Measurement of xanthine oxidase activity in some human tissues. An optimized method.

Xanthine oxidase activity in human liver or jejunum homogenates was measured by using 8-14C-hypoxanthine (HX) as a substrate. Products of oxidation were separated by thin-layer chromatography on MN Polygram cellulose and located by autoradiography. The percentage of oxidation was measured by liquid scintillation. Main parameters of the enzyme reaction have been optimized. Repeatability and reproducibility of the overall procedure give a variation coefficient of 6.3 and 7.7%, respectively. Minimal detectable enzymatic activity corresponds to an oxidation percentage of 1% (HX) for liver and jejunum. The reliability and practicability of this method allow a rapid diagnosis of xanthine oxidase deficiency. Normal values obtained by this optimized method range between 25 and 42 mukat . kg-1 protein for liver and 18 and 40 mukat . kg-1 protein for jejunum.