Exogenous Arginine as the Precursor of Creatine in the Dog

Abstract

Of the substances normally present in the diet, structural relationships point to arginine as the most logical precursor of creatine and creatinine. In view of the recent work of Benedict and Osterberg, who fed creatine over long periods of time, and the confirmation of their work in man by Rose, Helming and Ellis, it seemed possible that earlier attempts to demonstrate that creatine may originate from exogenous arginine failed because the amino acid was administered over too short a period to observe any significant change in the excretion of creatine or creatinine. Therefore it was decided to study the effect of arginine on the creatine-creatinine elimination, when the arginine was fed daily to a dog over a period of several weeks. After the completion of the experiment, Hyde and Rose published the results of a similar study of prolonged administration of arginine to a normal man and woman. Although their results showed no evidence of the conversion of exogenous arginine to creatine or creatinine, they have suggested that other species, particularly the pig, may differ in their response to arginine feeding. Our results presented in Table I, with another species, the dog, confirm those of Hyde and Rose, in that oral administration of arginine for a period of 35 days failed to influence the excretion of urinary creatine or creatinine, although exogenous creatine (Periods XIII and XIV) in small amounts resulted in prompt increases in both these catabolites, thus confirming the earlier work of Benedict and Osterberg. Our experiment was carried out with a trained metabolism dog, female, of about 14 kg. weight. Urine was collected by catheterization daily and analyzed for creatine and creatinine by the standard micromethods of Folin.