Diurnal Changes in Uric Acid Metabolism

Abstract

The influence of dietary composition on uric acid metabolism was studied in the rat, and experimental results are summarized as follows: (1) The circadian variation of serum uric acid was observed in rats fed on a 25% casein diet. When rats were fed freely on a 25% casein diet, the level of serum uric acid was highest at 2 p. m. and lowest at 2 a. m. On the other hand, the circadian rhythm of enzyme activity was observed both in rats fed on a 25% and 70% casein diet. That is, the activity of xanthine oxidase showed a circadian variation with the same pattern as that of uric acid. Uricase activity exhibited a circadian fluctuation, with the highest: activity at 10 a. m. and the lowest at 6 p. m. (2) With yeast diet, serum uric acid showed a trough at 6 p. m. and a peak at 6 a. m. and the phase of the rhythm shifted with respect to that of rats fed on a 25% casein diet. The circadian rhythm was also observed in guanine deaminase activity.