Character of the stimulatory response of uridine kinase in rat livers to cycloheximide treatment.

Administration of cycloheximde to adult rats resulted in the enhancement of uridine kinase activity in the liver. The increase of enzyme activity was not affected by adrenal secretion or uptake of food. Actinomycin D, hydroxyurea and puromycin injected simultaneously with cycloheximide depressed the increase of enzyme activity. On the contrary, administration of 5-azacytidine following cycloheximide resulted in further enhancement of uridine kinase. While the half-time of template RNA for uridine kinase in control rat livers was 24 h, for cycloheximide-stimulated enzyme it was about 11 h. At higher dose levels cycloheximide leads to an increased incorporation of both uridine and orotic acid into liver RNA; however, this effect was not observed in the starved animals. The mechanism of action of cycloheximide is briefly mentioned.