L-arginine and nitric oxide-related compounds in plasma: comparison of normal and arginine-free diets in a 24-h crossover study.

The amino acid l-arginine is the precursor of nitric oxide (NO), a powerful vasodilator with antiplatelet properties. The availability of l-arginine has been suggested to be a rate-limiting factor in the production of NO in conditions such as hypercholesterolemia. It was speculated that fluctuations in plasma concentrations of l-arginine during the day may be dependent upon dietary intake of the amino acid, or other variables, and might modify the elaboration of endogenous NO. Over a 24-h period, the plasma concentrations of l-arginine and NO-related compounds (NOx) were measured during an l-arginine and nitrate/nitrite-free diet (diet A) or a nitrate/nitrite-free diet with a fixed amount of l-arginine intake (3.8 g/d) (diet B) in eight healthy volunteers during a 2-day crossover study. Subjects were randomly selected to begin with diet A or diet B and consumed the other diet on the second day. During diet A, plasma l-arginine decreased significantly from 09.00 to 16.00 (21.4 ± 2.0 to 11.9 ± 1.1 mg/ml), r...