Putative Asymmetric Dimethyl Arginine-Dimethylarginine Dimethylaminohydrolase Pathway in Rat Penile Tissue: A Biochemical and Functional Study

Shin, Jae Wook; Park, Kwanjin; Kim, Soo Woong; Paick, Jae Seung

Abstract

PURPOSE
Asymmetrical NG,NG-dimethyl-L-arginine (ADMA) is an endogenous inhibitor of nitric oxide synthase (NOS) and is metabolized by NG,NG-dimethylarginine dimethylaminohydrolase (DDAH). Although the ADMA-DDAH axis is widely distributed in human as well as rat tissues, the existence and the pathophysiologic role of DDAH in erectile function has not yet been studied. Therefore, we sought to demonstrate the presence of DDAH and investigate the relative amounts of two types of DDAH in rat cavernosal tissue. Also, we studied the effect of DDAH inhibition on erectile function in rats.
MATERIALS AND METHODS
We developed cDNA probes for rat DDAH 1 and 2 by specific reverse-transcriptase mediated polymerase chain reaction (PCR). The presence and relative distribution of both types of DDAH gene expression were assessed using real time PCR and immunoblotting. To inhibit cavernosal DDAH, a specific inhibitor of DDAH (S-2-amino-4(3-methylguadino)butanoic acid) was administered to anesthesized rats via intracavernosal injection. The corporal level of ADMA was measured by high performance liquid chromatography. Erectile function was assessed by comparing the results of cavernous electrostimulation before and 30 minutes after drug administration.
RESULTS
The presence of DDAH is demonstrated by the results of real time PCR and immunoblotting. Although both types were identified in rat penile tissue, type 2 was dominant. Intracavernosal injection of DDAH inhibitor markedly elevated the level of ADMA (0.86 nmol/g wet wt pretreatment to 4.25 nmol/g wet wt post-treatment) and resulted in a significant decrease of ICP/MAP in the anesthesized rats during cavernous electrostimulation.
CONCLUSIONS
Our study is the first to demonstrate the existence of the ADMA-DDAH axis in the rat penile tissue. Since inhibition of DDAH impeded erectile function, alteration of this axis may be another cause of erectile dysfunction.