EVIDENCE FOR THE INDUCTION OF URIDINE AND DEOXY-URIDINE PHOSPHORYLASES OF REGENERATING RAT LIVER IN VITRO

Abstract

Increases in the specific activities of undine and deoxyuridine phosphorylases of slices of regenerating rat liver were found 4 hours after incubation in tissue-culture medium containing uridine or 6-azauridine. These increases were not found when the tissue-culture medium contained either 8-azaguanine or puromycin, or when it lacked amino acids. Although both uridine and 6-azauridine were more effective in increasing the specific activity of uridine phosphorylase than that of deoxyuridine phosphorylase, azauridine was more effective than uridine in increasing the specific activities of both enzymes.In time studies, in which slices of regenerating rat liver were incubated in tissue-culture medium containing optimal concentrations of uridine, the specific activities of the two enzymes reached maximum levels at 3–4 hours. Puromycin prevented these increases.