Haas C A, Seftel A D, Razmjouei K, Ganz M B, Hampel N, Ferguson K
Department of Urology, Cleveland Veterans Affairs Medical Center, Case Western Reserve University, University Hospitals of Cleveland, Ohio 44106-5046, USA.
Urology. 1998 Mar;51(3):516-22. doi: 10.1016/s0090-4295(97)00715-2.
To evaluate whether alterations in nitric oxide (NO) synthesis or activity contribute to age-related erectile dysfunction and to elucidate the mechanisms causing these alterations using the rabbit as our model of aging.
We compared the ability of the rabbit cavernosal smooth muscle to relax in the organ bath in response to acetylcholine (Ach, endothelium-dependent vasodilator), sodium nitroprusside (SNP, an NO donor), and A23187 (a calcium ionophore) in young (6 month old) and aged (2.5 to 3.5 year old) rabbits. In addition, the immunohistochemical expression of endothelial nitric oxide synthase (eNOS) in both young and aged rabbit cavernosal tissue was examined. Endothelial integrity was examined immunohistochemically with JC70.
Ach-mediated relaxation of penile corporal tissue was significantly attenuated from a maximum of 68.39 +/- 6.27 (0.1 mM Ach, n = 4) in young rabbits to 39.02 +/- 4.88 (0.1 mM Ach, n = 6) in aged rabbits (P < 0.04). No statistically significant difference (P > 0.05) was noted between cavernosal relaxation to sodium nitroprusside between young rabbits (97.8%, 0.1 mM SNP, n = 5) and aged rabbits (76.1%, 0.1 mM SNP, n = 5). This suggested that the defect in the Ach-NO pathway was at the level of NO synthesis, not activity. Immunohistochemical staining for eNOS demonstrated upregulation in both the vascular endothelium and corporal smooth muscle of aged rabbit tissue compared with young rabbit cavernosal tissue (n = 5). Anatomic endothelial integrity was demonstrated in the young and aged rabbits by the presence of JC70. This suggested that the defect in the Ach-NO synthetic pathway was not at the level of eNOS and was not due to anatomic endothelial cell disruption. Finally, Ach-mediated cavernosal smooth muscle relaxation in the young rabbit was not significantly augmented (P > 0.05) in the presence of the calcium ionophore A23187 (10 microM). A23187, however, significantly augmented (P < 0.04) Ach-mediated relaxation in the aged rabbit from a maximum of 33.93 +/- 6.58 to 41.55 +/- 6.58 (10 microM Ach, n = 5). This suggested that a potential defect in the Ach-NO synthetic pathway was at the level of intracellular calcium flux and possibly at the level of the calcium-eNOS interaction.
Endothelium-dependent relaxation is attenuated in the aging rabbit; eNOS is upregulated in the aging rabbit; and no difference is noted in response to direct NO donation between the young and aged rabbit. The endothelium is anatomically intact in both the young and aging rabbit. The calcium ionophore A23187 augmented the attenuated vasorelaxation in the aging rabbit cavernosum (although not to the levels seen in the young rabbit cavernosum) and had no effect on the young rabbit cavernosum. These data suggest that erectile dysfunction in the aging rabbit cavernosum appears to be related to endothelial dysfunction and is characterized by eNOS upregulation and aberrant intracellular calcium fluxes.
以兔作为衰老模型，评估一氧化氮（NO）合成或活性的改变是否导致与年龄相关的勃起功能障碍，并阐明引起这些改变的机制。
我们比较了年轻（6月龄）和老年（2.5至3.5岁）兔海绵体平滑肌在器官浴中对乙酰胆碱（Ach，内皮依赖性血管舒张剂）、硝普钠（SNP，一种NO供体）和A23187（一种钙离子载体）的舒张能力。此外，检测了年轻和老年兔海绵体组织中内皮型一氧化氮合酶（eNOS）的免疫组化表达。用JC70免疫组化检测内皮完整性。
Ach介导的阴茎海绵体组织舒张从年轻兔的最大舒张68.39±6.27（0.1 mM Ach，n = 4）显著减弱至老年兔的39.02±4.88（0.1 mM Ach，n = 6）（P < 0.04）。年轻兔（97.8%，0.1 mM SNP，n = 5）和老年兔（76.1%，0.1 mM SNP，n = 5）对硝普钠的海绵体舒张之间未观察到统计学显著差异（P > 0.05）。这表明Ach-NO途径的缺陷在于NO合成水平，而非活性水平。与年轻兔海绵体组织（n = 5）相比，老年兔组织的血管内皮和海绵体平滑肌中eNOS的免疫组化染色显示上调。年轻和老年兔中JC70的存在证明了解剖学内皮完整性。这表明Ach-NO合成途径的缺陷不在于eNOS水平，也不是由于解剖学内皮细胞破坏。最后，在存在钙离子载体A23187（10 μM）的情况下，年轻兔中Ach介导的海绵体平滑肌舒张未显著增强（P > 0.05）。然而，A23187使老年兔中Ach介导的舒张从最大舒张33.93±6.58显著增强至41.55±6.58（10 μM Ach，n = 5）（P < 0.04）。这表明Ach-NO合成途径中的潜在缺陷在于细胞内钙通量水平，可能还在于钙-eNOS相互作用水平。
衰老兔中内皮依赖性舒张减弱；衰老兔中eNOS上调；年轻和老年兔对直接给予NO的反应未观察到差异。年轻和衰老兔的内皮在解剖学上均完整。钙离子载体A23187增强了衰老兔海绵体中减弱的血管舒张（尽管未达到年轻兔海绵体中的水平），且对年轻兔海绵体无影响。这些数据表明，衰老兔海绵体中的勃起功能障碍似乎与内皮功能障碍有关，其特征为eNOS上调和异常的细胞内钙通量。
