With the illustration of the L-Arg-NO-cGMP pathway in penile erection,the researches on nitric oxide synthases(NOSs),which produce nitric oxide(NO)as the main messenger to control the process,has stayed in the spotlight.nNOS locates in neuroal tissues and eNOS is binding on the membrane of cavernous sinus endothelium with caveolin.The nNOS & eNOS are expressed constitutively.The activation of nNOS & eNOS is more dependent on Ca2+ concentration than iNOS,which is seldom expressed except in aged or pathological conditions.It is now clear that nNOS may initiate cavernosal tissue relaxation under the regulation of PDZ zone when transcripted,while phosphorylated eNOS may facilitate attainment and maintenance of full erection.iNOS expression stimulated by the cytokines may be beneficial(cytoprotective or anti-fibrotic)or deleterious(cytotoxic)according to the tissue environment.Gene therapies based on NOSs have attained a great deal of achievements in animal experiments and will promise a wonderful future.
