INVESTIGATIVE UROLOGY

Improvement in relaxation response in corpus cavernosum from trained rats
Claudino MA, Priviero FBM, Teixeira CE, de Nucci G, Antunes E, Zanesco A
Department of Pharmacology, Faculty of Medical Sciences, UNICAMP, Campinas, São Paulo, and Department of Physical Education, Biosciences Institute, UNESP, Rio Claro, São Paulo, Brazil
Urology 2004; 63: 1004-1008.

• Objectives: To evaluate the contractile and relaxing responses in rat corpus cavernosum (RCC) from rats after 8 weeks of run training, because erectile function is highly dependent on nitric oxide (NO) from nitrergic fibers or endothelium. Physical activity enhances NO production and improves endothelial function, with beneficial effects on cardiovascular disease.
• Methods: The training program consisted of 8 weeks of run training, 5 days/wk, and each session lasted 60 minutes. The RCC was isolated, and concentration-response curves to NO, acetylcholine, sodium nitroprusside, phenylephrine, and endothelin were obtained. The excitatory and inhibitory effects of electrical field stimulation (2 to 32 Hz) were also evaluated.
• Results: NO (0.1 to 100 µM) and sodium nitroprusside (0.01 to 1000 µM) produced a relaxing effect in RCC in a dose-dependent manner, with the maximal responses to NO (control 62% ± 4%, trained 88% ± 3%) and sodium nitroprusside (control 83% ± 3%, trained 95% ± 2%) significantly enhanced after 8 weeks of run training. However, acetylcholine-induced relaxations were not affected by exercise. Similarly, electrical field stimulation-induced relaxations were significantly increased in RCC from trained rats at 2 Hz (control 2.4% ± 0.3%, trained 4.2% ± 0.5%) and 4 Hz (control 5.3% ± 1.2%, trained 12.5% ± 1.7%). The contractile sensitivity of RCC to phenylephrine (0.01 to 100 µM) and endothelin (0.01 to 100 nM) was not modified by training exercise.
• Conclusions: Our findings suggest that run training enhances functional responses in rat RCC that involves increases in the NO-cyclic guanosine monophosphate signaling pathway by endothelium-independent mechanisms that is not accompanied by changes in contractile sensitivity.
  
  
• Editorial Comment
  Previous studies have associated the beneficial effect of regular physical activity on cardiovascular diseases, with improvement in endothelium-derived relaxing factor production, reduction of sympathetic drive, and increases in parasympathetic activity to the peripheral tissues.
  The authors perform the present experience aiming to evaluate the functional responses to both vasodilating agents (sodium nitroprusside [SNP], acetylcholine [ACh], NO) and vasoconstricting agents (phenylephrine [PE] and endothelin-1 [ET-1]) in rat corpus cavernosum (RCC) after 8 weeks of treadmill training.
  The authors demonstrated objectively by the first time that physical training has beneficial effects on functional responses of RCC, because the run training program for 8 weeks increased the relaxation response to NO, SNP, and EFS.

Dr. Francisco J.B. Sampaio
Full-Professor and Chair, Urogenital Research Unit
State University of Rio de Janeiro
Rio de Janeiro, Brazil