Effect of androgen on neuronal nitric oxide synthase and endothelial nitric oxide synthase in corpus cavernosum of castrated rats

Objective To investigate the effect of different androgen levels on neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS) in corpus cavernosum of castrated rats.Methods Forty Sprague-Dawley male rats were randomly divided into sham operated group (n =10) and operated group (n =30).The rats in operated group were castrated and divided into 3 subgroups:subgroups 1 and 2 were treated with high dose (20 mg/kg) or low dose (10 mg/kg) testosterone undecanoate respectively each day,and subgroup group 3 was given normal saline.After 4 weeks of treatment,the rats in each group were sacrificed for detection of nNOS and eNOS by immunohistochemistry and Western blotting.Results nNOS and eNOS protein expression was detectable in the penis tissue of all rats.The nNOS and eNOS expressin levels in sham operated group were 98.24 ± 3.02 and 80.04 ± 2.96,92.81 ± 3.37 and 78.75 ±4.02 in subgroup 1,45.70 ±3.83 and 75.68 ±5.36 in subgroup 2,and 20.24 ±4.06 and 71.64 ± 3.04 in subgroup 3.The nNOS expression level in castrated groups was lower than in sham operated group and restored after testosterone supplement.There was no significant difference in the eNOS expression among the groups.Conclusion The expression of eNOS is androgen independent,and that of nNOS is androgen dependent.Androgen regulates penile relaxation of smooth muscle probably through nNOS pathway. Key words: Androgen;  Corpora cavernosa;  Neuronal nitric oxide synthase;  Endothelial nitric oxide synthase