Developmental Changes in the Activity of Xanthine Dehydrogenase and closely Related Enzyme in Chick Tissues: (chick...

Xanthine-oxidizing activities in the chick tissues were measured by a couple of assay procedures during development of chick embryo. With the usual assay using pterine and NAD+ , no detectable level of XDH activity was observed in the liver and little in the duodenum before hatching, whereas an appreciable activity was detected in the kidney of chick embryo. When assayed with xanthine and dichlorophenol indophenol, an XDH-like enzyme activity was significantly detected in the embryonic liver, while no further enhancement of the activity was detected in the kidney and duodenum. Electrophoregrams obtained with samples from various developmental stages, followed by activity staining with tetrazolium dye, supported the above results and revealed that the embryonic XDH-like enzyme is not distinguishable from XDH of adult tissue in molecular size. This XDH-like enzyme, pre-existing in the liver before hatching, however, exhibited no cross reaction with antibody against intact XDH. The nature of this material was discussed in comparison with deflavinated XDH.