Increased serum arginase activity in depressed patients.

1. Arginase, an important part of the arginine-regulating system modulates nitric oxide generation; a neuroregulatory agent, which has been implicated in various neuropathological conditions. 2. In this regard, the authors investigated the arginine-nitric oxide pathway by measuring serum arginase activity in drug free major (n=18) and minor depressed outpatients (n=12) and healthy control subjects (n=30) in order to make a contribution to the understanding of disease mechanism. 3. Major depressed patients were found to have significantly higher serum arginase activity compared to controls (p<0.001) and minor depressives (p=0.001). Moreover, there was significant positive correlation between arginase activity and severity of depression in patients (p<0.001). 4. Results suggest that the arginine-nitric oxide pathway is involved in depression. Enhanced arginase activity in major depressed patients possibly leading to a decrease in nitric oxide synthesis may contribute to the symptomatology of depression.