L-arginine supplementation influenced nitrite but not nitrate and total nitrite in rabbit model of hypercholesterolemia. 
The assessment of altered nitric oxide (NO) availability is of potentially important diagnostic and prognostic significance.  The present study is aimed to investigate the effect of L-arginine (as a natural NO donor) supplementation on NO metabolite in a rabbit model of hypercholesterolemia to find a reliable marker for endothelial NO production.  White male rabbits (n = 30) randomly assigned to 2 groups.  Rabbits were fed 1% high-cholesterol diet (HC group, n = 15), or HC diet with oral L-arginine (3% in drinking water) (HC + L-arginine group, n = 15) for 4 weeks.  The serum levels of lipids, L-arginine, total NO metabolites (NOx), nitrite and nitrate were measured before and after the study.  In this study, L-arginine supplementation led to a significant increased plasma level of L-arginine.  The serum level of nitrite was significantly higher in L-arginine treated group while serum level of nitrate and NOx was significantly lower than HC group.  As the result of our study showed, nitrite is a useful marker of endogenous endothelial NO production and although frequently used, neither nitrate nor NOx are reliable markers of acute changes in endothelial NO synthase activity.