Effect of dietary arginine on urinary nitrate excretion in germ-free rats

The effect of dietary arginine on the endogenous synthesis of nitrate in germ-free rats was investigated. The animals were fed, for up to 18 days, purified diets containing either casein or lactalbumin (proteins differing in arginine content) with or without additional free arginine. Urine was collected from all animals for 4 days, and the animals were then dosed ip with Escherichia coli lipopolysaccharide (LPS) to stimulate nitrate synthesis and urine collected for a further 4 days. The urine samples were analysed for nitrate by ion chromatography. Although the excretion of nitrate was markedly stimulated by LPS treatment, there were no significant effects of protein source or arginine supplementation of the diet.