Objective: To determine if nitric oxide synthase activity within the male reproductive tract is regulated by androgen.
Design: Nitric oxide synthase activity was measured in the reproductive organs of three groups of mature rats: unoperated controls, 1-week castrates, and 1-week castrates given T capsules at the time of surgery. The presence of nitric oxide synthase activity was confirmed by using the nitric oxide synthase-specific inhibitor N-nitro-L-arginine methyl ester (L-NAME).
Results: After castration, nitric oxide synthase activity was significantly reduced by 88%, 73%, and 54% in the caput, corpus, and cauda epididymidis, respectively. In the penis, nitric oxide synthase activity decreased 45% and nitric oxide synthase protein decreased 57% after castration. In the seminal vesicle and lateral prostate, nitric oxide synthase activity increased significantly after castration from nondetectable levels in controls. Nitric oxide synthase activity in the coagulating gland and ventral and dorsal prostate did not change after castration. The changes in nitric oxide synthase activity in all organs after castration were prevented by T replacement. Additionally, the activity measured in every organ in all three treatment groups was > 90% inhibited by L-NAME.
Conclusion: These data demonstrate that androgen differentially affects nitric oxide synthase activity in the male reproductive tract. To the best of our knowledge this is the first time that nitric oxide synthase activity has been shown to be influenced by androgen in any tissue.