Enzyme activities of the nitric oxide-cGMP pathway in corpus cavernosum isolated from middle-aged rats

Eur J Pharmacol. 2003 Jul 18;473(1):65-70. doi: 10.1016/s0014-2999(03)01947-2.


Cyclic guanosine-3',5'-monophosphate (cGMP)-mediated mechanisms play an important role in vasodilation and blood pressure regulation. We investigated basal activity of the nitric oxide (NO)-cGMP signal transduction pathway in corpus cavernosum from both middle-aged and young rats, and the electrical field stimulation-induced relaxation in the organ was also evaluated. In middle-aged rats, nitric oxide synthase (NOS) and cGMP-phosphodiesterase activities were significantly decreased; however, guanylate cyclase activity was similar. cGMP concentration, a secondary messenger of NO, remained almost the same level as compared with young rats. These results suggest that decrease in cGMP-phosphodiesterase activity is likely to account for the maintenance of cGMP concentration. In isolated corpus cavernosum from middle-aged rats, electrical field stimulation-induced relaxation was partially impaired. These results suggest that downregulation of the NOS and cGMP-phosphodiesterase activities are early events in the pathogenesis of erectile dysfunction.

Publication types

  • Comparative Study

MeSH terms

  • Adrenergic Agents / pharmacology
  • Age Factors
  • Animals
  • Cyclic GMP / metabolism*
  • Electric Stimulation
  • Enzyme Inhibitors / pharmacology
  • Guanylate Cyclase / metabolism
  • In Vitro Techniques
  • Isometric Contraction / drug effects
  • Isometric Contraction / physiology
  • Male
  • Muscle, Smooth / drug effects
  • Muscle, Smooth / enzymology
  • Nitric Oxide / metabolism*
  • Nitric Oxide Synthase / metabolism
  • Penis / drug effects*
  • Penis / enzymology*
  • Phosphoric Diester Hydrolases / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Cytoplasmic and Nuclear / metabolism
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • Soluble Guanylyl Cyclase


  • Adrenergic Agents
  • Enzyme Inhibitors
  • Receptors, Cytoplasmic and Nuclear
  • Nitric Oxide
  • Nitric Oxide Synthase
  • Phosphoric Diester Hydrolases
  • Guanylate Cyclase
  • Soluble Guanylyl Cyclase
  • Cyclic GMP