BACKGROUND:
Antioxidants play an important role in scavenging of free radicals and protection against degenerative diseases. Previous studies have reported high antioxidant activity in some amino acids. In this study, the effect of L- Arginine (L-Arg) on serum lipid levels and serum lipid peroxidation were investigated in hypercholesterolemic rabbits.

METHODS:
A number of 15 rabbits (0.5-1.5 kg) were randomly divided into three groups (n=5) fed high-cholesterol diet (hypercholesterolemic control group), high-cholesterol diet + L-Arg (treatment group), and normal diet (normal control) for twelve weeks and then blood samples were obtained at the end of the experiment to analysis of serum total cholesterol (TC), triglyceride (TG), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), antioxidant capacity (AC), malondialdehyde (MDA), and conjugated diens (CDS). Antioxidant effects of L-Arg were investigated by use of erythrocyte and hepatocyte systems.

FINDINGS:
Significant differences were found in serum levels of TC, TG, LDL, AC, MDA, and CDs between L-Arg treatment group and hypercholesterolemic control group. HDL level in treatment group showed no significant difference in comparison to hypercholesterolemic control group. The results of In vitro studies also showed increasing L-Arg antioxidant effects with increasing its concentration and the most antioxidant capacity was seen in 250 µmol/L. This finding confirms the observed antioxidant effects of L-Arg in animal studies.

CONCLUSION:
The findings indicate that L-Arg has reduced effect on serum lipid levels and antioxidant activity in hypercholesterolemic rabbits.

KEY WORDS:
Hypercholesterolemia, antioxidant activity, lipid peroxidation, L-Arginine