Determination of serum and plasma uridine levels in mice, rats, and humans by high-pressure liquid chromatography

Abstract

Serum and plasma uridine levels in mice, rats, and humans were conveniently measured by reverse-phase high-pressure liquid chromatography. Human serum levels were in the range of 1.9 to 8.4 nmol/ml, rat serum levels ranged from 3.7 to 9.4 nmol/ml, and mouse serum levels measured 8.0 to 11.8 nmol/ml. Levels of uridine were the same in human plasma and serum; however, plasma from mice and rats was somewhat lower than serum in uridine content ranging from 1.7 to 4.1 nmol/ml in rats and 1.5 to 4.7 nmol/ml in mice. There was some variation in the individual human serum and rat plasma uridine levels throughout the day, but the values were within the normal range, and the variations had no set pattern. Withholding food for 16–24 h had no observable effect on serum uridine levels in mice and humans or on rat plasma levels. These results suggest that uridine levels are regulated and are not a direct reflection of dietary intake of uridine.