别观察海绵体神经诱导的阴茎勃起,海绵体平滑肌的舒张功能以及阴茎含ＮＯＳ神经和平滑肌量。结果表明电刺激老年鼠海绵体神经可取得与年轻和中年鼠相当的勃起压力,但勃起潜伏期较长。注射罂粟碱提示老年海绵体平滑肌顺应性较年轻鼠差。检查还提示老年鼠阴茎内含ＮＯＳ神经和平滑肌纤维量有一定减少。实验证实衰老对阴茎勃起机制中关键性的组织结果和功能有一定影响,但     

Evidence for the regulation of prostatic oxytocin by gonadal steroids in the rat

Oxytocin and its receptor are present in the mammalian prostate, and the peptide has been shown to increase prostatic growth, 5alpha-reductase activity, and contractility. This study was performed to investigate whether local concentrations of the peptide were regulated by gonadal steroids in order to establish whether oxytocin has a physiological role in the prostate. Both intact and castrated adult Wistar rats were treated daily for 7 days with either testosterone propionate or the antiandrogen cyproterone acetate. Animals were then killed, and plasma hormone and prostatic oxytocin concentrations were measured. A separate group of rats was treated with the 5alpha-reductase inhibitor finasteride to investigate whether testosterone or dihydrotestosterone (DHT) was involved in regulating oxytocin concentrations. In a further series of experiments, rats were treated with diethylstilbestrol (DES) or the antiestrogen tamoxifen. Treatment with testosterone significantly decreased prostatic oxytocin, whereas reduction of androgens by castration or by administration of cyproterone acetate increased prostatic peptide concentrations without altering circulating levels of the peptide. Treatment with finasteride increased plasma testosterone but decreased DHT concentrations. Prostatic oxytocin concentrations were higher in finasteride-treated animals than in control animals with comparable testosterone levels. The data suggest that both testosterone and DHT are capable of decreasing prostatic oxytocin concentrations. Treatment with DES did not significantly alter prostatic oxytocin, but administration of tamoxifen decreased concentrations of the peptide, suggesting that low levels of estrogen may be necessary for oxytocin production. These data provide evidence that oxytocin is regulated by androgens, and we hypothesize that this regulatory mechanism may be involved in controlling prostatic growth.