Abstract
It is well-known that chicken and rat are uricotelic and ureotelic animals, respectively.(1) Incorporation of 14C-serine into uric acid and allantoin by chicken liver and rat liver slices and hepatoma cells were studied in comparison. The radioactive carbon was incorporated remarkably into uric acid by chicken liver slices, but were little incorporated into uric acid and allantoin by rat liver slices. On the other hand, in the case of rat ascites hepatoma cells, a considerable amount of incorporation was observed as same as the case of chicken liver.(2) Urea cycle which is inherent in rat liver was not detected in these rat ascites hepatomas.(3) The observations mentioned above suggest that abnormal phylogenic gene expression occurs in some rat ascites hepatomas, upon assumption that genes for uric acid synthesizing enzymes and urea cycle enzymes in rat liver cells had been acquired in an earlier stage of evolution before differentiation of Ayes and Mammalia and that the expression of only the genes for uric acid synthesizing enzymes had been repressed in a successive stage. Abnormal gene expressions may exist in some hepatomas arising not only from ontogenic aspect but also from phylogenic aspect.
