DETERMINATION OF PLASMA PURINE NUCLEOSIDE PHOSPHORYLASE-ACTIVITY BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A high-performance liquid chromatographic method was developed for the determination of plasma purine nucleoside phosphorylase activity. In this method, the reaction mixture consisted of 15 mu l of plasma and 2 85 mu l of 50 mM phosphate buffer (pH 7.4) containing 3.8 mM inosine a nd 0.15 mM o-4-isobutoxyphenyl)-4-methyl-5-thiazolecarboxylic acid (st rong xanthine oxidase inhibitor). After the reaction, the hypoxanthine produced was monitored to express plasma purine nucleoside phosphoryl ase activity. By this method, the activity of purine nucleoside phosph orylase was easily determined even with a small-volume plasma sample a nd despite its low activity in plasma. In addition, plasma purine nucl eoside phosphorylase activity can be accurately determined even if the plasma is turbid. As a result, we were able to measure plasma purine nucleoside phosphorylase activity in patients with gout or asthma and healthy subjects, whereby it was demonstrated that plasma purine nucle oside phosphorylase activity was higher in patients with asthma than i n either healthy subjects or patients with gout. (C) 1995 Academic Pre ss, Inc.