Cellular xanthine oxidase and uricase levels in leukemic and normal mouse leukocytes.

Abstract

Quantitative alterations in the purine catabolic enzyme, xanthine oxidase, have been observed in neoplasia and nonmalignant hyperplasia. A decrease in the xanthine oxidase level per cell during carcinogenesis in both liver and breast tumors has been reported (1, 8). Likewise, Bennett and associates ~ have shown that several experi- mental tumors are low in xanthine oxidase ac- tivity. In contrast, the rapid cellular proliferation during liver regeneration is associated with a dou- bling of the cellular xanthine oxidase levels (4). An elevated xanthine oxidase level is therefore characteristic of normal hyperplastic liver, whereas diminished xanthine oxidase levels seem to be characteristic of rapidly growing hepatoma and of other neoplasms. To determine whether the decrease in purine catabolic enzymes accompanying neoplasia is a general phenomenon, it is important to compare other rapidly growing normal tissues with their malignant counterparts. The experimental mouse ascitic leukemia LI~10 provides just such an ex- perimental opportunity. The xanthine oxidase and uricase activities of these leukemic cells were there- fore compared with those of rapidly developing lymphocytes derived from normal mouse spleen and with normal polymorphonuclear leukocytes. Since previous studies have demonstrated in- hibition of xanthine oxidase by pharmacological levels of 8-azaguanine