Effect of exogenous l-arginine and ageing on NO and ET-1 in penile tissue of rat

The aim of this study was to investigate the effect and significance of l ‐arginine and ageing on nitric oxide (NO)‐cyclic guanosine monophosphate (cGMP) pathway and ET‐1 in penile tissue of rats. The different months old rats were divided into control group and experiment group randomly, the content of NO, cGMP, the changes of activity of Nitrous Oxide Systems (NOS) and the content of endothelin‐1(ET‐1) in penile tissue were determined. Along with ageing, NO and the activity of NOS in penile tissue increased at first and then decreased (P < 0.001). The content of cGMP reduced obviously (P < 0.001), the content of ET‐1 had a tendency to increase, and the ratio of ET‐1/NO increased significantly (P < 0.001 or P < 0.01). After feeding rats with l ‐arginine for some time, both the activity of NOS and the content of cGMP increased significantly in penile tissue (P < 0.001), while there was no obvious change in the content of ET‐1. Our study shows that whether the smooth muscle cells relax or contract might be decided by the content of cGMP and value of ET‐1/NO in penile tissue. l ‐arginine had significant effect on increasing the activity of NOS and the content of NO and cGMP, indicating that l ‐arginine has potential clinical value to be used in treating ED.