THE HISTOCHEMICAL DEMONSTRATION OF URICASE ACTIVITY

The histochemical demonstration of uricase activity in rat and guinea pig liver is described. The technique depends upon the generation of H 2 O 2 during the uricase reaction. The liberated H 2 O 2 participates in a coupled peroxidatic oxidation of 3-amino-9-ethylcarbazole, resulting in the deposition of an insoluble red oxidation product at the sites of uricase activity. This activity appeared as small, discrete red granules througout the cytoplasm of hepatic parenchymal cells of the rat and guinea pig. The distribution was clearly different from that of acid phosphatase activity in similar sections, which appeared typically pericanalicular. These results are consistent with other data indicating that uricase is associated with microbodies in the rat liver, and that microbodies and lysosomes are separate entities.